14.1E: Host Risk Factors
- Recognize the risk factors that increase chance of disease
Most humans are not easily infected. Those who are weak, sick, malnourished, have cancer, or are diabetic have increased susceptibility to chronic or persistent infections. Individuals who have a suppressed immune system or who are on immunosuppressive drugs are particularly susceptible to opportunistic infections.
Risk of infection is a nursing diagnosis which is defined as “the state in which an individual is at risk to be invaded by an opportunistic or pathogenic agent (virus, fungus, bacteria, protozoa, or other parasite) from endogenous or exogenous sources. ” The risk of infection depends on a number of endogenous sources. Skin damage from incision can increase a patient’s risk of infection, as can very young or old age, due to a naive or compromised immune system respectively. Examples of risk factors include decreased immune system resulting from disease, compromised circulation caused by peripheral vascular disease, compromised skin integrity as a result of surgery, or repeated contact with contagious agents.
Risk Reduction
Techniques like hand washing, wearing gowns, and wearing face masks can help prevent infections from being passed between the surgeon and the patient. Frequent hand washing remains the most important defense against the spread of unwanted organisms. Good nutrition is necessary to reduce risk. So is a healthy lifestyle. By avoiding illicit drugs, using a condom, and entering an exercise program one can improve one’s risk factors. Foods should be cooked to recommended temperatures; avoid foods that have been left outside for long. One should not take antibiotics for longer than needed or when they are not needed—long term use of antibiotics leads to resistance and increased the chance of developing opportunistic infections like clostridium difficile colitis. Vaccination is another vital means of preventing infections by encouraging the development of immune resistance in vaccinated hosts.
Key Points
- Risk of infection is a nursing diagnosis; “the state in which an individual is at risk to be invaded by an opportunistic or pathogenic agent (virus, fungus, bacteria, protozoa, or other parasite) from endogenous or exogenous sources” is the diagnostic definition of risk.
- Examples of risk factors includes decreased immune system secondary to disease, compromised circulation secondary to peripheral vascular disease, compromised skin integrity secondary to surgery, or repeated contact with contagious agents.
- Techniques like hand washing, wearing gowns, and wearing face masks can help prevent infections from being passed from the surgeon to the patient or vice versa.
Key Terms
- opportunistic infection : Any infection that causes disease and occurs only when the host’s immune system is impaired.
- colitis : inflammation of the colon.
- vaccination : inoculation with a vaccine in order to protect a particular disease or strain of disease.


4: Further Applications of Trigonometry
In this chapter, we will explore applications of trigonometry that will enable us to solve many different kinds of problems, including finding the height of a tree. We extend topics we introduced in Trigonometric Functions and investigate applications more deeply and meaningfully.
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- 4.1: Non-right Triangles - Law of Sines
- In this section, we will find out how to solve problems involving non-right triangles. The Law of Sines can be used to solve oblique triangles. According to the Law of Sines, the ratio of the measurement of one of the angles to the length of its opposite side equals the other two ratios of angle measure to opposite side. There are three possible cases: ASA, AAS, SSA. Depending on the information given, we can choose the appropriate equation to find the requested solution.
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- 4.2: Non-right Triangles - Law of Cosines
- Unfortunately, while the Law of Sines enables us to address many non-right triangle cases, it does not help us with triangles where the known angle is between two known sides, a SAS (side-angle-side) triangle, or when all three sides are known, but no angles are known, a SSS (side-side-side) triangle. In this section, we will investigate another tool for solving oblique triangles described by these last two cases.
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- 4.3: Polar Coordinates
- When we think about plotting points in the plane, we usually think of rectangular coordinates (x,y) in the Cartesian coordinate plane. However, there are other ways of writing a coordinate pair and other types of grid systems. In this section, we introduce to polar coordinates, which are points labeled (r,θ) and plotted on a polar grid. The polar grid is represented as a series of concentric circles radiating out from the pole, or the origin of the coordinate plane.
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- 4.4: Polar Coordinates - Graphs
- A polar equation describes a relationship between r and θ on a polar grid. It is easier to graph polar equations if we can test the equations for symmetry. There are three symmetry tests that indicate whether the graph of a polar equation will exhibit symmetry. If an equation fails a symmetry test, the graph may or may not exhibit symmetry.
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- 4.5: Polar Form of Complex Numbers
- In this section, we will focus on the mechanics of working with complex numbers: translation of complex numbers from polar form to rectangular form and vice versa, interpretation of complex numbers in the scheme of applications, and application of De Moivre’s Theorem.
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- 4.6: Vectors
- Ground speed refers to the speed of a plane relative to the ground. Airspeed refers to the speed a plane can travel relative to its surrounding air mass. These two quantities are not the same because of the effect of wind. In an earlier section, we used triangles to solve a similar problem involving the movement of boats. Later in this section, we will find the airplane’s ground speed and bearing, while investigating another approach to problems of this type.
Thumbnail: A polar equation describes a curve on the polar grid. The graph of a polar equation can be evaluated for three types of symmetry. Ths image shows one type with a graph is symmetric with respect to the vertical line.
Contributors and Attributions
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Jay Abramson (Arizona State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at https://openstax.org/details/books/precalculus .


2.9: Assignment- Five-Number Summary
In this activity, we will use the Best Actor Oscar winners (1970-2001) to:
- Learn how to use a statistics package to produce the numerical measures, or “descriptive statistics” of a distribution.
- Get some information about the distribution from its five-number summary.
Click here to see the entire dataset.
Choose your statistical package and follow the instructions to compute numerical measures. Note that “n” represents the sample size, which is the number of individuals in the data set.
Instructions
Click on the link corresponding to your statistical package to see instructions for completing the activity, and then answer the questions below.
R | StatCrunch | Minitab | Excel | TI Calculator
Question 1:
Getting information from the output:
a. How many observations are in this data set?
b. What is the mean age of the actors who won the Oscar?
c. What is the five-number summary of the distribution?
Question 2:
Get information from the five-number summary:
a. Half of the actors won the Oscar before what age?
b. What is the range covered by all the actors’ ages?
c. What is the range covered by the middle 50% of the ages?
Contributors and Attributions
- Concepts in Statistics. Provided by : Open Learning Initiative. Located at : http://oli.cmu.edu . License : CC BY: Attribution


14.0: Chapter Scenario
Now it is time to discuss advanced database applications at WorldCorp. As you continue to grow with the company, we will expect you to dive deeper into what is possible with data analysis. Your role will continue to advance as an analyst working with data professionals supporting various teams within WorldCorp.
WorldCorp wants to grow and expand into its independent retail locations to better serve its vast customer base. It still needs to create a database to manage inventory for these new locations. This would involve more complex database design and querying, as well as the use of advanced features in Microsoft Access.
First, we want to determine the data WorldCorp might need to store. We can start by identifying the key elements to track—potential product names, SKU numbers, locations, quantity on hand, and likely reorder points—and designing a table structure to best serve each type of data. For example, you could create a “Products” table with fields for product name, SKU number, description, and unit cost, as well as a “Locations” table with fields for location name and address.
WorldCorp would need a user interface to enter the data for each product and location into their respective tables. We will walk through some advanced steps in Access queries to retrieve specific sets of data from specific tables—for example, a query to find all products with a quantity on hand below the reorder point, or to find all products located in a specific store. You will also learn how to create reports to help keep track of inventory by summarizing and displaying data in a user-friendly format. For example, you could create a report that shows inventory levels by location, or one that shows sales trends by product category.


7: Welcoming and Supporting Families
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Establishing a welcoming environment is an important aspect of fostering family engagement. “A welcoming environment implies that a program has focused efforts on maintaining an atmosphere that is inviting to families and honors their presence” (Constantino 2008, 25). In a welcoming environment, families feel that they belong and seek ways to contribute to the program. They become comfortable with exchanging information with their children’s teachers and open to exploring ways to bring learning activities from the preschool program to home. An essential part of a welcoming environment for families with dual language learners is the program ensuring that they have opportunities to communicate in their home language. Encouraging communication between families with dual language learners who share a home language, hiring staff members (when possible) who are able to communicate in the families’ home language, and providing translations help the families to feel welcome in the preschool setting.


4.5: Subject Matter of Trademarks
After completing this section, you will be able to
- Learn the subject matter of trademarks.
- Analyze characteristics of various forms of trademarks.
As discussed, there are four types of trademarks: trademarks, service marks, certification marks, and collective marks. But what does it mean to say that a trademark may be a “word [or phrase], name, symbol [or design], or device.” The answers may in some cases surprise you.
Words, Phrases, and Names
There is little confusion about what is meant by a trademarkable word , phrase , or name . The only point to remember here is that words, names, and phrases that are simply descriptive of the goods or services with which they are associated do not necessarily qualify for registration as a trademark. xiii They must be distinctive and indicate the origin of a product or service. What is meant by distinctive—and how distinctive they must be—will be discussed in the next section.
