6.7: Sterols
- Understand the core structure of steroids and sterols.
- Understand the structural features of cholesterol, its production, consumption, transport, and medical problems.
- Understand bile acids' structure features, their functions, and medical problems.
- Understand the structural features of steroid hormones, functions, abuses, and medical problems.
What are steroids?
Steroids are biologically active compounds that have a core structure composed of four fused rings in a specific configuration: three six-membered rings designated A, B, and C and one five-membered ring D, as Figure \(\PageIndex{1}\) right. Gonane has this core structure of steroids. Other steroids have gonane skeletons with some groups attached. For example, cholestane has methyl groups at positions 10 and 13 and an aliphatic chain at position 17. Cholesterol has the structure of cholestane. It is a biomarker found in rocks and petroleum deposits.
What are sterols?
Sterols are organic compounds derived from gonane with \(\ce{H}\) #3 replaced with an alcohol (\(\ce{-OH}\)) group. The sterols are a sub-class of steroids. The simplest sterol is the alcohol gonane shown in the figure on the right. Other sterols have other groups attached to the gonane structure.
Cholesterol
Cholesterol is the most abundant sterol found in animals. It is a structural component of animal cell membranes, a precursor for steroid hormones, bile acids, and vitamin D. Cholesterol has the \(\ce{C}\) skeleton of cholestane, with an \(\ce{-OH}\) group at position #3 and a \(\ce{C=C}\) bond at position 5 and 6, as shown in Figure \(\PageIndex{2}\).
Cholesterol sources and consumption
Cholesterol is biosynthesized from lanosterol, which, in turn, is synthesized from squalene, as described in the previous section. Cholesterol is synthesized in the liver using fats, proteins, and carbohydrates as raw materials. An average human weighing 68 kg synthesizes about 1000 mg of cholesterol daily. Food is also a source of cholesterol intake, as shown in the figure on the right. Typically about 307 mg of cholesterol intake is through food per day in the US. The liver reduces cholesterol production to adjust for the intake from food sources.
Cholesterol is amphiphilic like phospholipids and sphingolipids, with \(\ce{-OH}\) as a polar head and cholestane structure as a hydrophobic tail. The cholesterol molecule is stiff due to restricted movements around \(\ce{C-C}\) bonds locked in the cyclic structure.
Cholesterol is used in the cell membrane to impart rigidity to the ring -the higher the proportion of cholesterol in the cell membrane, the more rigid the membrane.
Usually, cholesterol is 30% of the cell membrane. It is involved in signaling and is found in the brain, plasma membrane, and myelin sheath of nerve cells. Cholesterol is a precursor to vitamin D and steroid hormones, including corticosteroids, such as cortisol and aldosterone, and sex hormones, such as progesterone, estrogens, and testosterone.
The liver recycles the excess cholesterol by converting it into bile acids stored in the gallbladder and excreted into the digestive tract. Bile acids emulsify fats in the food, which helps digest the food. About 50% of the excreted cholesterol is re-absorbed into the bloodstream by the small intestine.
Transport of cholesterol
Cholesterol is insoluble in water like other lipids. It is transported by the blood, which is water rich medium. Like soap carries greases in water during washing, lipoprotein transport glycerolipids and cholesterol in the body. The lipoproteins exist as particles suspended in blood. Glycerides and cholesteryl esters are in the core, and phospholipids, proteins (apolipoprotein), and cholesterol form the outer layer having their hydrophobic parts oriented outwards in contact with water, as illustrated in Figure \(\PageIndex{3}\).
Lipoproteins are classified based on their density, as shown in the figure on the right ( Copyright: Modified from İnfoCan at Turkish Wikipedia., FAL, via Wikimedia Commons, Public domain ). Their density is based on the proportion of proteins in them -the higher the proportion of proteins, the higher the density. They also have roles in the transportation process of cholesterol and lipids:
- Chylomicrons – Transport triglycerides from the small intestine to the liver.
- Very low-density lipoproteins (VLDL) - transport newly synthesized triglycerides from the liver to the fatty tissues.
- Intermediate-density lipoproteins (IDL) are between VLDL and LDL in density. They are not usually seen in the blood.
- Low-density lipoproteins (LDL) - carry cholesterol from the liver to other tissues. They are also sometimes referred to as " bad cholesterol ."
- High-density lipoproteins (HDL) - collect cholesterol from other tissues and return it to the liver. They are sometimes referred to as " good cholesterol ."
Excessive fats and cholesterol in the body are associated with diabetes; cancers of the breast, pancreas, and colon; heart attack; and stroke. Lipoproteins transport cholesterol and fats in the body. LDLs transport cholesterol from the liver to the cells where they are needed, and HDLs transport surplus cholesterol back to the liver, where it is converted to other steroids and bile acids. If the LDL level is too high, some cholesterol is deposited in the artery as plagues, as shown in Figure \(\PageIndex{4}\). That is why LDLs are sometimes called bad cholesterol . The plaque causes inflammation and death of the tissue in that area and restricts blood flow. It may lead to a heart attack if the blood flow to the heart is inadequate or a stroke if the blood flow to the brain is insufficient.
Since HDLs transport the surplus cholesterol back to the liver for recycling and avoid plaque formation, HDLs are also called good cholesterol. The HDL levels must be sufficiently high to prevent a heart attack. A lipid panel test is prescribed to assess the risk of a heart attack. It measures the levels of total cholesterol, LDLs, HDLs, and triglycerides in the blood. The normal levels are the following.
| Total cholesterol | About 150 mg/dL, less is better |
| LDL ("bad") cholesterol | About 100 mg/dL, less is better |
| HDL ("good") cholesterol | At least 40 mg/dL in men and 50 mg/dL in women; higher is better |
| Triglycerides | Less than 150 mg/dL, less is better |
Bile salts
Bile salts are synthesized from cholesterol in the liver. First, additional \(\ce{-OH}\) groups are incorporated, and the alkyl side chain is shortened and oxidized to a carboxylic acid (\(\ce{-COOH}\)) group. Then the \(\ce{-COOH}\) group is esterified with either glycine or taurine that imparts a negative charge group, as illustrated in Figure \(\PageIndex{5}\).
Bile salts act like soaps with an ionic head and the remaining hydrophobic part. They are stored in the gallbladder and released into the small intestine, where they emulsify fats, i.e., convert the larger fat drops into smaller droplets, just like greases and dirt are emulsified by soaps. The smaller droplets have a larger surface area, increasing the fats' reaction rate with the pancreatic lipase enzymes, as illustrated in Figure \(\PageIndex{6}\).
Since bile salts are excreted with the feces, they remove cholesterol in two ways: 1) they are themselves the products of cholesterol, and 2) they dissolve cholesterol in the form of bile salt-cholesterol particles that are eliminated.
When a large amount of cholesterol accumulates in the gallbladder, it turns into solid particles, i.e., gallstones. The gallstones are almost 100% cholesterol with a small amount of calcium salts, glycerophospholipids, and fatty acids. Small gallstones pass through the bile duct and enter the duodenum, i.e., the initial part of the small intestine, and are excreted. However, large gallstones may get stuck in the bile duct and cause pain, as illustrated in Figure \(\PageIndex{7}\). If a gallstone block the bile duct, the bile can not be excreted. Then the bile pigment, known as bilirubin, will back up into the liver and be passed via blood. It causes jaundice which gives a yellow color to the skin and whiteness to the eyes.
Steroid hormones
Steroid hormones have structural similarities with cholesterol and are derived from it. Two significant subclasses of steroid hormones are sex and adrenocortical hormones, described in the following sections.
 The female sex hormones are estrogens, e.g., estradiol and estrone, and progestins, e.g., progesterone. These five of the most essential sex hormones are shown in the figure below. All five are present in males and females, but androgens are produced more in males, and estrogens and progestins are produced more in females.
  Estrogens and progestins control the development of female secondary sex characteristics. Estrogens increase the size of the uterus, deposit fat in the breasts, and broaden the pelvis of females. Progestins prepare the uterus for nurturing the fertilized egg. If the egg is not fertilized, the levels of estrogens and progestins drop sharply, and menstruation begins.
The release of estrogens and progestins during pregnancy prevents ovulation. This is mimicked by synthetic estrogens, such as ethynyl estradiol, and synthetic progestins, such as norethindrone, shown below, used in birth control formulations. As with the use of any steroid hormones, there are risks associated with synthetic hormones for birth control, including weight gain and a greater chance of forming blood clots.
Ethynyl estradiol
Norethindrone
One physiological function of testosterone is increasing muscle mass and decreasing body fat. Several synthetic equivalents, called anabolic steroids, have been developed for use as appearance and performance-enhancing drugs , as shown in the figure below. Although there are some benefits of anabolic steroids, their harmful effects are numerous and outweigh their benefits. They may not produce a euphoric high but develop substance use disorder. They can cause early heart attacks, strokes, kidney failure, liver tumors, make pimples pop up, hair fallout, grow breasts, and reduced testicles in males, grow beards in females, and cause extreme mood changes that may lead to committing suicide. Some of these harmful effects are related to the changes in cholesterol levels, causing an increase in low-density lipoprotein (bad cholesterol), a decrease in high-density lipoprotein (good cholesterol), high blood pressure, and liver damage. The harmful effects are long-lasting and may be irreversible.
Adrenocortical hormones
Adrenocortical hormones are produced by adrenal glands on the top of the kidneys, as shown in the figure on the right ( Copyright; Alan Hoofring (Illustrator), Public domain, via Wikimedia Commons ). There are two major subclasses: mineralocorticoids which regulate \(\ce{Na^{+}}\) and \(\ce{K^{+}}\) ions, and glucocorticoids which control carbohydrate metabolism.
Mineralocorticoid
Aldosterone is an important mineralocorticoid that enhances the reabsorption of \(\ce{Na^{+}}\) and \(\ce{K^{+}}\) ions in the kidney tubules. The control of \(\ce{Na^{+}}\) and \(\ce{K^{+}}\) concentrations controls water absorption and swelling of tissues.
glucocorticoid
Cortisone is a glucocorticoid that increases blood glucose levels and glycogen synthesis in the liver. Cortisol is another glucocorticoid released under stress to increase blood glucose levels at the expense of the metabolism of carbohydrates, fats, and proteins.
These hormones or their synthetic derivative, such as prednisone, shown below, are used to reduce inflammation, asthma, and arthritis. As with the use of steroids in general, health problems can result if these steroids are used for the long term.
Aldosterone
Cortisone
Cortisol
Prednisone (a synthetic corticoid)


5.14: Increasing Impact with Media
Learning Outcome
- Identify effective use of visual media in presentations, documents, spreadsheets, and messages
Speakers don’t need visual media to make a point. Just watch any stand-up comedian, and you’ll see that an engaging message can be delivered with nothing but a good story and a funny punchline.