Symbols and Devices
Symbols and devices are where things start to get interesting in trademark law. The language of the Lanham Act does not specify what is meant by a “symbol” or a “device” that can be trademarked. The U.S. Supreme Court took careful note of that fact, ruling in 1995 that, “Since human beings might use as a ‘symbol’ or ‘device’ almost anything at all that is capable of carrying meaning, this language, read literally, is not restrictive.” xiv
In the United States, therefore, trademarks can include almost anything that carries distinctive meaning and identifies the origin of products and services. This includes slogans, letters, numbers, logos, three-dimensional designs—even colors, scents, and sounds that indicate the source of a good or service to consumers. xv
A trademarkable symbol can be a number . The number 5, for example, is a trademarked symbol of Chanel No. 5 perfume (No. 73788555). So is the number 31, which is the trademarked symbol of Baskin-Robbins 31 Flavors (No. 72172718).
No trademark can block the use of the numbers 5 or 31 in math. Nor have the courts allowed the trademarking of mere part numbers, xvi model numbers, xvii or grades, xviii because these are not distinctive enough and do not indicate the origin of the goods in question. Regular gas, also known as “87 octane,” also cannot be trademarked because it doesn’t tell you whether that gas comes from Exxon, Shell, or BP.
Yet despite the above, one of the most iconic trademarked numbers is 501. Originally, the number 501 was simply the lot number Levi’s assigned to the famous copper-riveted waist overalls. But over time, 501 acquired meaning in the minds of consumers and came to be very strongly associated with Levi’s brand jeans. How otherwise un-trademarkable symbols (or words and designs) can acquire secondary (trademark) meaning will be discussed in the next section.
As for scents , the fundamental case for trademarking these came about when the USPTO denied Celia Clarke’s request in 1990 for a trademark for scented yarns and threads with a “fresh, floral fragrance reminiscent of Plumeria blossoms.” She appealed, and the Trademark Trial and Appeal Board overruled the examiner, granting her a trademark for the scent.
“[F]ragrance is not an inherent attribute or natural characteristic of applicant’s goods but is rather a feature supplied by applicant,” the board noted. “Moreover, applicant has emphasized this characteristic of her goods in advertising, promoting the scented feature of her goods. Applicant has demonstrated that customers, dealers and distributors of her scented yarns and threads have come to recognize applicant as the source of these goods. . . . In her advertisements and at craft fairs, applicant has promoted her products as having a scented nature. We believe that applicant has presented a prima facie case of distinctiveness of her fragrance mark.” xix
On the other hand, a trademark cannot be granted for any scent that serves a function other than identifying the product’s source. The scent of perfumes and air fresheners, therefore, cannot be registered, nor can the sulfurous smell that serves as a warning for natural gas leaks.
Still, there remains a good deal of uncertainty about when a scent is trademarkable and when it is not. Consider the world-famous Cinnabon smell—that sweet, sugary, cinnamon-infused scent that is absolutely unmistakable (if not also irresistible). But it is not trademarked because even though it is certainly distinctive, it cannot be easily distinguished from the smell of cinnamon buns made by any number of other bakeries.
Sounds can also be trademarked provided they indicate the source of the product or service with which they are associated, and indeed, there are approximately 700 trademarked sounds registered at the USPTO. xx These include Tarzan’s Yell, the THX theme heard at the beginning of a movie, MGM’s roaring lion, America Online’s “You’ve got mail” announcement, the sequence of chimes heard with the display of the NBC logo on TV, and, naturally, the sound of a duck quacking “Aflac!” for the American Family Life Assurance Company.
Designs and Trade Dress
A design , like a logo, can also be trademarked, provided it distinguishes the origin of the product or service from any other source or producer. In these trademarks, the logo must be unique and consist of more than simple stylization.
Bacardi for using a similar stylized “O” on its label for orange-flavored vodka. The court ruled against Geogri, however, because its design consisted merely of a stylized symbol that had not acquired a distinguishing (or secondary) meaning in the minds of consumers that enabled them to identify the producer. xxi
Examples of pure trademarked designs, without any associated words, include Nike’s “Swoosh” and Apple’s famous logo of an apple with a bite taken out of it.
This is why design trademarks often take a “design plus words” approach, as in the trademarked Lacoste logo featuring the word “Lacoste” above the famous green alligator.
Trade dress , on the other hand, refers to the overall appearance of a product or service that indicates its source. Trade dress can include features such as size, shape, color or color combinations, texture, graphics, or even particular sales techniques. The key to claiming trade dress protection is that the attributes must be distinctive. For example, Taco Cabana has trademarked its distinctive and “festive eating atmosphere having interior dining and patio areas decorated with artifacts, bright colors, paintings and murals,” and won an infringement case against a competitor restaurant called Two Pesos. By creating a theme that was similar to Taco Cabana, Two Pesos created confusion in the minds of consumers. xxii
A design trademark may be one part of a product’s trade dress, but it is distinct from trade dress because it only covers the stylization of words, letters, numbers, or of a specific design like the Lacoste green alligator.
Imagine that an Apple competitor opened a retail store with the same colors, lighting, atmosphere, and overall look and feel as the Apple store but sold their own products. The goal would not be to stop the sale of the goods, which are not necessarily infringing any of Apple’s design trademarks or patents, but to stop the competitor from infringing the look and feel of the Apple store. In this case, Apple would file a trade dress suit.
Both design trademarks and trade dress are different from design patents. Although all three cover only nonfunctional designs and appearances, design patents strictly protect only the new and original ornamental design of an article of manufacture, and the actual drawing of a design patent limits what is protected. A design trademark, on the other hand, protects a particular word, name, symbol, or design used in commerce to distinguish a product’s source. And trade dress protects the overall appearance of the product and can include anything that gives a product or service meaning and distinguishes it from those of any other producer.
A design patent might protect the new and original ornamental design of a lamp, for example, so long as that appearance does not affect the lamp’s function. A design trademark would protect the words or symbols used on the lamp that identify it as coming from a particular producer. And trade dress protects the overall “look and feel” of the lamp.
Sometimes both forms of protection can be obtained, providing an extra advantage to the owner of these rights. Examples of products with both design trademarks and design patents include the Dustbuster vacuum cleaner, the Pepsi bottle, and the Honeywell round thermostat.
Footnotes
- xiii United States Patent and Trademark Office. (2012, August 09). Trademark Manual of Examining Procedure § 1202. Retrieved from http://tess2.uspto.gov/bin80/gate.ex...te=nk9n3c.2.14
- xiv Qualitex Co. v. Jacobson Products Co. , 514 U.S. 159, 7 (1995) Retrieved from: http://www.todaysengineer.org/2003/F...514U.S.159.pdf
- xv Henderson, C. International Standards for The Protection of Intellectual Property Rights: Trademarks and Geographical Indications . Retrieved from USPTO website: www.uspto.gov/web/offices/dcom/olia/conf_gipa2007nov2/lebanont
- xvi See Southco, Inc. v. Kanebridge Corp. , 258 F.3d 148, 149 n.2 (3d Cir. 2001).
- xvii See See In re Dana Corp. , 12 USPQ2d 1748 (TTAB 1989).
- xviii See See In re Union Oil Co. , 33 USPQ 43 (C.C.P.A.1937).
- xix In re Clarke, 17 U.S.P.Q.2d 1238 (T.T.A.B. 1990) Retrieved from http://ipmall.info/hosted_resources/...eal_758429.asp
- xx See Constine, J. (2011, December 20). Don’t Let Your Company’s Sound Be Stolen, Trademark it With Trademarkia . Retrieved from http://techcrunch.com/2011/12/20/tra...d-trademarkia/
- xxi Star Industries, Inc. v. Bacardi & Co., LTD. , 412 F.3d 373 (2d Circuit, 2005) Retrieved from http://bulk.resource.org/courts.gov/....04-0831-.html
- xxii 932 F.2d 1113, 1117 (CA5 1991), derived from: http://caselaw.lp.findlaw.com/script...=505&invol=763


1.22: Love and Change and Rational Prediction
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Learning Objectives
- Identify the factors that cause changes in a relationship, the likelihood of their occurrence, and possible ways to overcome or prevent their being problematic.
Watch this video or scan the QR code to see how couples can grow apart.
There are people who change very little in their desires, interests, and abilities as they grow older, many people do change, and some, quite substantially. The problem is how to select a mate that will change in ways that are likely to be beneficial or at least undamaging to the relationship, instead of detrimental to it.
In one Ben Casey episode a shy, serious female rehabilitation physician falls in love with a Don Juan type doctor who had just become handicapped and who has fallen in love with her while he is in her care. But she is hesitant to get involved with him; she told him she was afraid about the future of their relationship. Would their relationship work, particularly when he was no longer so dependent on her, and particularly in light of his past romantic penchant for temporary affairs. His reply was, “Only manufacturers give guarantees.”