Still, Microsoft PowerPoint and Apple Keynote offer speakers the opportunity to reinforce their messages visually, and, done right, this can have a powerful impact. Still, often, PowerPoint presentations are not done as well as they could be. We’ll learn more about making effective slide decks in Module 8: Developing and Delivering Business Presentations.
If you Google “PowerPoint bad,” you get over ninety million results. It’s been fashionable for a while to bash presentation software—especially PowerPoint—as stultifying or boring. But as anyone who’s seen the classroom scene in Ferris Bueller’s Day Off knows, bad presentations didn’t start with PowerPoint.
If you try to pound a nail in with the claw side of a hammer—or worse yet, with the handle of a screwdriver—do you blame the tool? No, of course not. Blaming PowerPoint for dull presentations and even duller presenters doesn’t get at the core issue. Even when the software could practically construct the presentation for you, you still need to focus on the best ways to present your message to your audience in the most effective way possible, including relevant visuals as needed.
There are a few key things to remember when creating visuals that you’re going to use to present to an audience. If you work on formulating satisfying answers and goals, your presentation should be effective and persuasive.
Everything we’ve discussed up to now about audience analysis and honing your message applies to the process of creating visuals for your spoken presentations. In addition, you will want to keep two other key points in mind:
- Unlike the exchange between audience and recipient that happens with an email or report, presentations happen in real time, so you want to be respectful of your audience’s time and not waste it.
- The best thing that can be said about a business presentation is that it was effective and helped everyone in the room do their work. If after the presentation, people are talking about how gorgeous your slides are or how funny you were, rather than about the topic of your presentation, you might not have been focused on the important aspects of your task.
One more critical question to ask yourself is this: are you delivering a speech or giving a business presentation?
If you are giving a speech—where you expect no back-and-forth conversation with your audience—then you probably don’t need visuals at all. Obviously, if you’re giving a speech about the details of an ancient Roman sculpture, it helps to show a picture, but speeches are scripted and rehearsed, so you don’t absolutely need words or images on your screen for you or for your audience. We’ll talk more about speeches in Module 7: Public Speaking.
If you are giving a business presentation, you might need visuals to help both you and your audience stay on track. There are a few rules for this that we can sketch out here, so you’ll be prepared for Module 8.
- A brief agenda slide lets the audience know you have a plan in mind. Give them a sense of the big chunks of information you’re going to cover so they trust you with their time and believe you know what you’re talking about. Deliver the agenda quickly and resist the temptation to elaborate on it. That’s what the rest of your presentation is for. Delivering a slide like the one below should take no more than thirty seconds.
-
Using images to convey your message can be really effective, especially if the images apply to your content, such as charts, graphs, and pictures of products or displays. Keep in mind that . . .
- Simple is good. If you need to present only a few data points from a graph that has several, delete or gray out the ones you don’t need in order to help your audience focus on what’s important.
- Pictures should be well-edited and as sharp as possible. If you need to show a detail from a larger picture, edit down to the detail you need and show that. Your audience will mentally check-out if they can’t see or follow what you’re talking about.
- A descriptive slide title helps remind your audience of what they’re looking at. If an audience member zones out while you introduce the slide, without a slide title, they’ll be lost when they come back into focus.
- Pictures are great for eliciting emotion if that’s what you want to do. A discussion of how good customer service changed the life of one of your customers is expected to get an emotional response, so use pictures of the customer, of their letter to management, or other images that will get at the emotion you want to generate. However, when you’re simply presenting a quarterly earnings report, emotion-generating pictures will be perceived as confusing or manipulative. This doesn’t mean you can’t have strong feelings about a strong quarter. It just means that the feeling will come through in how you deliver your message rather than through pictures.
 This means that they should help you stay on track and remind you of what you want to say. Therefore,
- Ignore those who say you shouldn’t read your slides. The words you put on a slide should be so brief that your audience doesn’t even notice you’re reading them. Rather, what’s on the slide will remind you of what you want to talk about in detail. As soon as you turn away from the slide and re-engage with your audience to elaborate on your point, they will be there with you—focused and learning. Watch the video following this list for a good explanation of how to read what’s on your slides without losing your audience.
- Putting on your slides the few words you need to stay on track eliminates the need for notes. More than anything, notes get in the way of engaging with your audience and staying on track. Presenters who use notes tend to either get mesmerized by them (especially if they’re on a small screen like a laptop or tablet) or they try to toggle between their notes and their audience, which is at best an awkward kind of yo-yoing act that steals focus from the point you’re trying to make.
- Remember, there is no award given for the longest presentation given with the fewest slides. It is loads better to make more slides with less on each of them. It helps you stay on track, and it gives your audience something new to focus on more frequently.
Remember the visual media standards when choosing your supporting images, charts, and video. Images should be very simple and clear, they should still be uniform, and they should support your company’s brand and be relevant to the points the speaker is trying to make. Most importantly, they should be effective and persuasive. There’s no better way to educate and persuade your audience than to be right in front of them.
If you are going to include images in a file to be sent electronically—a Word doc, a PowerPoint, or even an email—there are a few things to keep in mind. First of all, image files can be so large that they slow down the speed at which your document downloads and/or opens. This can be really annoying for your recipient, especially if they’re working on a phone or tablet and using up their data allowance. Sometimes, these files won’t even arrive because the system can’t handle them. There is a lot of information online about how to reduce image file sizes. Also keep in mind that if your recipient is reading your report or message on a small screen like a tablet or phone, the actual photo dimensions matter. In Module 8: Developing and Delivering Business Presentations, you can find information on how to resize images. Finally, since images can cause some technical trouble, include them in your documents only if they are necessary to support the points you are making. If they’re merely decorative, delete.


7.7: Form
- A basic introduction to recognizing form in music.
Form is the Basic Structure
Every piece of music has an overall plan or structure, the "big picture", so to speak. This is called the form of the music.
It is easy to recognize and grasp the form of some things, because they are small and simple, like a grain of salt, or repetitive, like a wall made of bricks of the same size. Other forms are easy to understand because they are so familiar; if you see dogs more often than you do sea cucumbers, it should be easier for you to recognize the form of an unfamiliar dog than of an unfamiliar sea cucumber. Other things, like a forest ecosystem, or the structure of a government, are so complex that they have to be explored or studied before their structure can be understood.
Musical forms offer a great range of complexity. Most listeners will quickly grasp the form of a short and simple piece, or of one built from many short repetitions. It is also easier to recognize familiar musical forms. The average American, for example, can distinguish easily between the verses and refrain of any pop song, but will have trouble recognizing what is going on in a piece of music for Balinese gamelan. Classical music traditions around the world tend to encourage longer, more complex forms which may be difficult to recognize without the familiarity that comes from study or repeated hearings.
You can enjoy music without recognizing its form, of course. But understanding the form of a piece helps a musician put together a more credible performance of it. Anyone interested in music theory or history, or in arranging or composing music, must have a firm understanding of form. And being able to "see the big picture" does help the listener enjoy the music even more.
Describing Form
Musicians traditionally have two ways to describe the form of a piece of music. One way involves labelling each large section with a letter. The other way is to simply give a name to a form that is very common.
Labeling Form With Letters
Letters can be used to label the form of any piece of music, from the simplest to the most complex. Each major section of the music is labelled with a letter; for example, the first section is the A section. If the second section (or third or fourth) is exactly the same as the first, it is also labelled A. If it is very much like the A section, but with some important differences, it can be labelled A' (pronounced "A prime"). The A' section can also show up later in the piece, or yet another variation of A, A'' (pronounced "A double prime") can show up, and so on.
The first major section of the piece that is very different from A is labelled B, and other sections that are like it can be labelled B, B', B'', and so on. Sections that are not like A or B are labelled C, and so on.
How do you recognize the sections? With familiar kinds of music, this is pretty easy. (See Figure 1 for some examples of forms that will be familiar to most listeners.) With unfamiliar types of music, it can be more of a challenge. Whether the music is classical, modern, jazz, or pop, listen for repeated sections of music. Also, listen for big changes, in the rhythm , melody , harmony , texture , and timbre . A new section that is not a repetition will usually have noticeable differences in more than one of these areas. For an excellent discussion of form, with plenty of chances to practice hearing the beginnings of new sections, please see Professor Brandt's Sound Reasoning course. In particular, Musical Form deals with recognizing when something new is being introduced (A/B instead of A only), and Time's Effect on the Material deals with recognizing when a section reappears changed (A', B', or A'').
Some Familiar Forms
Practice identifying some easy musical forms. Pick some favorite songs and listen to each repeatedly until you are satisfied that you have identified its full form using letters and primes. Compare the forms of the tunes to spot similarities and differences.
Listen for:
- Verses have the same melody but different words.
- Refrains have the same melody and the same words.
- Bridge Sections are new material that appears late in the song, usually appearing only once or twice, often in place of a verse and usually leading into the refrain. (You may want to note the differences - and the similarity - in the use of the term bridge by popular musicians and jazz musicians; see below ).
- Instrumentals are important sections that have no vocals. They can come at the beginning or end, or in between other sections. Is there more than one? Do they have the same melody as a verse or refrain? Are they similar to each other?
Solution
Your answers will depend on the songs you choose. Check them with a teacher if you can. (Bring the music so the teacher can listen to it while checking your answers.)
While discussing a piece of music in detail, musicians may also use letters to label smaller parts of the piece within larger sections, even down to labelling individual phrases . For example, the song "The Girl I Left Behind" has many verses with no refrain, an A A' A''- type form. However, a look at the tune of one verse shows that within that overall form is an A A' B A'' phrase structure.
Phrase Structure in "The Girl I Left Behind"
Now try labeling the phrases of a verse or a refrain of some of the songs you listened to in Exercise 1. Listen for phrases that use similar melodies. (Sometimes, but not always, they even use the same words.) How many of your refrains and verses were basically A A B A? What were the others?
Solution
If one is available, have a music teacher check your answers.
Naming Forms
Often a musical form becomes so popular with composers that it is given a name. For example, if a piece of music is called a "theme and variations", it is expected to have an overall plan quite different from a piece called a "rondo". (Specifically, the theme and variations would follow an A A' A'' A'''... plan, with each section being a new variation on the theme in the first section. A rondo follows an A B A C A ... plan, with a familiar section returning in between sections of new music.)
Also, many genres of music tend to follow a preset form, like the "typical pop song form" in Figure 1. A symphony, for example, is usually a piece of music written for a fairly large number of instruments. It is also associated with a particular form, so knowing that a piece of music is called a symphony should lead you to expect certain things about it. For example, listeners familiar with the symphonic form expect a piece called a symphony to have three or four (depending on when it was written) main sections, called movements. They expect a moment of silence in between movements, and also expect the movements to sound very different from each other; for example if the first movement is fast and loud, they might expect that the second movement would be slow and quiet. If they have heard many symphonies, they also would not be at all surprised if the first movement is in sonata form and the third movement is based on a dance.
Although a large group of people who play classical music together is often called a symphony, the more accurate term for the group is orchestra. The confusion occurs because many orchestras call themselves "symphony orchestras" because they spend so much time playing symphonies (as opposed to, for example, an "opera orchestra" or a "pops orchestra")
Other kinds of music are also so likely to follow a particular overall plan that they have become associated with a particular form. You can hear musicians talk about something being concerto form or sonata form, for example (even if the piece is not technically a concerto or sonata). Particular dances (a minuet, for example), besides having a set tempo and time signature , will sometimes have a set form that suits the dance steps. And many marches are similar enough in form that there are names for the expected sections (first strain, second strain, trio, break strain).
But it is important to remember that forms are not sets of rules that composers are required to follow. Some symphonies don't have silence between movements, and some don't use the sonata form in any of their movements. Plenty of marches have been written that don't have a trio section, and the development section of a sonata movement can take unexpected turns. And hybrid forms, like the sonata rondo, can become popular with some composers. After all, in architecture, "house" form suggests to most Americans a front and back door, a dining room off the kitchen, and bedrooms with closets, but an architect is free to leave out the dining room, and put the main door at the side of the house and the closets in the bathrooms. Whether a piece of music is a march, a sonata, or a theme and variations, the composer is always free to experiment with the overall architecture of the piece.
Being able to spot that overall architecture as we listen - knowing, so to speak, which room we are in right now - gives us important clues that help us understand and appreciate the music.
Some Common Forms
- Through-composed - One section (usually not very long) that does not contain any large repetitions. If a short piece includes repeated phrases, it may be classified by the structure of its phrases.
- Strophic - Composed of verses. The music is repeated sections with fairly small changes. May or may not include a refrain .
- Variations - One section repeated many times. Most commonly, the melody remains recognizable in each section, and the underlying harmonic structure remains basically the same, but big changes in rhythm , tempo , texture , or timbre keep each section sounding fresh and interesting. Writing a set of variations is considered an excellent exercise for students interested in composing, arranging, and orchestration.
- Jazz standard song form - Jazz utilizes many different forms, but one very common form is closely related to the strophic and variation forms. A chord progression in A A B A form (with the B section called the bridge ) is repeated many times. On the first and last repetition, the melody is played or sung, and soloists improvise during the other repetitions. The overall form of verse-like repetition, with the melody played only the first and final times, and improvisations on the other repetitions, is very common in jazz even when the A A B A song form is not being used.
- Rondo - One section returns repeatedly, with a section of new music before each return. (A B A C A ; sometimes A B A C A B A)
- Dance forms - Dance forms usually consist of repeated sections (so there is plenty of music to dance to), with each section containing a set number of measures (often four, eight, sixteen, or thirty-two) that fits the dance steps. Some very structured dance forms (Minuet, for example) are associated even with particular phrase structures and harmonic progressions within each section.
- Binary Form - Two different main sections (A B). Commonly in Western classical music, the A section will move away from the tonic , with a strong cadence in another key, and the B section will move back and end strongly in the tonic.
- Ternary Form - Three main sections, usually A B A or A B A'.
- Cyclic Form - There are two very different uses of this term. One refers to long multimovement works (a "song cycle", for example) that have an overarching theme and structure binding them together. It may also refer to a single movement or piece of music with a form based on the constant repetition of a single short section. This may be an exact repetition (ostinato) in one part of the music (for example, the bass line, or the rhythm section), while development, variation, or new melodies occur in other parts. Or it may be a repetition that gradually changes and evolves. This intense-repetition type of cyclic form is very common in folk musics around the world and often finds its way into classical and popular musics, too.
- Sonata form - may also be called sonata-allegro or first-movement form. It is in fact often found in the first movement of a sonata, but it has been an extremely popular form with many well-known composers, and so can be found anywhere from the first movement of a quartet to the final movement of a symphony. In this relatively complex form (too complex to outline here), repetition and development of melodic themes within a framework of expected key changes allow the composer to create a long movement that is unified enough that it makes sense to the listener, but varied enough that it does not get boring.


11.12: Rapid Cycling Between Coding and Testing
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If you think about the exercises we’ve done so far, you’ll realize that we started with an extremely simple script ( Script1.m ) that simply loaded a file, improved it ( Script2.m and Script2b.m ), and then added a bit more functionality ( Script3.m and Script4.m ). This is a good way to learn, but it’s also the way you should write your scripts. Don’t try to write 30 lines of code (or an entire script) without doing any testing along the way. If you write a 30-line script, you will probably have 8 different errors in the script, and it will be really hard to figure out what’s going wrong.
Instead, the best approach is to write a small amount of code, test it, debug it if necessary, and then add more code. At this point, you should be adding only 1-3 lines of code at a time. As you gain experience, you can write more lines before testing, but even an experienced programmer usually does some testing after every 20-40 new lines of code.
I almost put this piece of advice in a text box, but I decided that it's so important it deserves it's own section!


5.2: What is evolutionary correlation?
There is sometimes a bit of confusion among beginners as to what, exactly, we are doing when we carry out a comparative method, especially when testing for character correlations. Common language that comparative methods “control for phylogeny” or “remove the phylogeny from the data” is not necessarily enlightening or even always accurate. Another common suggestion is that species are not statistically independent and that we must account for that with comparative methods. While accurate, I still don’t think this statement fully captures the tree-thinking perspective enabled by comparative methods. In this section, I will use the particular example of correlated evolution to try to illustrate the power of comparative methods and how they differ from standard statistical approaches that do not use phylogenies.
In statistics, two variables can be correlated with one another. We might refer to this as a standard correlation . When two traits are correlated, it means that given the value of one trait – say, body size in mammals – one can predict the value of another – like home range area. Correlations can be positive (large values of x are associated with large values of y ) or negative (large values of x are associated with small values of y ). A surprisingly wide variety of hypotheses in biology can be tested by evaluating correlations between characters.
In comparative biology, we are often interested more specifically in evolutionary correlations . Evolutionary correlations occur when two traits tend to evolve together due to processes like mutation, genetic drift, or natural selection. If there is an evolutionary correlation between two characters, it means that we can predict the magnitude and direction of changes in one character given knowledge of evolutionary changes in another. Just like standard correlations, evolutionary correlations can be positive (increases in trait x are associated with increases in y ) or negative (decreases in x are associated with increases in y ).
We can now contrast standard correlations, testing the relationships between trait values across a set of species, with evolutionary correlations - where evolutionary changes in two traits are related to each other. This is a key distinction, because phylogenetic relatedness alone can lead to a relationship between two variables that are not, in fact, evolving together (Figure 5.1; also see Felsenstein 1985) . In such cases, standard correlations will, correctly, tell us that one can predict the value of trait y by knowing the value of trait x , at least among extant species; but we would be misled if we tried to make any evolutionary causal inference from this pattern. In the example of Figure 5.1, we can only predict x from y because the value of trait x tells us which clade the species belongs to, which, in turn, allows reasonable prediction of y . In fact, this is a classical example of a case where correlation is not causation: the two variables are only correlated with one another because both are related to phylogeny.
If we want to test hypotheses about trait evolution, we should specifically test evolutionary correlations 1 . If we find a relationship among the independent contrasts for two characters, for example, then we can infer that changes in each character are related to changes in the other – an inference that is much closer to most biological hypotheses about why characters might be related. In this case, then, we can think of statistical comparative methods as focused on disentangling patterns due to phylogenetic relatedness from patterns due to traits evolving in a correlated manner.


The first decision to be made in operationalizing a construct is to decide on what is the intended level of measurement.
Levels of measurement
, also called
rating scales
, refer to the values that an indicator can take (but says nothing about the indicator itself). For example, male and female (or M and F, or 1 and 2) are two levels of the indicator “gender.” In his seminal article titled "On the theory of scales of measurement" published in Science in 1946, psychologist Stanley Smith Stevens (1946) defined four generic types of rating scales for scientific measurements: nominal, ordinal, interval, and ratio scales. The statistical properties of these scales are shown in Table 6.1.
|
Scale
|
Central Tendency
|
Statistics
|
Transformations
|
|
Nominal
|
Mode
|
Chi-square
|
One-to-one (equality)
|
|
Ordinal
|
Median
|
Percentile, non-parametric statistics
|
Monotonic increasing (order)
|
|
Interval
|
Arithmetic mean, range, standard deviation
|
Correlation, regression, analysis of variance
|
Positive linear (affine)
|
|
Ratio
|
Geometric mean, harmonic mean
|
Coefficient of variation
|
Positive similarities (multiplicative, logarithmic)
|
|
Note: All higher-order scales can use any of the statistics for lower order scales.
|
Table 6.1. Statistical properties of rating scales
Nominal scales
, also called categorical scales, measure categorical data. These scales are used for variables or indicators that have mutually exclusive attributes. Examples include gender (two values: male or female), industry type (manufacturing, financial, agriculture, etc.), and religious affiliation (Christian, Muslim, Jew, etc.). Even if we assign unique numbers to each value, for instance 1 for male and 2 for female, the numbers don’t really mean anything (i.e., 1 is not less than or half of 2) and could have been easily been represented non-numerically, such as M for male and F for female. Nominal scales merely offer names or labels for different attribute values. The appropriate measure of central tendency of a nominal scale is mode, and neither the mean nor the median can be defined. Permissible statistics are chi-square and frequency distribution, and only a one-to-one (equality) transformation is allowed (e.g., 1=Male, 2=Female).
Ordinal scales
are those that measure
rank-ordered
data, such as the ranking of students in a class as first, second, third, and so forth, based on their grade point average or test scores. However, the actual or relative values of attributes or difference in attribute values cannot be assessed. For instance, ranking of students in class says nothing about the actual GPA or test scores of the students, or how they well performed relative to one another. A classic example in the natural sciences is Moh’s scale of mineral hardness, which characterizes the hardness of various minerals by their ability to scratch other minerals. For instance, diamonds can scratch all other naturally occurring minerals on earth, and hence diamond is the “hardest” mineral. However, the scale does not indicate the actual hardness of these minerals or even provides a relative assessment of their hardness. Ordinal scales can also use attribute labels (anchors) such as “bad”, “medium”, and “good”, or "strongly dissatisfied", "somewhat dissatisfied", "neutral", or "somewhat satisfied", and "strongly satisfied”. In the latter case, we can say that respondents who are “somewhat satisfied” are less satisfied than those who are “strongly satisfied”, but we cannot quantify their satisfaction levels. The central tendency measure of an ordinal scale can be its median or mode, and means are uninterpretable. Hence, statistical analyses may involve percentiles and non-parametric analysis, but more sophisticated techniques such as correlation, regression, and analysis of variance, are not appropriate. Monotonically increasing transformation (which retains the ranking) is allowed.