To some extent this is true; there are no guarantees. But there are some risks that are not as great as others; there are some risks that are far more reasonable than others. People whose circumstances are likely to change in the future are also people whose characteristics are likely to change in the future. If one partner quits school to support the other’s educational pursuits, it is likely (but not inevitable, of course, if they work at it) for a gap to appear between them in their interests and abilities. What is important or interesting to them now might change. What they think about, how they think about it, and at what level may all change, as might their friends, the types of friends they seek, etc. Likewise when people graduate from high school and go to college, the army, or to a new job. Or when people graduate from college to begin a new job or career. There are certain stages that people go through in their lives that tend to be more likely than others to bring changes in them. And without some sort of conscious and considerable effort, the more likely people are then to grow apart in terms of satisfactions, benefits, or even attraction, from a mate or loved one. Conversely, the less likely it is a couple’s environment will change, the less likely they are to change (drastically) and grow apart from each other. Hence, marriage before much life experience or before the career is permanently underway is riskier in general than marriage afterward.
Reasonably stable environments and circumstances can help relationships remain stable. By reasonably stable environments I do not mean ones that are monotonous, stagnating, and unchanging, but ones that do not make the kinds of drastic changes that would be difficult for almost anyone to cope with and adjust to. Love “on the rebound” is basically love, not whose genuineness, but whose stability, is particularly in question because it occurs under psychological conditions (such as rejection, disappointment, anger, sorrow, sadness, loneliness, depression, lack of confidence in one’s own judgment and/or desirability etc.) that are likely to change, particularly as time and the new love help overcome those conditions. Hence, love on the rebound needs — that is, those conditions need — to be waited out and seen not to be the primary and necessary cause of the love (attraction, joy, and benefit) before long term obligations founded on love — such as living together, marrying, combining property and other financial assets, or parenting — are incurred.
It seems to me there are ways to reduce the risk of growing apart even when one or both partners are going through, or are likely to go through, circumstances that tend to provoke change. First, I think there are general sorts of traits which tend to change less than more specific ones. For example, if one is interested in intellectual pursuits, one may pursue different, specific intellectual interests such as chess, computer programming, music theory, anthropology, or the geometry of Rubik’s cubes. The particular interests may change but the general interest in intellectual pursuits may remain. Periodically, of course, we hear stories about people who give up baseball careers to become geophysicists or who give up teaching philosophy to become non-reading surfers. But I suspect these more drastic kinds of changes are rather rare and certainly less likely than the less drastic kind of changes of specific interests in the same kind of areas. The person who is interested then in intellectual pursuits is more likely to be able to introduce particular new ones to a loved one who is, in general, also interested in intellectual pursuits than to one who is not generally intellectually motivated. Similarly with regard to athletic couples where one partner becomes interested in a new particular sport or training program. Hence, it seems to me that the risk of growing apart is somewhat lessened when both partners have general characteristics or general areas of interest that satisfy and are good for each other, rather than just specific or narrow interests. For example, one plays tennis because he or she likes anything athletic and the other plays tennis because it is the only sport or athletic activity he or she likes. If the latter becomes tired of tennis or has to give it up, there may not be any other sport they can happily play together, and that might be an important gap in their relationship.
Further, I would think it would be a great help if both are good teachers or inciters of enthusiasm about their new interests for each other and if both are willing to learn about the others’ new interests. This does not mean that one needs to learn how to play chess, necessarily, but that one may take delight in learning enough about chess to find out there are puzzle books, anecdote books, etc. to get from the library or a bookstore to give further pleasure to the one who has learned how to play even if the two of you do not play together. Or the second may ask questions of the first to show a certain interest, if not mastery, of the game. If, of the two sports enthusiasts, one learns to snow ski, he or she may be able to teach the other in a very accessible and fun way so that soon the other can be able to ski well enough so that they can do it together. Or, also in terms of sports, one may take up golf and the other tennis — but they can join the same club that offers both, meet each other’s’ friends, share in conversation about each other’s experiences, and be able to understand and appreciate what their different but similar experiences (such as coming from behind to win under pressure or the challenge of facing a much more skilled opponent) have in common and mean to each other. One can learn about oneself in playing a sport, and a golfer and tennis player who are interested in each other as people might be able to share that it felt the same to choke a crucial serve as to choke a crucial putt; and one might be able to teach the other how he or she has been able to overcome choking like that.
Something like this is also true of school or different jobs. With enthusiastic and interesting communication, one can learn a great deal about how and why the new experiences or courses are important and exciting to the other person and can learn and grow along with them. But it requires one who is able to tell interestingly about the experiences and their effects, and another who is able to listen with interest and enthusiasm.
Risk of “growing apart” can also be reduced when it is not so much general or all particular interests that help each enjoy the other, but certain particularly psychologically important interests that are not likely to change, regardless of which particular other areas do change. It is conceivable for two people to marry who have very few common areas of enjoyment and benefit but who treat each other well and kindly and who spend enough time and space together doing what they particularly like to do together that the things they do apart do not impede or basically influence the relationship. Perhaps both have separate careers, both like different people with whom they are able to sufficiently discuss areas that are of no interest to their mates, and both have enough time to devote to the things they alone are interested in, but they are quite comfortable with each other when together and have enough in the relationship that the changes in areas outside the relationship do not affect how they treat or satisfy each other. Each may expect the other to change and mature along with her/himself, but not in the necessarily the same way or the same areas. Each might respect, like, encourage, and strengthen the other enough, and they might have sufficient joy and good together in especially important areas that they can share their lives and truly satisfy (not just apparently or shallowly) benefit each other without being passionately or deeply involved with all or many of each others’ particular, but less meaningful, interests.
Key Takeaways
- There are variables that can stress or bring harm to a love relationship over time, and some are more predictable and perhaps more avoidable than others.
Key Terms
- Reasonably stable environments and circumstances can help relationships remain stable. Reasonably stable environments do not mean ones that are monotonous, stagnating, and unchanging, but instead, refer to environments without drastic changes that would be difficult for almost anyone to cope with and adjust to.
Review Questions
- Question : What are some factors which can jeopardize the stability of a relationship which has been functioning well?
- Question : How can the risk of “growing apart” be reduced?


4.4: Chemical Equations and Stoichiometry
Make sure you thoroughly understand the following essential ideas
- Given the formulas of reactants and products, write a balanced chemical equation for the reaction.
- Given the relative solubilities, write a balanced net ionic equation for a reaction between aqueous solutions of two ionic compounds.
- Write appropriate chemical conversion factors to calculate the masses of all components of a chemical reaction when the mass of any single component is specified in any system of units. and find the masses of all components present when the reaction is complete.
- Describe the manner in which the concept of limiting reactant relates to combustion and human exercise.
A chemical equation expresses the net change in composition associated with a chemical reaction by showing the number of moles of reactants and products. But because each component has its own molar mass, equations also implicitly define the way in which the masses of products and reactants are related. In this unit we will concentrate on understanding and making use of these mass relations.
In a chemical reaction , one or more reactants are transformed into products :
reactants → products
The purpose of a chemical equation is to express this relation in terms of the formulas of the actual reactants and products that define a particular chemical change. For example, the reaction of mercury with oxygen to produce mercuric oxide would be expressed by the equation
Hg + O 2 → HgO 2
Sometimes, for convenience, it is desirable to indicate the physical state (gas, liquid or solid) of one or more of the species by appropriate abbreviations:
Hg(l) + O 2 (g) → HgO 2 (s)
C(graphite) + O 2 (g) → CO 2 (g)
C(diamond) + O 2 (g) → CO 2 (g)
However, this is always optional.
How to read and write chemical equations
A chemical equation is a statement of a fact: it expresses the net change that occurs as the result of a chemical reaction. In doing so, is must be consistent with the law of conservation of mass :
In the context of an ordinary chemical reaction, conservation of mass means that atoms are neither created nor destroyed. This requirement is easily met by making sure that there are equal numbers of all atoms on both sides of the equation.
When we balance an equation, we simply make it consistent with the observed fact that individual atoms are conserved in chemical changes. There is no set “recipe’’ for balancing ordinary chemical equations; it is best to begin by carefully studying selected examples such as those given below.
Write a balanced equation for the combustion of propane C 3 H 8 in oxygen O 2 . The products are carbon dioxide CO 2 and water H 2 O.
Solution
Begin by writing the unbalanced equation
\[C_3H_8 + O_2 → CO_2 + H_2O \nonumber\]
It is usually best to begin by balancing compounds containing the least abundant element, so we first balance the equation for carbon:
C 3 H 8 + O 2 → 3 CO 2 + H 2 O
In balancing the oxygen, we see that there is no way that an even number of O 2 molecules on the left can yield the uneven number of O atoms shown on the right. Don't worry about this now— just use the appropriate fractional coefficient:
C 3 H 8 + 3 ½ O 2 → 3 CO 2 + H 2 O
Finally, we balance the hydrogens by adding more waters on the right:
C 3 H 8 + 7/2 O 2 → 3 CO 2 + 4 H 2 O
Ah, but now the oxygens are off again — fixing this also allows us to get rid of the fraction on the left side:
C 3 H 8 + 5 O 2 → 3 CO 2 + 4 H 2 O
It often happens, however, that we do end up with a fractional coefficient, as in this variant of the above example.