Interval scales
are those where the values measured are not only rank-ordered, but are also equidistant from adjacent attributes. For example, the temperature scale (in Fahrenheit or Celsius), where the difference between 30 and 40 degree Fahrenheit is the same as that between 80 and 90 degree Fahrenheit. Likewise, if you have a scale that asks respondents’ annual income using the following attributes (ranges): $0 to 10,000, $10,000 to 20,000, $20,000 to 30,000, and so forth, this is also an interval scale, because the mid-point of each range (i.e., $5,000, $15,000, $25,000, etc.) are equidistant from each other. The intelligence quotient (IQ) scale is also an interval scale, because the scale is designed such that the difference between IQ scores 100 and 110 is supposed to be the same as between 110 and 120 (although we do not really know whether that is truly the case). Interval scale allows us to examine “how much more” is one attribute when compared to another, which is not possible with nominal or ordinal scales. Allowed central tendency measures include mean, median, or mode, as are measures of dispersion, such as range and standard deviation. Permissible statistical analyses include all of those allowed for nominal and ordinal scales, plus correlation, regression, analysis of variance, and so on. Allowed scale transformation are positive linear. Note that the satisfaction scale discussed earlier is not strictly an interval scale, because we cannot say whether the difference between “strongly satisfied” and “somewhat satisfied” is the same as that between “neutral” and “somewhat satisfied” or between “somewhat dissatisfied” and “strongly dissatisfied”. However, social science researchers often “pretend” (incorrectly) that these differences are equal so that we can use statistical techniques for analyzing ordinal scaled data.
Ratio scales
are those that have all the qualities of nominal, ordinal, and interval scales, and in addition, also have a “true zero” point (where the value zero implies lack or nonavailability of the underlying construct). Most measurement in the natural sciences and engineering, such as mass, incline of a plane, and electric charge, employ ratio scales, as are some social science variables such as age, tenure in an organization, and firm size (measured as employee count or gross revenues). For example, a firm of size zero means that it has no employees or revenues. The Kelvin temperature scale is also a ratio scale, in contrast to the Fahrenheit or Celsius scales, because the zero point on this scale (equaling -273.15 degree Celsius) is not an arbitrary value but represents a state where the particles of matter at this temperature have zero kinetic energy. These scales are called “ratio” scales because the ratios of two points on these measures are meaningful and interpretable. For example, a firm of size 10 employees is double that of a firm of size 5, and the same can be said for a firm of 10,000 employees relative to a different firm of 5,000 employees. All measures of central tendencies, including geometric and harmonic means, are allowed for ratio scales, as are ratio measures, such as studentized range or coefficient of variation. All statistical methods are allowed. Sophisticated transformation such as positive similar (e.g., multiplicative or logarithmic) are also allowed.
Based on the four generic types of scales discussed above, we can create specific rating scales for social science research. Common rating scales include binary, Likert, semantic differential, or Guttman scales. Other less common scales are not discussed here.
Binary scales
. Binary scales are nominal scales consisting of binary items that assume one of two possible values, such as yes or no, true or false, and so on. For example, a typical binary scale for the “political activism” construct may consist of the six binary items shown in Table 6.2. Each item in this scale is a binary item, and the total number of “yes” indicated by a respondent (a value from 0 to 6) can be used as an overall measure of that person’s political activism. To understand how these items were derived, refer to the “Scaling” section later on in this chapter. Binary scales can also employ other values, such as male or female for gender, fulltime or part-time for employment status, and so forth. If an employment status item is modified to allow for more than two possible values (e.g., unemployed, full-time, part-time, and retired), it is no longer binary, but still remains a nominal scaled item.
|
Have you ever written a letter to a public official
|
Yes
|
No
|
|
Have you ever signed a political petition
|
Yes
|
No
|
|
Have you ever donated money to a political cause
|
Yes
|
No
|
|
Have you ever donated money to a candidate running for public office
|
Yes
|
No
|
|
Have you ever written a political letter to the editor of a newspaper or magazine
|
Yes
|
No
|
|
Have you ever persuaded someone to change his/her voting plans
|
Yes
|
No
|
Table 6.2. A six-item binary scale for measuring political activism
Likert scale
. Designed by Rensis Likert, this is a very popular rating scale for measuring ordinal data in social science research. This scale includes Likert items that are simply-worded statements to which respondents can indicate their extent of agreement or disagreement on a five or seven-point scale ranging from “strongly disagree” to “strongly agree”. A typical example of a six-item Likert scale for the “employment self-esteem” construct is shown in Table 6.3. Likert scales are summated scales, that is, the overall scale score may be a summation of the attribute values of each item as selected by a respondent.
|
|
Strongly Disagree
|
Somewhat Disagree
|
Neutral
|
Somewhat Agree
|
Strongly Agree
|
|
I feel good about my job
|
1
|
2
|
3
|
4
|
5
|
|
I get along well with others at work
|
1
|
2
|
3
|
4
|
5
|
|
I’m proud of my relationship with my supervisor at work
|
1
|
2
|
3
|
4
|
5
|
|
I can tell that other people at work are glad to have me there
|
1
|
2
|
3
|
4
|
5
|
|
I can tell that my coworkers respect me
|
1
|
2
|
3
|
4
|
5
|
|
I feel like I make a useful contribution at work
|
1
|
2
|
3
|
4
|
5
|
Table 6.3. A six-item Likert scale for measuring employment self-esteem
Likert items allow for more granularity (more finely tuned response) than binary items, including whether respondents are neutral to the statement. Three or nine values (often called “anchors”) may also be used, but it is important to use an odd number of values to allow for a “neutral” (or “neither agree nor disagree”) anchor. Some studies have used a “forced choice approach” to force respondents to agree or disagree with the LIkert statement by dropping the neutral mid-point and using even number of values and, but this is not a good strategy because some people may indeed be neutral to a given statement and the forced choice approach does not provide them the opportunity to record their neutral stance. A key characteristic of a Likert scale is that even though the statements vary in different items or indicators, the anchors (“strongly disagree” to “strongly agree”) remain the same. Likert scales are ordinal scales because the anchors are not necessarily equidistant, even though sometimes we treat them like interval scales.
|
How would you rate your opinions on national health insurance?
|
|
Very much
|
Somewhat
|
Neither
|
Somewhat
|
Very much
|
|
|
Good
|
□
|
□
|
□
|
□
|
□
|
Bad
|
|
Useful
|
□
|
□
|
□
|
□
|
□
|
Useless
|
|
Caring
|
□
|
□
|
□
|
□
|
□
|
Uncaring
|
|
Interesting
|
□
|
□
|
□
|
□
|
□
|
Boring
|
Table 6.4. A semantic differential scale for measuring attitude toward national health insurance
|
Semantic differential scale
. This is a composite (multi-item) scale where respondents are asked to indicate their opinions or feelings toward a single statement using different pairs of adjectives framed as polar opposites. For instance, the construct “attitude toward national health insurance” can be measured using four items shown in Table 6.4. As in the Likert scale, the overall scale score may be a summation of individual item scores. Notice that in Likert scales, the statement changes but the anchors remain the same across items. However, in semantic differential scales, the statement remains constant, while the anchors (adjective pairs) change across items. Semantic differential is believed to be an excellent technique for measuring people’s attitude or feelings toward objects, events, or behaviors.
Guttman scale
. Designed by Louis Guttman, this composite scale uses a series of items arranged in increasing order of intensity of the construct of interest, from least intense to most intense. As an example, the construct “attitude toward immigrants” can be measured using five items shown in Table 6.5. Each item in the above Guttman scale has a weight (not indicated above) which varies with the intensity of that item, and the weighted combination of each response is used as aggregate measure of an observation.
|
How will you rate your opinions on the following statements about immigrants?
|
|
Do you mind immigrants being citizens of your country
|
Yes
|
No
|
|
Do you mind immigrants living in your own neighborhood
|
Yes
|
No
|
|
Would you mind living next door to an immigrant
|
Yes
|
No
|
|
Would you mind having an immigrant as your close friend
|
Yes
|
No
|
|
Would you mind if someone in your family married an immigrant
|
Yes
|
No
|
Table 6.5. A five-item Guttman scale for measuring attitude toward immigrants


2.12: Career Technology Education (CTE)
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Career and Technical Education (CTE) prepares students for career pathways in the global marketplace by offering experiential learning, post-secondary credits and industry certifications.
CTE Students gain technical and high-level academic skills,equipping them to be lifelong learners. CTE provides each student with the opportunity to develop and refine skills and applications necessary to be productive citizens. The mission of CTE is to provide industry linked programs and services that enable all individuals to reach their career goals in order to achieve economic self-sufficiency,compete in the global marketplace, and contribute to a Nation's economic prosperity (WHAT IS CAREER TECHNICAL EDUCATION?, n.d.).
These certificate based programs are often thought to be equity measures to help students find a path that can provide them with sustainable skills that will garner them steady employment without high cost enrollment fees associated with some for profit CTE programs. Community Colleges nationwide offer a variety of programs to certificate students.
Career Technology Education (CTE) may include a diverse selection of certificate programs that allow the certificated person access to employment opportunities that require specific credentials. Because this field is so large and diverse, it is difficult to describe it as one succinct field. We have chosen to discuss just three specific fields offered at many community college CTE programs: Fire Technology, Graphic Design and Multimedia Studies.


5.E: Advanced Theories of Covalent Bonding (Exercises)
Molecular Structure and Polarity
Explain why the HOH molecule is bent, whereas the HBeH molecule is linear.
- Answer
-
The placement of the two sets of unpaired electrons in water forces the bonds to assume a tetrahedral arrangement, and the resulting HOH molecule is bent. The HBeH molecule (in which Be has only two electrons to bond with the two electrons from the hydrogens) must have the electron pairs as far from one another as possible and is therefore linear.
What feature of a Lewis structure can be used to tell if a molecule’s (or ion’s) electron-pair geometry and molecular structure will be identical?
- Answer
-
Add texts here. Do not delete this text first.
Explain the difference between electron-pair geometry and molecular structure.
- Answer
-
Space must be provided for each pair of electrons whether they are in a bond or are present as lone pairs. Electron-pair geometry considers the placement of all electrons. Molecular structure considers only the bonding-pair geometry.
Why is the H–N–H angle in NH 3 smaller than the H–C–H bond angle in CH 4 ? Why is the H–N–H angle in \(\ce{NH4+}\) identical to the H–C–H bond angle in CH 4 ?
- Answer
-
Add texts here. Do not delete this text first.
Explain how a molecule that contains polar bonds can be nonpolar.
- Answer
-
As long as the polar bonds are compensated (for example. two identical atoms are found directly across the central atom from one another), the molecule can be nonpolar.
As a general rule, MX n molecules (where M represents a central atom and X represents terminal atoms; n = 2 – 5) are polar if there is one or more lone pairs of electrons on M. NH 3 (M = N, X = H, n = 3) is an example. There are two molecular structures with lone pairs that are exceptions to this rule. What are they?
- Answer
-
Add texts here. Do not delete this text first.