Write a balanced equation for the combustion of ethane C 2 H 6 in oxygen O 2 . The products are carbon dioxide CO 2 and water H 2 O.
Solution
Begin by writing the unbalanced equation
C 2 H 6 + O 2 → CO 2 + H 2 O
...then balance the carbon:
C 2 H 6 + O 2 → 2 CO 2 + H 2 O
Let's balance the hydrogen next:
C 2 H 6 + O 2 → 2 CO 2 + 3 H 2 O
...but now we need a non-integral number of dioxygen molecules on the left:
C 2 H 6 + 7/2 O 2 → 2 CO 2 + 3 H 2 O
My preference is to simply leave it in this form; there is nothing wrong with 7/2 = 3 ½ moles of O 2 , and little to be gained by multiplying every term by two— not unless your teacher is a real stickler for doing it "by the book", in which case you had better write
2 C 2 H 6 + 7 O 2 → 4 CO 2 + 6 H 2 O
Net Ionic Equations
Ionic compounds are usually dissociated in aqueous solution; thus if we combine solutions of silver nitrate AgNO 3 and sodium chloride NaCl we are really combining four different species: the cations (positive ions) Ag + and Na + and the anions (negative ions) NO 3 – and Cl – . It happens that when the ions Ag + and Cl – are brought together, they will combine to form an insoluble precipitate of silver chloride. The net equation for this reaction is
\[Ag^+_{(aq)} + Cl^–_{(aq)} → AgCl_{(s)}\]
Note that
- the ions NO 3 – and Cl – are not directly involved in this reaction; the equation expresses only the net change , which is the removal of the silver and chloride ions from the solution to form an insoluble solid.
- the symbol ( aq ) signifies that the ions are in aqueous solution, and thus are hydrated , or attached to water molecules.
- the symbol ( s ) indicates that the substance AgCl exists as a solid. When a solid is formed in a reaction that takes place in solution, it is known as a precipitate . The formation of a precipitate is often indicated by underscoring.
From the above example involving silver chloride, it is clear that a meaningful net ionic equation can be written only if two ions combine to form an insoluble compound. To make this determination, it helps to know the solubility rules — which all students of chemistry were at one time required to memorize, but are nowadays usually obtained from tables such as the one shown below.
| Anion (negative ion) | Cation (positive ion) | Soluble? |
|---|---|---|
| any anion | alkali metal ions (Li + , Na + , K + , etc.) |
yes
|
| nitrate, NO 3 – | any cation |
yes
|
| acetate, CH 3 COO – | any cation except Ag + |
yes
|
| halide ions Cl – , Br – , or I – | Ag + , Pb 2 + , Hg 2 2 + , Cu 2 + |
no
|
| halide ions Cl – , Br – , or I – | any other cation |
yes
|
| sulfate, SO 4 2– | Ca 2 + , Sr 2 + , Ba 2 + , Ag + , Pb 2 + |
no
|
| sulfate, SO 4 2– | any other cation |
yes
|
| sulfide, S 2 – | alkali metal ions or NH 4 + |
yes
|
| sulfide, S 2 – | Be 2 + , Mg 2 + , Ca 2 + , Sr 2 + , Ba 2 + , Ra 2 + |
yes
|
| sulfide, S 2 – | any other cation |
no
|
| hydroxide, OH – | alkali metal ions or NH 4 + |
yes
|
| hydroxide, OH – | Sr 2 + , Ba 2 + , Ra 2 + |
slightly
|
| hydroxide, OH – | any other cation |
no
|
| phosphate, PO 4 3– , carbonate CO 3 2– | alkali metal ions or NH 4 + |
yes
|
| phosphate, PO 4 3– , carbonate CO 3 2– | any other cation |
no
|
Write net ionic equations for what happens when aqueous solutions of the following salts are combined:
- PbCl 2 + K 2 SO 4
- K 2 CO 3 + Sr(NO 3 ) 2
- AlCl 3 + CaSO 4
- Na 3 PO 4 + CaCl 2
Use the solubility rules table(above) to find the insoluble combinations:
- Pb 2 + ( aq ) + SO 4 2– ( aq ) → PbSO 4 ( s )
- Sr 2 + ( aq ) + CO 3 2– ( aq ) → SrCO 3 ( s )
- no net reaction
- 3 Ca 2 + ( aq ) + 2 PO 4 3– ( aq ) → 3 Ca 3 (PO 4 ) 2 ( s )
Note the need to balance the electric charges
Mass Relations in Chemical Equations
A balanced chemical equation expresses the relative number of moles of each component (product or reactant), but because each formula in the equation implies a definite mass of the substance (its molar mass), the equation also implies that certain weight relations exist between the components. For example, the equation describing the combustion of carbon monoxide to carbon dioxide
\[2 CO + O_2 → 2 CO_2\]
implies the following relations:
The relative masses shown in the bottom line establish the stoichiometry of the reaction, that is, the relations between the masses of the various components. Since these masses vary in direct proportion to one another, we can define what amounts to a conversion factor (sometimes referred to as a chemical factor ) that relates the mass of any one component to that of any other component.
Evaluate the chemical factor and the conversion factor that relates the mass of carbon dioxide to that of the CO consumed in the reaction.
Solution
From the above box, the mass ratio of CO 2 to CO in this reaction is 88/56 = 1.57 ; this is the chemical factor for the conversion of CO into CO 2 . The conversion factor is just 1.57/1 with the mass units explicitly stated:
\[\dfrac{1.57\; g\; CO_2}{ 1\; g\; CO} = 1\]
- How many tons of CO 2 can be obtained from the combustion of 10 tons of CO?
- How many kg of CO must be burnt to produce 20 kg of CO 2 ?
Solutions
- (1.57 T CO 2 / 1 T CO) × (10 T CO) = 15.7 T CO 2
- Notice the answer to this one must refer to carbon monoxide, not CO 2 , so we write the conversion factor in reverse:
(1 kg CO / 1.57 kg CO 2 ) × (20 kg CO 2 ) = (20/1.57)g CO = 12.7 kg CO .
Is this answer reasonable? Yes, because the mass of CO must always be smaller than that of CO 2 in this reaction.
More mass-mass problems
Don't expect to pass Chemistry unless you can handle problems such as the ones below; they come up frequently in all kinds of contexts.
The ore FeS 2 can be converted into the important industrial chemical sulfuric acid H 2 SO 4 by a series of processes. Assuming that the conversion is complete, how many liters of sulfuric acid (density 1.86 kg L –1 ) can be made from 50 kg of ore?
Solution
As with most problems, this breaks down into several simpler ones. We begin by working out the stoichiometry on the assumption that all the sulfur in the or ends up as H 2 SO 4 , allowing us to write
FeS 2 → 2 H 2 SO 4
is balanced in respect to the two components of interest, and this is all we need here. The molar masses of the two components are 120.0 and 98 g mol –1 , respectively, so the equation can be interpreted in terms of masses as[120 mass units] FeS 2 → [2 × 98 mass units] H 2 SO 4
Thus 50 kg of ore will yield (50 kg) × (196/120) = 81.7 kg of product.
[
Check
: is this answer reasonable? Yes, because the factor (196/120) is close to (200/120) = 5/3, so the mass of product should be slightly smaller than twice the mass of ore consumed.]
From the density information we find that the volume of liquid H 2 SO 4 is
(81.7 kg) ÷ (1.86 kg L –1 ) = 43.9 L
[ Check : is this answer reasonable? Yes, because density tells us that the number of liters of acid will be slightly greater than half of its weight.]
Barium chloride forms a crystalline hydrate, BaCl 2 ·xH 2 O, in which x molecules of water are incorporated into the crystalline solid for every unit of BaCl 2 . This water can be driven off by heat; if 1.10 g of the hydrated salt is heated and reweighed several times until no further loss of weight (i.e., loss of water) occurs, the final weight of the sample is 0.937 g. What is the value of x in the formula of the hydrate?
Solution
The first step is to find the number of moles of BaCl 2 (molecular weight 208.2) from the mass of the dehydrated sample.
(0.937 g) / (208.2 g mol –1 ) = 0.00450 mol
Now find the moles of H 2 O (molecular weight 18) lost when the sample was dried:
(1.10 – .937)g / (18 g mol –1 ) = .00905 mol
Allowing for a reasonable amount of measurement error, it is apparent that the mole ratio of BaCl 2 :H2O = 1:2. The formula of the hydrate is BaCl 2 ·2H 2 O .