Predict the electron pair geometry and the molecular structure of each of the following molecules or ions:
- SF 6
- PCl 5
- BeH 2
- \(\ce{CH3+}\)
- Answer
-
- Both the electron geometry and the molecular structure are octahedral.
- Both the electron geometry and the molecular structure are trigonal bipyramid.
- Both the electron geometry and the molecular structure are linear.
- Both the electron geometry and the molecular structure are trigonal planar.
Identify the electron pair geometry and the molecular structure of each of the following molecules or ions:
- \(\ce{IF6+}\)
- CF 4
- BF 3
- \(\ce{SiF5-}\)
- BeCl 2
- Answer
-
Add texts here. Do not delete this text first.
- What are the electron-pair geometry and the molecular structure of each of the following molecules or ions?
- ClF 5
- \(\ce{ClO2-}\)
- \(\ce{TeCl4^2-}\)
- PCl 3
- SeF 4
- \(\ce{PH2-}\)
- Answer
-
- electron-pair geometry: octahedral, molecular structure: square pyramidal
- electron-pair geometry: tetrahedral, molecular structure: bent
- electron-pair geometry: octahedral, molecular structure: square planar
- electron-pair geometry: tetrahedral, molecular structure: trigonal pyramidal
- electron-pair geometry: trigonal bypyramidal, molecular structure: seesaw
- electron-pair geometry: tetrahedral, molecular structure: bent (109°)
Predict the electron pair geometry and the molecular structure of each of the following ions:
- H 3 O +
- \(\ce{PCl4-}\)
- \(\ce{SnCl3-}\)
- \(\ce{BrCl4-}\)
- ICl 3
- XeF 4
- SF 2
- Answer
-
Add texts here. Do not delete this text first.
Identify the electron pair geometry and the molecular structure of each of the following molecules:
- ClNO (N is the central atom)
- CS 2
- Cl 2 CO (C is the central atom)
- Cl 2 SO (S is the central atom)
- SO 2 F 2 (S is the central atom)
- XeO 2 F 2 (Xe is the central atom)
- \(\ce{ClOF2+}\) (Cl is the central atom)
- Answer
-
- electron-pair geometry: trigonal planar, molecular structure: bent (120°)
- electron-pair geometry: linear, molecular structure: linear
- electron-pair geometry: trigonal planar, molecular structure: trigonal planar
- electron-pair geometry: tetrahedral, molecular structure: trigonal pyramidal
- electron-pair geometry: tetrahedral, molecular structure: tetrahedral
- electron-pair geometry: trigonal bipyramidal, molecular structure: seesaw
- electron-pair geometry: tetrahedral, molecular structure: trigonal pyramidal
Predict the electron pair geometry and the molecular structure of each of the following:
- IOF 5 (I is the central atom)
- POCl 3 (P is the central atom)
- Cl 2 SeO (Se is the central atom)
- ClSO + (S is the central atom)
- F 2 SO (S is the central atom)
- \(\ce{NO2-}\)
- \(\ce{SiO4^4-}\)
- Answer
-
Add texts here. Do not delete this text first.
- Which of the following molecules and ions contain polar bonds? Which of these molecules and ions have dipole moments?
- ClF 5
- \(\ce{ClO2-}\)
- \(\ce{TeCl4^2-}\)
- PCl 3
- SeF 4
- \(\ce{PH2-}\)
- XeF 2
- Answer
-
All of these molecules and ions contain polar bonds. Only ClF 5 , \(\ce{ClO2-}\), PCl 3 , SeF 4 , and \(\ce{PH2-}\) have dipole moments.
Which of the molecules and ions contain polar bonds? Which of these molecules and ions have dipole moments?
- H 3 O +
- \(\ce{PCl4-}\)
- \(\ce{SnCl3-}\)
- \(\ce{BrCl4-}\)
- ICl 3
- XeF 4
- SF 2
- Answer
-
Add texts here. Do not delete this text first.
Which of the following molecules have dipole moments?
- CS 2
- SeS 2
- CCl 2 F 2
- PCl 3 (P is the central atom)
- ClNO (N is the central atom)
- Answer
-
SeS 2 , CCl 2 F 2 , PCl 3 , and ClNO all have dipole moments.
Identify the molecules with a dipole moment:
- SF 4
- CF 4
- Cl 2 CCBr 2
- CH 3 Cl
- H 2 CO
- Answer
-
Add texts here. Do not delete this text first.
The molecule XF 3 has a dipole moment. Is X boron or phosphorus?
- Answer
-
P
The molecule XCl 2 has a dipole moment. Is X beryllium or sulfur?
- Answer
-
S
Is the Cl 2 BBCl 2 molecule polar or nonpolar?
- Answer
-
nonpolar
There are three possible structures for PCl 2 F 3 with phosphorus as the central atom. Draw them and discuss how measurements of dipole moments could help distinguish among them.
- Answer
-
Add texts here. Do not delete this text first.
Describe the molecular structure around the indicated atom or atoms:
- the sulfur atom in sulfuric acid, H 2 SO 4 [(HO) 2 SO 2 ]
- the chlorine atom in chloric acid, HClO 3 [HOClO 2 ]
- the oxygen atom in hydrogen peroxide, HOOH
- the nitrogen atom in nitric acid, HNO 3 [HONO 2 ]
- the oxygen atom in the OH group in nitric acid, HNO 3 [HONO 2 ]
- the central oxygen atom in the ozone molecule, O 3
- each of the carbon atoms in propyne, CH 3 CCH
- the carbon atom in Freon, CCl 2 F 2
- each of the carbon atoms in allene, H 2 CCCH 2
- Answer
-
- tetrahedral
- trigonal pyramidal
- bent (109°)
- trigonal planar
- bent (109°)
- bent (109°)
- CH 3 CCH tetrahedral, CH 3 CCH linear
- tetrahedral
- H 2 CCCH 2 linear, H 2 CCCH 2 trigonal planar
Draw the Lewis structures and predict the shape of each compound or ion:
- CO 2
- \(\ce{NO2-}\)
- SO 3
- \(\ce{SO3^2-}\)
- Answer
-
Add texts here. Do not delete this text first.
A molecule with the formula AB 2 , in which A and B represent different atoms, could have one of three different shapes. Sketch and name the three different shapes that this molecule might have. Give an example of a molecule or ion for each shape.
- Answer
-
A molecule with the formula AB 3 , in which A and B represent different atoms, could have one of three different shapes. Sketch and name the three different shapes that this molecule might have. Give an example of a molecule or ion that has each shape.
- Answer
-
Add texts here. Do not delete this text first.
- Draw the Lewis electron dot structures for these molecules, including resonance structures where appropriate:
- \(\ce{CS3^2-}\)
- CS 2
- CS
- Answer
-
Add texts here. Do not delete this text first.
- predict the molecular shapes for \(\ce{CS3^2-}\) and CS 2 and explain how you arrived at your predictions
(a)
(b)
(c)
- Answer
-
\(\ce{CS3^2-}\) includes three regions of electron density (all are bonds with no lone pairs); the shape is trigonal planar;
CS 2 has only two regions of electron density (all bonds with no lone pairs);
the shape is linear
What is the molecular structure of the stable form of FNO 2 ? (N is the central atom.)
- Answer
-
Add texts here. Do not delete this text first.
A compound with a molar mass of about 42 g/mol contains 85.7% carbon and 14.3% hydrogen. What is its molecular structure?
- Answer
-
Add texts here. Do not delete this text first.
Use the simulation to perform the following exercises for a two-atom molecule:
- Adjust the electronegativity value so the bond dipole is pointing toward B. Then determine what the electronegativity values must be to switch the dipole so that it points toward A.
- With a partial positive charge on A, turn on the electric field and describe what happens.
- With a small partial negative charge on A, turn on the electric field and describe what happens.
- Reset all, and then with a large partial negative charge on A, turn on the electric field and describe what happens.
Use the simulation to perform the following exercises for a real molecule. You may need to rotate the molecules in three dimensions to see certain dipoles.
- Sketch the bond dipoles and molecular dipole (if any) for O 3. Explain your observations.
- Look at the bond dipoles for NH 3 . Use these dipoles to predict whether N or H is more electronegative.
- Predict whether there should be a molecular dipole for NH 3 and, if so, in which direction it will point. Check the molecular dipole box to test your hypothesis.
- Answer
-
The molecular dipole points away from the hydrogen atoms.
Use the Molecule Shape simulator to build a molecule. Starting with the central atom, click on the double bond to add one double bond. Then add one single bond and one lone pair. Rotate the molecule to observe the complete geometry. Name the electron group geometry and molecular structure and predict the bond angle.
- Answer
-
Click the check boxes at the bottom and right of the simulator to check your answers.
Use the Molecule Shape simulator to explore real molecules. On the Real Molecules tab, select H 2 O. Switch between the “real” and “model” modes. Explain the difference observed.
- Answer
-
The structures are very similar. In the model mode, each electron group occupies the same amount of space, so the bond angle is shown as 109.5°. In the “real” mode, the lone pairs are larger, causing the hydrogens to be compressed. This leads to the smaller angle of 104.5°.
Use the Molecule Shape simulator to explore real molecules. On the Real Molecules tab, select “model” mode and S 2 O. What is the model bond angle? Explain whether the “real” bond angle should be larger or smaller than the ideal model angle.
- Answer
-
Add texts here. Do not delete this text first.
Valence Bond Theory
Explain how σ and π bonds are similar and how they are different.
- Answer
-
Similarities : Both types of bonds result from overlap of atomic orbitals on adjacent atoms and contain a maximum of two electrons. Differences : σ bonds are stronger and result from end-to-end overlap and all single bonds are σ bonds; π bonds between the same two atoms are weaker because they result from side-by-side overlap, and multiple bonds contain one or more π bonds (in addition to a σ bond).
Draw a curve that describes the energy of a system with H and Cl atoms at varying distances. Then, find the minimum energy of this curve two ways.
- Use the bond energy found in Table 8.2.1 to calculate the energy for one single HCl bond (Hint: How many bonds are in a mole?)
- Use the enthalpy of reaction and the bond energies for \(H_2\) and \(Cl_2\) to solve for the energy of one mole of HCl bonds. \[H_{2(g)}+Cl_{2(g)} \rightleftharpoons 2HCl_{(g)} \;\;\; ΔH^∘_{rxn}=−184.7\; kJ/mol\]
- Answer
-
When H and Cl are separate (the x axis) the energy is at a particular value. As they approach, it decreases to a minimum at 127 pm (the bond distance), and then it increases sharply as you get closer.
- (a) H–Cl431 kJ/mol 427kJmol×mol6.022×1023bonds×1000 JkJ=7.09×10−19
- (b) We know Hess’s law related to bond energies: ΔH°=ƩΔH∘BDE(broken)−ƩΔH∘BDE(formed) We are given the enthalpy of reaction
\[−184.7 kJ/mol=(ΔH∘BDE(H–H)+ΔH∘BDE(Cl–Cl))−(2ΔH∘BDE(H–Cl))\]
\[H–H is 436 kJ/mol and Cl–Cl is 243\]
\[–184.7 kJ/mol = (436 + 243) – 2x = 679 – 2x\]
\[2x = 863.7 kJ/mol\]
\[x = 432\; kJ/mol\]
This is very close to the value from part (a).