Limiting Reactants
Most chemical reactions that take place in the real world begin with more or less arbitrary amounts of the various reactants; we usually have to make a special effort if we want to ensure that stoichiometric amounts of the reactants are combined. This means that one or more reactant will usually be present in excess; there will be more present than can react, and some will remain after the reaction is over. At the same time, one reactant will be completely used up; we call this the limiting reactant because the amount of this substance present will control, or limit, the quantities of the other reactants that are consumed as well as the amounts of products produced.
Limiting reactant problems are handled in the same way as ordinary stoichiometry problems with one additional preliminary step: you must first determine which of the reactants is limiting— that is, which one will be completely used up. To start you off, consider the following very simple example
For the hypothetical reaction 3 A + 4 B → [products] , determine which reactant will be completely consumed when we combine
- equimolar quantities of A and B;
- 0.57 mol of A and 0.68 mol of B.
Solution
a) Simple inspection of the equation shows clearly that more moles of B are required, so this component will be consumed (and is thus the limiting reactant), leaving behind ¾ as many moles of A.
b)
How many moles of B will react with .57 mol of A? The answer will be
(4/3 × 0.57 mol). If this comes to less than 0.68 mol, then B will be the limiting reactant, and you must continue the problem on the basis of the amount of B present. If the limiting reactant is A, then all 0.57 mol of A will react, leaving some of the B in excess. Work it out!
Sulfur and copper, when heated together, react to form copper(I) sulfide, Cu 2 S. How many grams of Cu 2 S can be made from 10 g of sulfur and 15 g of copper?
Solution
From the atomic weights of Cu (63.55) and S (32.06) we can interpret the he reaction 2 Cu + S → Cu 2 S as
[2 × 63.55 = 127.1 mass units]
Cu
+ [32.06 mass units] S
→ [159.2 mass units]
Cu
2
S
Thus 10 g of S will require
(10 g S) × (127.1 g Cu)/(32.06 g S) = 39.6 g Cu
...which is a lot more than what is available, so copper is the limiting reactant here.
[Check: is this answer reasonable? Yes, because the chemical factor (127/32) works out to about 4, indicating that sulfur reacts with about four times its weight of copper.]
The mass of copper sulfide formed will be determined by the mass of copper available:
(15 g Cu) × (159.2 g Cu 2 S) / (127.1 g Cu) = 18.8 g Cu 2 S
[Check: is this answer reasonable? Yes, because the chemical factor (159.2/127.1) is just a bit greater than unity, indicating that the mass of the product will slightly exceed that of the copper consumed.]
The concept of limiting reactants touches us all in our everyday lives — and as we will show in the second example below, even in the maintenance of life itself!
Air-to-fuel ratios in combustion
Combustion is an exothermic process in which a fuel is combined with oxygen; complete combustion of a hydrocarbon fuel such as methane or gasoline yields carbon dioxide and water:
CH 4 + 2 O 2 → CO 2 + 2 H 2 O (g)
Calculate the mass ratio of CH 4 to O 2 required for complete combustion.
Solution
This is just the ratio of the molar mass of CH 4 (16 g) to that of two moles of dioxygen (2 x 32 g)
Thus (64 g) / (16 g) = 4/1 = 4.0 .
Incomplete combustion is generally undesirable because it wastes fuel, produces less heat, and releases pollutants such as carbon soot. Energy-producing combustion processes should always operate in fuel-limited mode.
In ordinary combustion processes, the source of oxygen is air. Because only about 20 percent of the molecules in dry air consist of O 2 , the volume of air that must be supplied is five times greater than what would be required for pure O 2 . Calculation of the air-to-fuel mass ratio ("A/F ratio") employed by combustion engineers is complicated by the differing molar masses of dioxygen and air. For methane combustion, the A/F ratio works out to about 17.2
A/F ratios which exceed the stoichiometric values are said to be lean , while those in which air becomes the limiting component are characterized as rich . In order to ensure complete combustion, it is common practice to maintain a slightly lean mixture. The quantities of so-called excess air commonly admitted to burners vary from 5-10% for natural gas to up to 100% for certain grades of coal.For internal combustion engines fueled by gasoline (roughly equivalent to C 7 H 14 ), the stoichiometric A/F ratio is 15:1. However, practical considerations necessitate differing ratios at various stages of operation. Typical values vary from a rich ratio for starting or acceleration to slightly lean ratios for ordinary driving. These ratios are set by the carburetor, with additional control by the engine computer and exhaust-line oxygen sensor in modern vehicles, or by a manual choke in earlier ones.
Aerobic and anaerobic respiration
Our bodies require a continual supply of energy in order to maintain neural activity, synthesize proteins and other essential biochemical components, replace cells, and to power muscular action. The "fuel" — the carrier of chemical energy — glucose, a simple sugar which is released as needed from the starch-like polymer glycogen, the form in which the energy we derive from food is stored. Arterial blood carries dissolved glucose along with hemoglobin-bound dioxygen to individual cells which are the sites of glucose "combustion":
\[C_6H_{12}O_6 + 6 O_2 → 6 CO_2 + 6 H_2O\]
The net reaction and the quantity of energy released are the same as if the glucose were burned in the open air, but within the cells the reaction proceeds in a series of tiny steps which capture most of this energy for the body's use, liberating only a small fraction of it as thermal energy (heat). Because this process utilizes oxygen from the air we breath, it is known as aerobic respiration . And as with any efficient combustion process, glucose is the limiting reactant here.
However, there are times when vigorous physical activity causes muscles to consume glucose at a rate that exceeds the capacity of the blood to deliver the required quantity of oxygen. Under these conditions, cellular respiration shifts to an alternative anaerobic mode:
\[C_6H_{12}O_6 → 2 CH_3CH(OH)COOH\]
As you can see from this equation, glucose is only partially broken down (into lactic acid ), and thus only part of its chemical energy is captured by the body. There are numerous health benefits to aerobic exercise including increased ability of the body to maintain an aerobic condition. But if you are into short-distance running (sprinting) or being pursued by a tiger, the reduced efficiency of anaerobic exercise may be a small price to pay.


3.3.10: Critical Thinking Case
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Stereotypes at Pitney Bowes
Many times, we think of stereotypes or discrimination only being an issue when it comes to things like gender, race, or religion. However, at Pitney Bowes Inc., the toughest stereotype to overcome is age.
Brigitte Van Den Houte starts her day in the normal way; however, she has taken a keen focus on persuading employees in their 20s that they have a future at Pitney Bowes.
For almost 100 years, Pitney Bowes, founded in 1920, has been all about commerce. But as the world turned to technology, the definition of what that meant for the traditional postage-meter equipment company had to change as well.
One of the biggest challenges of this ever-changing technological world is how the generations of employees can step aside from their stereotypes and understand one another to better work effectively.
At Pitney Bowes, their proactive approach puts younger colleagues with older colleagues in a mentoring situation. This is not the typical older mentor to younger mentor setup, however. Every few months, Houte arranges for the younger employees to spend the day with a seasoned executive with the plan of sharing experiences and ideas and offering advice. Houte states, “the old way of working no longer works,” and she’s right.
With over one-third of the workforce aging to 50 or older and millennials (young people aged 22–37) being the largest workforce group, it is imperative to put stereotypes aside and learn to work together. One big mistake for a manager would be to focus on the age difference rather than on what skills each person individually can bring to the table.Stereotypes such as “older individuals don’t know about technology” or “millennials are constantly job hopping and feel entitled” are put aside at Pitney Bowes in order to get the job done. With a more proactive approach, the range of variables within each generation can be utilized in the most effective way possible for an organization.
Questions:
- What are other ways that a company can utilize a multigenerational team to their advantage?
- What challenges does a multigenerational team pose for management?
- What should the company and management team consider when attracting new employees of all
- generations?
Sources: Hymowitz, Carol, “The Tricky Task of Managing the New, Multigenerational Workplace,” The Wall Street Journal , August 12, 2018, https://www.wsj.com/articles/the-tri...s&page=1&pos=9 ; Ault, Nicole, “ Don’t Trust Anyone Over 21,” The Wall Street Journal , August 22, 2018, https://www.wsj.com/articles/dont-tr...s&page=1&pos=1 .


Page 6.2: Trigonometry Preview - Circles
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Recall from Geometry that a circle can be determined by fixing a point (called the center) and a positive number (called the radius) as follows.
Circle
A circle with center \((h,k)\) and radius \(r>0\) is the set of all points \((x, y)\) in the plane whose distance to \((h,k)\) is \(r\).
From the picture, we see that a point \((x,y)\) is on the circle if and only if its distance to \((h,k)\) is \(r\). We express this relationship algebraically using the Distance Formula, as
\[r = \sqrt{(x - h)^2 + (y-k)^2} \nonumber\]
By squaring both sides of this equation, we get an equivalent equation (since \(r > 0\)) which gives us the standard equation of a circle.
The Standard Form of a Circle
The standard form of the equation of a circle with center \((h,k)\) and radius \(r >0\) is
\[(x-h)^2 + (y-k)^2 = r^2. \nonumber\]
Example \(\PageIndex{1}\)
Write the standard equation of the circle with center (−2,3) and radius 5.
Solution .
Here, \((h,k) = (-2,3)\) and \(r = 5\), so we get
\[\begin{array}{rcl} (x-(-2))^2+(y-3)^2 &= &(5)^2 \\ (x+2)^2+(y-3)^2 & = & 25 \end{array} \nonumber\]
Example \(\PageIndex{2}\)
Graph \((x+2)^2+(y-1)^2 = 4\). Find the center and radius.
Solution
From the standard form of a circle, we have that \(x + 2\) is \(x-h\), so \(h = -2\) and \(y - 1\) is \(y - k\) so \(k = 1\). This tells us that our center is \((-2,1)\). Furthermore, \(r^2 = 4\), so \(r = 2\). Thus we have a circle centered at \((-2,1)\) with a radius of \(2\). Graphing gives us
If we were to expand the equation in the previous example and gather up like terms, instead of the easily recognizable \((x+2)^2 + (y-1)^2 = 4\), we'd be contending with \(x^2 + 4x + y^2 - 2y + 1 = 0.\) If we're given such an equation, we can complete the square to rewrite the equation in standard form for a circle.
Example \(\PageIndex{3}\)
Complete the square to find the center and radius of \(3x^2 - 6x + 3y^2 + 4y -4 = 0\).
Solution
\[ \begin{array}{rclr} 3x^2 - 6x + 3y^2 + 4y -4 & = & 0 & \\ 3x^2 - 6x + 3y^2 + 4y & = & 4 & \mbox{add \(4\) to both sides} \\ 3\left(x^2 - 2x \right) + 3\left(y^2 + \dfrac{4}{3} y\right) & = & 4 & \mbox{factor out leading coefficients} \\ 3\left(x^2 - 2x + \underline{1} \right) + 3\left(y^2 + \dfrac{4}{3} y + \underline{\underline{\dfrac{4}{9}}} \right) & = & 4 + 3\underline{(1)} + 3\underline{\underline{\left(\dfrac{4}{9}\right)}} & \mbox{complete the square in \(x\), \(y\)} \\ 3(x - 1)^2 + 3\left(y + \dfrac{2}{3}\right)^2 & = & \dfrac{25}{3} & \mbox{factor} \\ (x - 1)^2 + \left(y + \dfrac{2}{3}\right)^2 & = & \dfrac{25}{9} & \mbox{divide both sides by \(3\)}\end{array} \nonumber\]
From the standard form of a circle, we identify \(x - 1\) as \(x - h\), so \(h = 1\), and \(y + \frac{2}{3}\) as \(y - k\), so \(k = - \frac{2}{3}\). Hence, the center is \((h,k) = \left(1, -\frac{2}{3}\right)\). Furthermore, we see that \(r^2 = \frac{25}{9}\) so the radius is \(r = \frac{5}{3}\).
It is possible to obtain equations like \((x-3)^2 + (y+1)^2 = 0\) or \((x-3)^2 + (y+1)^2 = -1\), neither of which describes a circle. (Do you see why not?) The reader is encouraged to think about what, if any, points lie on the graphs of these two equations.
Example \(\PageIndex{4}\)
Write the standard equation of the circle which has \((-1,3)\) and \((2,4)\) as the endpoints of a diameter.
Solution
We recall that a diameter of a circle is a line segment containing the center and two points on the circle. Plotting the given data yields
Since the given points are endpoints of a diameter, we know their midpoint \((h, k)\) is the center of the circle. Equation \ref{midpointformula} gives us
\[ \begin{array}{rcl} (h,k) & = & \left( \dfrac{x_{\mbox{1}} + x_{\mbox{2}}}{2}, \dfrac{y_{\mbox{1}} + y_{\mbox{2}}}{2} \right) \\ & = & \left( \dfrac{-1+2}{2}, \dfrac{3+4}{2} \right) \\ & = & \left( \dfrac{1}{2}, \dfrac{7}{2} \right) \end{array} \nonumber\]
The diameter of the circle is the distance between the given points, so we know that half of the distance is the radius. Thus,
\[ \begin{array}{rcl} r & = & \dfrac{1}{2} \sqrt{\left(x_{\mbox{2}} - x_{\mbox{1}}\right)^2+\left(y_{\mbox{2}}-y_{\mbox{1}}\right)^2} \\ & = & \dfrac{1}{2} \sqrt{(2-(-1))^2+(4-3)^2} \\ & = & \dfrac{1}{2} \sqrt{3^2+1^2} \\ & = &\dfrac{\sqrt{10}}{2} \end{array} \nonumber\]
Finally, since \(\left( \dfrac{\sqrt{10}}{2} \right)^2 = \dfrac{10}{4}\), our answer becomes \(\left(x - \dfrac{1}{2} \right)^2 + \left(y - \dfrac{7}{2} \right)^2 =\dfrac{10}{4}\)
We close this section with a very important circle that you will learn more about in trigonometry: the Unit Circle .
The Unit Circle
The Unit Circle is the circle centered at \((0,0)\) with a radius of \(1\). The standard equation of the Unit Circle is \(x^2 + y^2 = 1.\)
Example \(\PageIndex{5}\)
Find the points on the unit circle with \(y\)-coordinate \(\dfrac{\sqrt{3}}{2}\).
Solution
We replace \(y\) with \(\dfrac{\sqrt{3}}{2}\) in the equation \(x^2 + y^2 = 1\) to get
\[ \begin{array}{rcl} x^2 + y^2 & = & 1 \\ x^2 + \left(\dfrac{\sqrt{3}}{2}\right)^2 & = & 1 \\ \dfrac{3}{4} + x^2 & = & 1 \\ x^2 & = & \dfrac{1}{4} \\ x & = & \pm \sqrt{\dfrac{1}{4}} \\ x & = & \pm \dfrac{1}{2} \end{array} \nonumber\]
Our final answers are \(\left(\dfrac{1}{2}, \dfrac{\sqrt{3}}{2} \right)\) and \(\left(-\dfrac{1}{2}, \dfrac{\sqrt{3}}{2} \right)\).


7.14: Putting It Together- Consumer Behavior
Applying the Concepts: Finn’s Family Buys a Pet
Do you remember Finn, the newest little consumer who arrived at the beginning of this module? Let’s suppose that Finn’s parents decide they want him to grow up with an animal friend. This gives us a chance to apply what we’ve been discussing about consumer behavior and see what happens as they go through the consumer decision process to buy a pet.
Since finding a pet is definitely a high-involvement decision for them, these are the steps they will go through:
Recognize Needs
The Consumer Perspective: Finn’s parents, Robert and Amanda, know they want a pet. They’re not sure what kind of pet. They’re pretty sure they want it to be cuddly and lovable—something a child can interact with and not get too wet, bitten, or diseased (or maybe just a little). They also want a pet with some longevity, so that Finn can grow up with his animal friend. Although they are busy getting used to a new infant in their lives, Robert and Amanda are both on leave from their jobs for eight weeks, so it could be a good time to get used to a new animal, too. They decide it’s time to get serious about finding a pet.
The Marketer’s Perspective and Tactics: You manage marketing for an animal rescue organization in your local community. Somehow you need to get in front of Finn’s family to let them know about your animals and why they should start their search with you. Fortunately, you’ve been working with Google to get a paid placement for your organization near the top of Google searches for kittens and puppies in your area, so when Robert does his first search, he sees your listing. You also routinely post fliers on information boards around your community, and you’ve been working on your Web site to make sure it is search optimized for people searching for pets in your area.
Search for Information
The Consumer Perspective: Robert has grown skilled at searching the Internet while rocking Finn to sleep at the same time. He and Amanda need to research a few questions:
- What kind of pet should they get: dog, cat, guinea pig, ferret, something else?
- Where should they get the pet: pet shop, breeder, online provide, animal rescue, someplace else?
- How much should they expect to pay for the pet?
- How should they take care of the pet once they get it?
Robert is already leaning strongly toward getting a dog. His family had dogs when he was growing up, and he loves the idea of his son having the same experience. Amanda is on the fence, until they start reading about best pets for kids in parenting articles online, and they start talking to friends. Robert’s family preference for dogs is validated in articles claiming that dogs are good pets for children and that potential problems (allergies, behavior issues) can be minimized by having the dog around children from a young age. As they begin to investigate places to get a dog, Amanda and Robert are disturbed to read about puppy mills and warnings against buying dogs from unscrupulous online sellers. They agree that they should stay local and check out pet shops, breeders, or animal rescue organizations in their area. Animal rescue would probably be the cheapest option, but they want to shop around and see what’s available.