Explain why bonds occur at specific average bond distances instead of the atoms approaching each other infinitely close.
- Answer
-
The specific average bond distance is the distance with the lowest energy. At distances less than the bond distance, the positive charges on the two nuclei repel each other, and the overall energy increases.
Use valence bond theory to explain the bonding in F 2 , HF, and ClBr. Sketch the overlap of the atomic orbitals involved in the bonds.
- Answer
-
The single bond present in each molecule results from overlap of the relevant orbitals: F 2 p orbitals in F 2 , the H 1 s and F 2 p orbitals in HF, and the Cl 3 p orbital and Br 4 p orbital in ClBr.
Use valence bond theory to explain the bonding in O 2 . Sketch the overlap of the atomic orbitals involved in the bonds in O 2 .
- Answer
-
Bonding: One σ bond and one π bond. The s orbitals are filled and do not overlap. The p orbitals overlap along the axis to form a σ bond and side by side to form the π bond.
How many σ and π bonds are present in the molecule HCN?
- Answer
-
\(\ce{H–C≡N}\) has two σ (H–C and C–N) and two π (making the CN triple bond).
A friend tells you N 2 has three π bonds due to overlap of the three p -orbitals on each N atom. Do you agree?
- Answer
-
No, two of the p orbitals (one on each N) will be oriented end-to-end and will form a σ bond.
Draw the Lewis structures for CO 2 and CO, and predict the number of σ and π bonds for each molecule.
- CO 2
- CO
- Answer
-
(a) 2 σ 2 π;
(b) 1 σ 2 π;
Hybrid Atomic Orbitals
Why is the concept of hybridization required in valence bond theory?
- Answer
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Hybridization is introduced to explain the geometry of bonding orbitals in valance bond theory.Add texts here.
Give the shape that describes each hybrid orbital set:
(a) sp 2
(b) sp 3 d
(c) sp
(d) sp 3 d 2
- Answer
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Add texts here. Do not delete this text first.
Explain why a carbon atom cannot form five bonds using sp 3 d hybrid orbitals.
- Answer
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There are no d orbitals in the valence shell of carbon.
What is the hybridization of the central atom in each of the following?
(a) BeH 2
(b) SF 6
(c) \(\ce{PO4^3-}\)
(d) PCl 5
- Answer
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Add texts here. Do not delete this text first.
A molecule with the formula AB 3 could have one of four different shapes. Give the shape and the hybridization of the central A atom for each.
- Answer
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trigonal planar, sp 2 ; trigonal pyramidal (one lone pair on A) sp 3 ; T-shaped (two lone pairs on A sp 3 d , or (three lone pairs on A) sp 3 d 2
Methionine, CH 3 SCH 2 CH 2 CH(NH 2 )CO 2 H, is an amino acid found in proteins. Draw a Lewis structure of this compound. What is the hybridization type of each carbon, oxygen, the nitrogen, and the sulfur?
- Answer
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Sulfuric acid is manufactured by a series of reactions represented by the following equations:
\(\ce{S8}(s)+\ce{8O2}(g)⟶\ce{8SO2}(g)\)
\(\ce{2SO2}(g)+\ce{O2}(g)⟶\ce{2SO3}(g)\)
\(\ce{SO3}(g)+\ce{H2O}(l)⟶\ce{H2SO4}(l)\)
Draw a Lewis structure, predict the molecular geometry by VSEPR, and determine the hybridization of sulfur for the following:
(a) circular S 8 molecule
(b) SO 2 molecule
(c) SO 3 molecule
(d) H 2 SO 4 molecule (the hydrogen atoms are bonded to oxygen atoms)
- Answer
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(a) Each S has a bent (109°) geometry, sp 3
(b) Bent (120°), sp 2
(c) Trigonal planar, sp 2
(d) Tetrahedral, sp 3
Two important industrial chemicals, ethene, C 2 H 4 , and propene, C 3 H 6 , are produced by the steam (or thermal) cracking process:
\(\ce{2C3H8}(g)⟶\ce{C2H4}(g)+\ce{C3H6}(g)+\ce{CH4}(g)+\ce{H2}(g)\)
For each of the four carbon compounds, do the following:
(a) Draw a Lewis structure.
(b) Predict the geometry about the carbon atom.
(c) Determine the hybridization of each type of carbon atom.
- Answer
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Add texts here. Do not delete this text first.
For many years after they were discovered, it was believed that the noble gases could not form compounds. Now we know that belief to be incorrect. A mixture of xenon and fluorine gases, confined in a quartz bulb and placed on a windowsill, is found to slowly produce a white solid. Analysis of the compound indicates that it contains 77.55% Xe and 22.45% F by mass.
(a) What is the formula of the compound?
(b) Write a Lewis structure for the compound.
(c) Predict the shape of the molecules of the compound.
(d) What hybridization is consistent with the shape you predicted?
Answer
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(a) XeF 2
(b)
(c) linear
(d) sp 3 d
Consider nitrous acid, HNO 2 (HONO).
(a) Write a Lewis structure.
(b) What are the electron pair and molecular geometries of the internal oxygen and nitrogen atoms in the HNO 2 molecule?
(c) What is the hybridization on the internal oxygen and nitrogen atoms in HNO 2 ?
- Answer
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Add texts here. Do not delete this text first.
Strike-anywhere matches contain a layer of KClO 3 and a layer of P 4 S 3 . The heat produced by the friction of striking the match causes these two compounds to react vigorously, which sets fire to the wooden stem of the match. KClO 3 contains the \(\ce{ClO3-}\) ion. P 4 S 3 is an unusual molecule with the skeletal structure.
(a) Write Lewis structures for P 4 S 3 and the \(\ce{ClO3-}\) ion.
(b) Describe the geometry about the P atoms, the S atom, and the Cl atom in these species.
(c) Assign a hybridization to the P atoms, the S atom, and the Cl atom in these species.
(d) Determine the oxidation states and formal charge of the atoms in P 4 S 3 and the \(\ce{ClO3-}\) ion.
- Answer
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(a)
(b) P atoms, trigonal pyramidal; S atoms, bent, with two lone pairs; Cl atoms, trigonal pyramidal;
(c) Hybridization about P, S, and Cl is, in all cases, sp 3 ;
(d) Oxidation states P +1, S \(−1\dfrac{1}{3}\), Cl +5, O –2. Formal charges: P 0; S 0; Cl +2: O –1
Identify the hybridization of each carbon atom in the following molecule. (The arrangement of atoms is given; you need to determine how many bonds connect each pair of atoms.)
- Answer
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Add texts here. Do not delete this text first.
Write Lewis structures for NF 3 and PF 5 . On the basis of hybrid orbitals, explain the fact that NF 3 , PF 3 , and PF 5 are stable molecules, but NF 5 does not exist.
- Answer
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Phosphorus and nitrogen can form sp 3 hybrids to form three bonds and hold one lone pair in PF 3 and NF 3 , respectively. However, nitrogen has no valence d orbitals, so it cannot form a set of sp 3 d hybrid orbitals to bind five fluorine atoms in NF 5 . Phosphorus has d orbitals and can bind five fluorine atoms with sp 3 d hybrid orbitals in PF 5 .
In addition to NF 3 , two other fluoro derivatives of nitrogen are known: N 2 F 4 and N 2 F 2 . What shapes do you predict for these two molecules? What is the hybridization for the nitrogen in each molecule?
- Answer
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Add texts here. Do not delete this text first.
Multiple Bonds
The bond energy of a C–C single bond averages 347 kJ mol −1 ; that of a C≡C triple bond averages 839 kJ mol −1 . Explain why the triple bond is not three times as strong as a single bond.
- Answer
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Add texts here. Do not delete this text first.
A triple bond consists of one σ bond and two π bonds. A σ bond is stronger than a π bond due to greater overlap.
For the carbonate ion, \(\ce{CO3^2-}\), draw all of the resonance structures. Identify which orbitals overlap to create each bond.
- Answer
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Add texts here. Do not delete this text first.
A useful solvent that will dissolve salts as well as organic compounds is the compound acetonitrile, H 3 CCN. It is present in paint strippers.
(a) Write the Lewis structure for acetonitrile, and indicate the direction of the dipole moment in the molecule.
(b) Identify the hybrid orbitals used by the carbon atoms in the molecule to form σ bonds.
(c) Describe the atomic orbitals that form the π bonds in the molecule. Note that it is not necessary to hybridize the nitrogen atom.
- Answer
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(a)
(b) The terminal carbon atom uses sp 3 hybrid orbitals, while the central carbon atom is sp hybridized.
(c) Each of the two π bonds is formed by overlap of a 2 p orbital on carbon and a nitrogen 2 p orbital.
For the molecule allene, \(\mathrm{H_2C=C=CH_2}\), give the hybridization of each carbon atom. Will the hydrogen atoms be in the same plane or perpendicular planes?
- Answer
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Add texts here. Do not delete this text first.
Identify the hybridization of the central atom in each of the following molecules and ions that contain multiple bonds:
(a) ClNO (N is the central atom)
(b) CS 2
(c) Cl 2 CO (C is the central atom)
(d) Cl 2 SO (S is the central atom)
(e) SO 2 F 2 (S is the central atom)
(f) XeO 2 F 2 (Xe is the central atom)
(g) \(\ce{ClOF2+}\) (Cl is the central atom)
- Answer
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(a) sp 2 ; (b) sp ; (c) sp 2 ; (d) sp 3 ; (e) sp 3 ; (f) sp 3 d ; (g) sp 3
Describe the molecular geometry and hybridization of the N, P, or S atoms in each of the following compounds.
(a) H 3 PO 4 , phosphoric acid, used in cola soft drinks
(b) NH 4 NO 3 , ammonium nitrate, a fertilizer and explosive
(c) S 2 Cl 2 , disulfur dichloride, used in vulcanizing rubber
(d) K 4 [O 3 POPO 3 ], potassium pyrophosphate, an ingredient in some toothpastes
- Answer
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Add texts here. Do not delete this text first.
For each of the following molecules, indicate the hybridization requested and whether or not the electrons will be delocalized:
(a) ozone (O 3 ) central O hybridization
(b) carbon dioxide (CO 2 ) central C hybridization
(c) nitrogen dioxide (NO 2 ) central N hybridization
(d) phosphate ion (\(\ce{PO4^3-}\)) central P hybridization
- Answer
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(a) sp 2 , delocalized; (b) sp , localized; (c) sp 2 , delocalized; (d) sp 3 , delocalized
For each of the following structures, determine the hybridization requested and whether the electrons will be delocalized:
(a) Hybridization of each carbon
(b) Hybridization of sulfur
(c) All atoms
- Answer
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Add texts here. Do not delete this text first.