The Marketer’s Perspective and Tactics: One of your organization’s board members is a well-known mommy blogger who feels passionately about pets and kids. At your request, she’s written a few posts over the past several months providing advice for parents who are considering a pet, and recommending animal rescue as the way to go. You’ve cross-posted her pieces on the rescue organization’s Web site blog, and she’s linked to your Web site in her posts. You know from Google Analytics that you’re getting pretty good traffic to your Web site from that link and her posts. The Web site also contains information to educate people about the advantages of adopting rescue animals, reinforcing how rewarding it is to offer these pets a loving home. You know from research that families tend to get interested in pets when they have young children, so you update the Web site with adorable recent-adoption photos showing young families welcoming their new pets. You also know that people have lots of questions when they’re looking for pets, so you prominently feature “Adopting a Pet: What To Expect” on your Web site.
Evaluate Alternatives
The Consumer Perspective: Now that Robert and Amanda know they want a dog, they are honing in on what type of dog and where to get it. They’ve been reading dog owner sites about different breeds, and they’ve been reading Yelp reviews about people’s experiences with the local pet shops, breeders, and rescue organizations. They are keeping an eye on Craigslist to see what shows up there, and they’ve made a couple of visits to see some of the breeds they are considering. Robert is really charmed by a local breeder’s labradoodles, and online communities rave about how good these dogs are with children, but there is a yearlong waitlist for the puppies and they cost upwards of $1,500. Amanda has joined a mothers’ group, and two of the moms have dogs. One has a golden retriever. She bought the dog at a local pet shop and loves him, but she has been surprised by the number of health problems he’s had. The other mom has a friendly terrier mix she got from a local rescue organization, and she was very happy with the experience.
The Marketer’s Perspective and Tactics: You’re trying to do more with word-of-mouth and social media promotion, so you’ve started asking each family that adopts one of your animals to post about their experience on Yelp and Google reviews. You’ve been doing more with Facebook and Instagram, building up followers and posting pictures of some of the sweet rescue animals people can meet and adopt. Since it’s free, you also post regularly in the “Pets” area of Craigslist and you’ve found that is a great way to connect with local area families looking for pets. Craigslist shoppers tend to be good candidates for adopting rescue animals. When people come in to the center, you find out what they are looking for, and you make sure they learn about the advantages of adopting a rescue animal and how simple the process can be. You also get their contact information so you can stay in touch with them electronically and let them know when a new animal arrives that might be a good fit for their family.
Make a Purchase
The Consumer Perspective: Amanda is very moved by their visit to the local animal rescue center. She is impressed with several of the dogs they met, and she loves the idea of adopting an already-house-trained pet, instead of starting from scratch with a puppy. Robert’s heart is still with the labradoodles, but they agree that the yearlong wait and hefty price tag probably aren’t worth it. Although the pet store puppies are adorable, Amanda keeps thinking about her friend’s golden retriever and health problems, which are probably linked to overbreeding. After thinking things over, they decide to return to the rescue center with Finn and meet the dogs there again. This time, one of the dogs is a standout: a smart little Scottish terrier mix named Bonnie who makes Finn’s eyes light up every time she comes near. The choice is made, and the James family is delighted.
The Marketer’s Perspective and Tactics: Once a family comes to the center a second time, you know from experience that they’re hooked. You need to make sure they fall in love with an animal that will be a good fit for their children and living situation. You’ve designed the application process to make sure that it helps you screen people and also match them with the best pets. But it’s also a thoughtful, informative experience for the people who come in, so they can learn about what it takes to be a good pet owner. Once a new pet owner finds “The One,” you snap photos for the happy family bulletin board at the center and ask permission to share the pictures on your Web site and social media. You also invite them to post the picture on social media and share their experience with the center in a Yelp or Foursquare review. A going-home packet includes useful information about caring for their new animal and contact information in case they have questions or concerns.
Post-Purchase Behavior
The Consumer Perspective: The new addition to the James family is everything Amanda and Robert had hoped for. Bonnie is sweet-tempered, playful, gentle with Finn, and smart as a whip. For Robert, Bonnie brings back the joy and companionship he remembers from his childhood pets. Amanda is so delighted that she tells everyone who will listen about their wonderful experience adopting a rescue animal. Next time they are considering a pet, they’ll know exactly where to go.
The Marketer’s Perspective and Tactics: You’ve developed a process for checking in on adoption families after a couple of weeks to make sure things are working out. If they haven’t done so already, you nudge them to write a review about their adoption experience on Yelp or another review site, assuming their experience has been good. If they aren’t doing so well, you try to find out why and suggest some tips and strategies for turning things around. If red flags come up during these conversations, you make a note for one of the center’s volunteers to do a wellness check on the owner and animal, so that the center can intervene and avoid serious problems. Fortunately the follow-up process usually results in happy stories about how much the animals and their new families love each other. And that’s a major reason why you keep doing this job.
Contributors and Attributions
- Putting It Together: Consumer Behavior. Provided by : Lumen Learning. License : CC BY: Attribution
- Cream tabby exotic cat. Authored by : Prskavka. Provided by : Wikimedia Commons. Located at : https://commons.wikimedia.org/wiki/File:Cream_tabby_exotic_cat.jpg .  Authored by : D.C. Atty. Located at : https://www.flickr.com/photos/figgenhoffer/3950586259/ . License : CC BY: Attribution
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2.2: Intermolecular Forces
Skills to Develop
- Describe the types of intermolecular forces possible between atoms or molecules in condensed phases (dispersion forces, dipole-dipole attractions, and hydrogen bonding)
- Identify the types of intermolecular forces experienced by specific molecules based on their structures
- Explain the relation between the intermolecular forces present within a substance and the temperatures associated with changes in its physical state
The differences in the properties of a solid, liquid, or gas reflect the strengths of the attractive forces between the atoms, molecules, or ions that make up each phase. The phase in which a substance exists depends on the relative extents of its intermolecular forces (IMFs) and the kinetic energies (KE) of its molecules. IMFs are the various forces of attraction that may exist between the atoms and molecules of a substance due to electrostatic phenomena, as will be detailed in this module. These forces serve to hold particles close together, whereas the particles’ KE provides the energy required to overcome the attractive forces and thus increase the distance between particles. Figure \(\PageIndex{1}\) illustrates how changes in physical state may be induced by changing the temperature, hence, the average KE, of a given substance.
Forces between Molecules
Under appropriate conditions, the attractions between all gas molecules will cause them to form liquids or solids. This is due to intermolecular forces, not intra molecular forces. Intra molecular forces are those within the molecule that keep the molecule together, for example, the bonds between the atoms. Inter molecular forces are the attractions between molecules, which determine many of the physical properties of a substance. Figure \(\PageIndex{2}\) illustrates these different molecular forces. The strengths of these attractive forces vary widely, though usually the IMFs between small molecules are weak compared to the intramolecular forces that bond atoms together within a molecule. For example, to overcome the IMFs in one mole of liquid HCl and convert it into gaseous HCl requires only about 17 kilojoules. However, to break the covalent bonds between the hydrogen and chlorine atoms in one mole of HCl requires about 25 times more energy—430 kilojoules.
All of the attractive forces between neutral atoms and molecules are also known as van der Waals forces , although they are usually referred to more informally as intermolecular attraction. We will consider the various types of IMFs in the next three sections of this module.
Dipole-Dipole Attractions
Recall from the chapter on chemical bonding and molecular geometry that polar molecules have a partial positive charge on one side and a partial negative charge on the other side of the molecule—a separation of charge called a dipole . Consider a polar molecule such as hydrogen chloride, HCl. In the HCl molecule, the more electronegative Cl atom bears the partial negative charge, whereas the less electronegative H atom bears the partial positive charge. An attractive force between HCl molecules results from the attraction between the positive end of one HCl molecule and the negative end of another. This attractive force is called a dipole-dipole attraction —the electrostatic force between the partially positive end of one polar molecule and the partially negative end of another, as illustrated in Figure \(\PageIndex{3}\).
The effect of a dipole-dipole attraction is apparent when we compare the properties of HCl molecules to nonpolar F 2 molecules. Both HCl and F 2 consist of the same number of atoms and have approximately the same molecular mass. At a temperature of 150 K, molecules of both substances would have the same average KE. However, the dipole-dipole attractions between HCl molecules are sufficient to cause them to “stick together” to form a liquid, whereas the relatively weaker dispersion forces between nonpolar F 2 molecules are not, and so this substance is gaseous at this temperature. The higher normal boiling point of HCl (188 K) compared to F 2 (85 K) is a reflection of the greater strength of dipole-dipole attractions between HCl molecules, compared to the attractions between nonpolar F 2 molecules. We will often use values such as boiling or freezing points, or enthalpies of vaporization or fusion, as indicators of the relative strengths of IMFs of attraction present within different substances.
Dipole-dipole forces give polar molecules stronger intermolecular forces than nonpolar molecules of similar size.
Example \(\PageIndex{1}\): Dipole-Dipole Forces and Their Effects
Predict which will have the higher boiling point: N 2 or CO. Explain your reasoning.