Draw the orbital diagram for carbon in CO 2 showing how many carbon atom electrons are in each orbital.
- Answer
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Each of the four electrons is in a separate orbital and overlaps with an electron on an oxygen atom.
Molecular Orbital Theory
Sketch the distribution of electron density in the bonding and antibonding molecular orbitals formed from two s orbitals and from two p orbitals.
How are the following similar, and how do they differ?
(a) σ molecular orbitals and π molecular orbitals
(b) ψ for an atomic orbital and ψ for a molecular orbital
(c) bonding orbitals and antibonding orbitals
- Answer
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(a) Similarities: Both are bonding orbitals that can contain a maximum of two electrons. Differences: σ orbitals are end-to-end combinations of atomic orbitals, whereas π orbitals are formed by side-by-side overlap of orbitals.
(b) Similarities: Both are quantum-mechanical constructs that represent the probability of finding the electron about the atom or the molecule. Differences: ψ for an atomic orbital describes the behavior of only one electron at a time based on the atom. For a molecule, ψ represents a mathematical combination of atomic orbitals.
(c) Similarities: Both are orbitals that can contain two electrons. Differences: Bonding orbitals result in holding two or more atoms together. Antibonding orbitals have the effect of destabilizing any bonding that has occurred.
If molecular orbitals are created by combining five atomic orbitals from atom A and five atomic orbitals from atom B combine, how many molecular orbitals will result?
- Answer
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Can a molecule with an odd number of electrons ever be diamagnetic? Explain why or why not.
- Answer
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An odd number of electrons can never be paired, regardless of the arrangement of the molecular orbitals. It will always be paramagnetic.
Can a molecule with an even number of electrons ever be paramagnetic? Explain why or why not.
- Answer
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Add texts here. Do not delete this text first.
Why are bonding molecular orbitals lower in energy than the parent atomic orbitals?
- Answer
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Bonding orbitals have electron density in close proximity to more than one nucleus. The interaction between the bonding positively charged nuclei and negatively charged electrons stabilizes the system.
Calculate the bond order for an ion with this configuration:
- Answer
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Add texts here. Do not delete this text first.
Explain why an electron in the bonding molecular orbital in the H 2 molecule has a lower energy than an electron in the 1 s atomic orbital of either of the separated hydrogen atoms.
- Answer
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The pairing of the two bonding electrons lowers the energy of the system relative to the energy of the nonbonded electrons.
Predict the valence electron molecular orbital configurations for the following, and state whether they will be stable or unstable ions.
(a) \(\ce{Na2^2+}\)
(b) \(\ce{Mg2^2+}\)
(c) \(\ce{Al2^2+}\)
(d) \(\ce{Si2^2+}\)
(e) \(\ce{P2^2+}\)
(f) \(\ce{S2^2+}\)
(g) \(\ce{F2^2+}\)
(h) \(\ce{Ar2^2+}\)
- Answer
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Add texts here. Do not delete this text first.
Determine the bond order of each member of the following groups, and determine which member of each group is predicted by the molecular orbital model to have the strongest bond.
(a) H 2 , \(\ce{H2+}\), \(\ce{H2-}\)
(b) O 2 , \(\ce{O2^2+}\), \(\ce{O2^2-}\)
(c) Li 2 , \(\ce{Be2+}\), Be 2
(d) F 2 , \(\ce{F2+}\), \(\ce{F2-}\)
- Answer
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(a) H 2 bond order = 1, \(\ce{H2+}\) bond order = 0.5, \(\ce{H2-}\) bond order = 0.5, strongest bond is H 2 ;
(b) O 2 bond order = 2, \(\ce{O2^2+}\) bond order = 3; \(\ce{O2^2-}\) bond order = 1, strongest bond is \(\ce{O2^2+}\);
(c) Li 2 bond order = 1, \(\ce{Be2+}\) bond order = 0.5, Be 2 bond order = 0, strongest bond is \(\ce{Li2}\);
(d) F 2 bond order = 1, \(\ce{F2+}\) bond order = 1.5, \(\ce{F2-}\) bond order = 0.5, strongest bond is \(\ce{F2+}\);
For the first ionization energy for an N 2 molecule, what molecular orbital is the electron removed from?
- Answer
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Add texts here. Do not delete this text first.
Compare the atomic and molecular orbital diagrams to identify the member of each of the following pairs that has the highest first ionization energy (the most tightly bound electron) in the gas phase:
(a) H and H 2
(b) N and N 2
(c) O and O 2
(d) C and C 2
(e) B and B 2
Answer
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(a) H 2 ; (b) N 2 ; (c) O; (d) C 2 ; (e) B 2
Which of the period 2 homonuclear diatomic molecules are predicted to be paramagnetic?
- Answer
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Add texts here. Do not delete this text first.
A friend tells you that the 2 s orbital for fluorine starts off at a much lower energy than the 2 s orbital for lithium, so the resulting σ 2 s molecular orbital in F 2 is more stable than in Li 2 . Do you agree?
- Answer
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Yes, fluorine is a smaller atom than Li, so atoms in the 2 s orbital are closer to the nucleus and more stable.
True or false: Boron contains 2 s 2 2 p 1 valence electrons, so only one p orbital is needed to form molecular orbitals.
- Answer
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Add texts here. Do not delete this text first.
What charge would be needed on F 2 to generate an ion with a bond order of 2?
- Answer
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2+
Predict whether the MO diagram for S 2 would show s-p mixing or not.
- Answer
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Add texts here. Do not delete this text first.
Explain why \(\ce{N2^2+}\) is diamagnetic, while \(\ce{O2^4+}\), which has the same number of valence electrons, is paramagnetic.
- Answer
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N 2 has s-p mixing, so the π orbitals are the last filled in \(\ce{N2^2+}\). O 2 does not have s-p mixing, so the σ p orbital fills before the π orbitals.
Using the MO diagrams, predict the bond order for the stronger bond in each pair:
(a) F 2 or \(\ce{F2+}\)
(b) O 2 or \(\ce{O2^2+}\)
Answer
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Add texts here. Do not delete this text first.


3.10: Assignment- Written Communication
You are a regional manager at the Walk-In Closet clothing store and you just received the most recent feedback from a mystery shopper’s in-store experience report. One thing that caught your eye in this report is that the mystery shopper had a hard time identifying a staff member to help them get a changing room. They go on to mention that it was difficult to distinguish between who was a sales associate and who was a customer because there was no standard work uniform. This in not the first time you have read a comment like this. You decide it is time to take action by establishing a dress code for all staff. You are aware there may be some push back from the staff, but if you provide each employee with at least one Walk-In Closet shirt (short or long sleeve) the dress code transition may be easier.
Your task is to write a three-paragraph (minimum) memo addressed to the store managers in your region on the decision to implement an employee dress code program that will be fully implemented by the start of Q3. This memo will discuss the rational, benefits, costs, and time frame involved in executing the new dress code policy. Be sure to address the audience properly, and write to them as a concerned executive. You may also draw from your personal work experience with appropriate examples to support your references.
If you’re not familiar with a Memo style, you can view a sample memo . (Note: Your memo does not need to contain every section included in the sample memo. Just be sure to include the date, recipient, sender, subject, and at least three paragraphs addressing the topic.)
Grading Rubric
| Criteria | Not Evident | Developing | Proficient | Exemplary | Points |
|---|---|---|---|---|---|
| Organization and format |
4 pts
Writing lacks logical organization. It may show some coherence but ideas lack unity. Serious errors and generally is an unorganized format and information. |
6 pts
Writing is coherent and logically organized, using a format suitable for the material presented. Some points may be contextually misplaced and/or stray from the topic. Transitions may be evident but not used throughout the essay. Organization and format used may detract from understanding the material presented. |
8 pts
Writing is coherent and logically organized, using a format suitable for the material presented. Transitions between ideas and paragraphs create coherence. Overall unity of ideas is supported by the format and organization of the material presented. |
10 pts
Writing shows high degree of attention to details and presentation of points. Format used enhances understanding of material presented. Unity clearly leads the reader to the writer’s conclusion and the format and information could be used independently. |
10 pts |
| Content |
4 pts
Some but not all required questions are addressed. Content and/or terminology is not properly used or referenced. Little or no original thought is present in the writing. Concepts presented are merely restated from the source, or ideas presented do not follow the logic and reasoning presented throughout the writing. |
6 pts
All required questions are addressed but may not be addressed with thoughtful consideration and/or may not reflect proper use of content terminology or additional original thought. Additional concepts may not be present and/or may not be properly cited sources. |
8 pts
All required questions are addressed with thoughtful consideration reflecting both proper use of content terminology and additional original thought. Some additional concepts may be presented from other properly cited sources, or originated by the author following logic and reasoning they’ve clearly presented throughout the writing. |
10 pts
All required questions are addressed with thoughtful in-depth consideration reflecting both proper use of content terminology and additional original thought. Additional concepts are clearly presented from properly cited sources, or originated by the author following logic and reasoning they’ve clearly presented throughout the writing. |
10 pts |
| Development – Critical Thinking |
8 pts
Shows some thinking and reasoning but most ideas are underdeveloped, unoriginal, and/or do not address the questions asked. Conclusions drawn may be unsupported, illogical or merely the author’s opinion with no supporting evidence presented. |
12 pts
Content indicates thinking and reasoning applied with original thought on a few ideas, but may repeat information provided and/ or does not address all of the questions asked. The author presents no original ideas, or ideas do not follow clear logic and reasoning. The evidence presented may not support conclusions drawn. |
16 pts
Content indicates original thinking, cohesive conclusions, and developed ideas with sufficient and firm evidence. Clearly addresses all of the questions or requirements asked. The evidence presented supports conclusions drawn. |
20 pts
Content indicates synthesis of ideas, in-depth analysis and evidence beyond the questions or requirements asked. Original thought supports the topic, and is clearly a well-constructed response to the questions asked. The evidence presented makes a compelling case for any conclusions drawn. |
20 pts |
| Grammar, Mechanics, Style |
4 pts
Writing contains many spelling, punctuation, and grammatical errors, making it difficult for the reader to follow ideas clearly. There may be sentence fragments and run-ons. The style of writing, tone, and use of rhetorical devices disrupts the content. Additional information may be presented but in an unsuitable style, detracting from its understanding. |
6 pts
Some spelling, punctuation, and grammatical errors are present, interrupting the reader from following the ideas presented clearly. There may be sentence fragments and run-ons. The style of writing, tone, and use of rhetorical devices may detract from the content. Additional information may be presented, but in a style of writing that does not support understanding of the content. |
8 pts
Writing is free of most spelling, punctuation, and grammatical errors, allowing the reader to follow ideas clearly. There are no sentence fragments and run-ons. The style of writing, tone, and use of rhetorical devices enhance the content. Additional information is presented in a cohesive style that supports understanding of the content. |
10 pts
Writing is free of all spelling, punctuation, and grammatical errors and written in a style that enhances the reader’s ability to follow ideas clearly. There are no sentence fragments and run-ons. The style of writing, tone, and use of rhetorical devices enhance the content. Additional information is presented to encourage and enhance understanding of the content. |
10 pts |
| Total: | 50 pts |
Contributors and Attributions
- Assignment: Written Communication. Provided by : Lumen Learning. License : CC BY: Attribution


15.3: Duties of Agents and Principals
Because they are in a fiduciary relationship, agents and principals owe each other specific duties. While the duties are similar in nature, there are differences based on their roles.
Duties of Agents
Figure 15.2 Duties of Agents
Agents are fiduciaries of principals and so they are required to act with the highest duty of care. In particular, agents owe principals the following duties:
| Duty | Description |
|---|---|
| Account | Agent must keep proper records to account for all principal’s money and property given to agent |
| Care | Agent must act reasonably, in good faith, and avoid negligence at all times |
| Inform | Agent must inform principal of all material facts that affect principal’s interests |
| Loyalty | Agent cannot engage in any dealings that compete or interfere with the principal’s business or interests |
| Obedience | Agent must obey all principal’s instructions within scope of agency unless they are illegal or unethical |
| Protect confidential information | Agent cannot use or disclose principal’s confidential information |
If an agent breaches a duty owed to the principal, the principal has three available remedies:
- The principal may recover damages the breach has caused;
- The principal may receive any profit the agent received as a result of a breach of the duty of loyalty; and
- The principal may rescind a transaction when the duty of loyalty is violated.
Duties of Principals
Principals also owe duties to agents as part of the fiduciary relationship. These duties are:
| Duty | Description |
|---|---|
| Compensation | Principal must pay agent for work performed |
| Honesty | Principals cannot deceive agents about the nature and scope of the work they are to perform |
| Indemnification | Principal must hold agent harmless and free from legal liability for actions properly taken on principal’s behalf |
| Loyalty | Principal cannot engage in any dealings that prevent agent from performing agency tasks |
| Reimbursement | Principal must reimburse agent for money reasonably expended on behalf of principal |
Figure 15.3 Duties of Principals
If a principal breaches a duty owed to the agent, the agent has two available remedies:
- The agent may recover damages the breach has caused; and
- The agent may terminate the agency relationship.


9.6: Basics-Volcanoes
INTRODUCTION
The Pacific Northwest is volcanically active. Nearly every type of volcano exists or has existed in the Pacific Northwest, and every type of volcanic eruption has occurred. The Cascade volcanic arc has been catastrophically active during recent human memory. In the last 10,000 years volcanic eruptions have also occurred in such places as eastern Idaho and central Oregon. In some landscape regions of the Northwest, the entire upper crust is almost entirely volcanic rock.
To understand volcanoes, you have to start with magma, the molten rock that comes up from the interior of the earth to form volcanoes. The composition, gas content, and crystal content of the magma determines the type of eruption that occurs, the kind of volcanic rock that forms, and the type of volcano that forms.
SHIELD VOLCANOES
Lava flow after lava flow of low-viscosity, mafic lava builds up a basaltic shield volcano. Shield volcanoes are the largest type of volcano on earth, as exemplified by Mauna Loa on the Island of Hawaii. Shield volcanoes in the Pacific Northwest include: Medicine Lake Volcano in northern California; Newberry Volcano (Paulina Peak) in Oregon; and Simco Volcano in south Central Washington, on the Yakima Indian Reservation near the town of Goldendale.
COMPOSITE CONES
Eruptions of intermediate lava as andesite flows, explosive eruptions of tephra, and intrusion within earlier flows to form dikes and sills, add up to form composite cones. Composite cones are the characteristic volcanoes of volcanic arcs along subduction zones. Composite cones of the Cascadia volcanic arc in the Pacific Northwest include Lassen Peak and Mt. Shasta in northern California, Mt. McGloughlin, Mt. Mazama (Crater Lake), Mt. Thielsen, the Three Sisters, Mt. Bachelor, Mt. Washington, Mt. Jefferson and Mt. Hood in Oregon, and Mt. Adams, Mt. St. Helens, Mt. Rainier, Glacier Peak, and Mt. Baker in Washington. Most of these volcanoes are over 10,000 feet above sea level in elevation. Along with abundant andesite and tephra, composite cones may also erupt lesser amounts of basalt, dacite and rhyolite. That is why they are called composite cones–they are a composite of many types of volcanic rock.
CINDER CONES
Fountain eruptions of volcanic ash, lapilli, blocks, and bombs, usually of mafic composition, pile up in a cone-shaped form to become a cinder cone. Cinder cones are usually less than 1,000 feet tall. Many composite cones and shield volcanoes have cinder cones on their flanks or close by. Cinder cones are small bumps compared to the much larger shield volcanoes or composite cones.
LAVA DOMES
Lava domes are steep-sided domes formed by the pile-up of viscous, felsic magma. It is not uncommon for a composite cone to erupt explosively, forming a crater, and then to erupt high-viscosity lava into the crater, forming a lava dome. The lava that forms the dome may be from the same magma that erupted explosively but, after venting most of its gas in the explosive eruption, it has lost its explosiveness and erupts as flows.
SPATTER CONES
Spatter cones are small volcanic landforms that from when lava spatters up in a small fountain and piles up in blobs of semi-molten material that accumulate into a solid, roughly cone-shaped form a few feet or a few tens of feet tall. A lava flow coming down the flank of a shield volcano or composite cone may spawn a subsidiary spatter cone by bursting out of a solidified crust.
FLOOD BASALTS
Flood basalts usually originate from fissure eruptions, cracks in the surface of the earth that rapidly disgorge huge volumes of lava. Flood basalts are high-volume, widespread flows of mafic magma that solidify into basalt flows that in some cases cover thousands of square miles. The Columbia River Basalts comprise one of the world’s great flood basalt provinces. Some of the Columbia River basalt flows originated near the border of Idaho, covered much of eastern Washington and north central Oregon, and flowed down through the Columbia River gorge beyond the Cascade Range to cover parts of the Portland area and reach the Pacific Ocean, all in gigantic individual flows.
ASH FLOW TUFFS
Ash flow tuffs are large-volume tuffs that originate from huge, explosive eruptions of felsic magma. They are sometimes referred to as ignimbrites. Besides volcanic ash, ash flow tuffs may contain pieces of pumice, pieces of broken rock that were caught up in the eruption, and crystals that had already solidified in the magma before it erupted. All of these materials become welded together in the solidified ash flow tuff. Some ash flow tuffs cover hundreds or, in rare cases, thousands of square miles. The yellow rock that gives Yellowstone National Park its name is an ash flow tuff. The explosive eruptions that form ash flow tuffs usually create a caldera, as the volcano collapses on itself after venting tephra across the landscape.
PILLOW BASALTS
Pillow basalts form when mafic lava erupts underwater. The lava freezes on the outside against the cold water, but keeps flowing on the inside, bulging out into pillow-like shapes which break off from the main flow. These pillows can accumulate into a large volume of pillow basalts. Pillow basalts serve as an indicator that lava was erupted into a body of water. Much of the world’s oceanic crust consists of basalt, most of which erupted onto the seafloor to form pillow basalts. Pillow basalt can also form when mafic lava erupts on land and flows into a lake or into the ocean. In some places, there are layers of pillow basalt in the Columbia River Basalts, showing that the basalt flowed into lakes, forming pillows as it entered the water.
TEPHRA
Tephra is also known as pyroclastic material—volcanic material that erupted explosively and flew through the air for some distance before landing on the ground. Tephra results from pyroclastic eruptions, which means explosive volcanic eruptions that hurl material into the air. There are several types of pyroclastic material, or tephra:
Volcanic Blocks
Blocks are large (>5 cm) pieces of tephra that were solid during the eruption. They tend to have blocky or jagged shapes.
Volcanic Bombs
Volcanic bombs are large (>5 cm) pieces of tephra that landed while still molten or semi-molten. They tend to have shapes that were streamlined while passing through the air, or else have a sort of splattered shape from hitting the ground while soft.
Lapilli
Lapilli are pieces of tephra between 0.5 and 5 cm across.
Volcanic Ash
Volcanic ash is fine-grained (<0.5 cm) tephra. It mainly consists of fine pieces of volcanic glass, which form by solidification and splintering of small pieces of the magma during the eruption. It may also contain pieces of crystals, from minerals that had already solidified in the magma before it erupted.
REFLECTION QUESTIONS
- What skill does this content help you develop?
- What are the key topics covered in this content?
- How can the content in this section help you demonstrate mastery of a specific skill?
- What questions do you have about this content?
Contributors and Attributions
-
Original content from Kimberly Schulte (Columbia Basin College) and supplemented by Lumen Learning . The content on this page is copyrighted under a Creative Commons Attribution 4.0 International license.


35.4: Hell Hath No Fury Like a Woman Scorned
No part of the story so far stands out to me more than when Unca’s sister, Alluca, makes her move on Winka. There’s no denying the strength of the female characters in The Female American , with Unca Eliza surviving on a desolate island on her own and all. That being said, what the heck is with Alluca? She’s the literal queen of a tribe, yet can’t get over that fact that she isn’t loved by her younger sister’s boyfriend.
Alluca’s strength is in her cultural role, which is probably why Winka didn’t want to be with her. Marrying Alluca would mean that he would have to give her power because they would’ve stayed with the tribe, and women were respected more than they were in European culture. I’m looking at you, salty sea captain who dumps Unca Eliza on an island. Being with Unca allowed him to move back to his plantation and keep the power that his culture gives him, rather than embracing his wife’s cultural lifestyle.
 However menacing these words were, my father was not greatly alarmed, as they were uttered by an unarmed woman” (52). I wanted to scream at him, “dude, she means business don’t smirk,” but he wouldn’t listen me anyway. After she poisons him he seems to sorta get the idea that she was a force to be wrecked with, especially a few years later when she gets her revenge by killing her sister/his wife.
What I’m trying to get at is that Alluca is an amazing female figure, but she’s diluted to the image of a love-crazed girl. It makes her motivations seem simple and one dimensional– like her love for a man was her only driving force for the rest of her life. However that can’t be the only truth. On some level it could be in terms of this book being a love story, but it’s not. So we have to look past that and see that it’s about survival of the fittest (so far), and the only other strong native woman we see is murderous to her own family and dies in that light. We’re meant to see the difference between the sisters Unca and Alluca. Unca is peaceful because of her smooth transition into European culture with her husband. Alluca is murderous and evil because she never converted to Christianity or life on a plantation. She is wild and unkempt; she will lash out on those who find “peace”, and for that she is dangerous.
Winkfield, Unca E, Michelle Burnham, and James Freitas. The Female American; or, The Adventures of Unca Eliza Winkfield . 2014. Print