Solution
CO and N 2 are both diatomic molecules with masses of about 28 amu, so they experience similar London dispersion forces. Because CO is a polar molecule, it experiences dipole-dipole attractions. Because N 2 is nonpolar, its molecules cannot exhibit dipole-dipole attractions. The dipole-dipole attractions between CO molecules are comparably stronger than the dispersion forces between nonpolar N 2 molecules, so CO is expected to have the higher boiling point.
Exercise \(\PageIndex{1}\)
Predict which will have the higher boiling point: \(\ce{ICl}\) or \(\ce{Br2}\). Explain your reasoning.
- Answer
-
ICl. ICl and Br 2 have similar masses (~160 amu) and therefore experience similar London dispersion forces. ICl is polar and thus also exhibits dipole-dipole attractions; Br 2 is nonpolar and does not. The relatively stronger dipole-dipole attractions require more energy to overcome, so ICl will have the higher boiling point.
One of the three intermolecular forces is present in all condensed phases, regardless of the nature of the atoms or molecules composing the substance. This attractive force is called the London dispersion force in honor of German-born American physicist Fritz London who first explained it in 1928. This force is often referred to as simply the dispersion force . Because the electrons of an atom or molecule are in constant motion (or, alternatively, the electron’s location is subject to quantum-mechanical variability), at any moment in time, an atom or molecule can develop a temporary, instantaneous dipole if its electrons are distributed asymmetrically. The presence of this dipole can, in turn, distort the electrons of a neighboring atom or molecule, producing an induced dipole . These two rapidly fluctuating, temporary dipoles thus result in a relatively weak electrostatic attraction between the species—a so-called dispersion force like that illustrated in Figure \(\PageIndex{4}\).
Dispersion forces that develop between atoms in different molecules can attract the two molecules to each other. The forces are relatively weak, however, and become significant only when the molecules are very close. Larger and heavier atoms and molecules exhibit stronger dispersion forces than do smaller and lighter atoms and molecules. F 2 and Cl 2 are gases at room temperature (reflecting weaker attractive forces); Br 2 is a liquid, and I 2 is a solid (reflecting stronger attractive forces). Trends in observed melting and boiling points for the halogens clearly demonstrate this effect, as seen in Table \(\PageIndex{1}\).
| Halogen | Molar Mass | Atomic Radius | Melting Point | Boiling Point |
|---|---|---|---|---|
| fluorine, F 2 | 38 g/mol | 72 pm | 53 K | 85 K |
| chlorine, Cl 2 | 71 g/mol | 99 pm | 172 K | 238 K |
| bromine, Br 2 | 160 g/mol | 114 pm | 266 K | 332 K |
| iodine, I 2 | 254 g/mol | 133 pm | 387 K | 457 K |
| astatine, At 2 | 420 g/mol | 150 pm | 575 K | 610 K |
The increase in melting and boiling points with increasing atomic/molecular size may be rationalized by considering how the strength of dispersion forces is affected by the electronic structure of the atoms or molecules in the substance. In a larger atom, the valence electrons are, on average, farther from the nuclei than in a smaller atom. Thus, they are less tightly held and can more easily form the temporary dipoles that produce the attraction. The measure of how easy or difficult it is for another electrostatic charge (for example, a nearby ion or polar molecule) to distort a molecule’s charge distribution (its electron cloud) is known as polarizability . A molecule that has a charge cloud that is easily distorted is said to be very polarizable and will have large dispersion forces; one with a charge cloud that is difficult to distort is not very polarizable and will have small dispersion forces.
Larger and heavier atoms and molecules are more polarizable and therefore exhibit stronger dispersion forces.
Example \(\PageIndex{2}\): London Forces and Their Effects
Order the following compounds of a group 14 element and hydrogen from lowest to highest boiling point: CH 4 , SiH 4 , GeH 4 , and SnH 4 . Explain your reasoning.
Solution
Applying the skills acquired in the chapter on chemical bonding and molecular geometry, all of these compounds are predicted to be nonpolar, so they may experience only dispersion forces: the smaller the molecule, the less polarizable and the weaker the dispersion forces; the larger the molecule, the larger the dispersion forces. The molar masses of CH 4 , SiH 4 , GeH 4 , and SnH 4 are approximately 16 g/mol, 32 g/mol, 77 g/mol, and 123 g/mol, respectively. Therefore, CH 4 is expected to have the lowest boiling point and SnH 4 the highest boiling point. The ordering from lowest to highest boiling point is expected to be
CH 4 < SiH 4 < GeH 4 < SnH 4
A graph of the actual boiling points of these compounds versus the period of the group 14 elements shows this prediction to be correct:
Exercise \(\PageIndex{2}\)
Order the following hydrocarbons from lowest to highest boiling point: C 2 H 6 , C 3 H 8 , and C 4 H 10 .
- Answer
-
All of these compounds are nonpolar and only have London dispersion forces: the larger the molecule, the larger the dispersion forces and the higher the boiling point. The ordering from lowest to highest boiling point is therefore
C 2 H 6 < C 3 H 8 < C 4 H 10 .
The shapes of molecules also affect the magnitudes of the dispersion forces between them. For example, boiling points for the isomers n -pentane, isopentane, and neopentane (shown in Figure \(\PageIndex{5}\)) are 36 °C, 27 °C, and 9.5 °C, respectively. Even though these compounds are composed of molecules with the same chemical formula, C 5 H 12 , the difference in boiling points suggests that dispersion forces in the liquid phase are different, being greatest for n -pentane and least for neopentane. The elongated shape of n -pentane provides a greater surface area available for contact between molecules, resulting in correspondingly stronger dispersion forces. The more compact shape of isopentane offers a smaller surface area available for intermolecular contact and, therefore, weaker dispersion forces. Neopentane molecules are the most compact of the three, offering the least available surface area for intermolecular contact and, hence, the weakest dispersion forces. This behavior is analogous to the connections that may be formed between strips of VELCRO brand fasteners: the greater the area of the strip’s contact, the stronger the connection.
Applications: Geckos and Intermolecular Forces
Geckos have an amazing ability to adhere to most surfaces. They can quickly run up smooth walls and across ceilings that have no toe-holds, and they do this without having suction cups or a sticky substance on their toes. And while a gecko can lift its feet easily as it walks along a surface, if you attempt to pick it up, it sticks to the surface. How are geckos (as well as spiders and some other insects) able to do this? Although this phenomenon has been investigated for hundreds of years, scientists only recently uncovered the details of the process that allows geckos’ feet to behave this way.
Geckos’ toes are covered with hundreds of thousands of tiny hairs known as setae , with each seta, in turn, branching into hundreds of tiny, flat, triangular tips called spatulae . The huge numbers of spatulae on its setae provide a gecko, shown in Figure \(\PageIndex{6}\), with a large total surface area for sticking to a surface. In 2000, Kellar Autumn , who leads a multi-institutional gecko research team, found that geckos adhered equally well to both polar silicon dioxide and nonpolar gallium arsenide. This proved that geckos stick to surfaces because of dispersion forces—weak intermolecular attractions arising from temporary, synchronized charge distributions between adjacent molecules. Although dispersion forces are very weak, the total attraction over millions of spatulae is large enough to support many times the gecko’s weight.
In 2014, two scientists developed a model to explain how geckos can rapidly transition from “sticky” to “non-sticky.” Alex Greaney and Congcong Hu at Oregon State University described how geckos can achieve this by changing the angle between their spatulae and the surface. Geckos’ feet, which are normally nonsticky, become sticky when a small shear force is applied. By curling and uncurling their toes, geckos can alternate between sticking and unsticking from a surface, and thus easily move across it. Further investigations may eventually lead to the development of better adhesives and other applications.
Watch this video to learn more about Kellar Autumn’s research that determined that van der Waals forces are responsible for a gecko’s ability to cling and climb.
Hydrogen Bonding
Nitrosyl fluoride (ONF, molecular mass 49 amu) is a gas at room temperature. Water (H 2 O, molecular mass 18 amu) is a liquid, even though it has a lower molecular mass. We clearly cannot attribute this difference between the two compounds to dispersion forces. Both molecules have about the same shape and ONF is the heavier and larger molecule. It is, therefore, expected to experience more significant dispersion forces. Additionally, we cannot attribute this difference in boiling points to differences in the dipole moments of the molecules. Both molecules are polar and exhibit comparable dipole moments. The large difference between the boiling points is due to a particularly strong dipole-dipole attraction that may occur when a molecule contains a hydrogen atom bonded to a fluorine, oxygen, or nitrogen atom (the three most electronegative elements). The very large difference in electronegativity between the H atom (2.1) and the atom to which it is bonded (4.0 for an F atom, 3.5 for an O atom, or 3.0 for a N atom), combined with the very small size of a H atom and the relatively small sizes of F, O, or N atoms, leads to highly concentrated partial charges with these atoms. Molecules with F-H, O-H, or N-H moieties are very strongly attracted to similar moieties in nearby molecules, a particularly strong type of dipole-dipole attraction called hydrogen bonding . Examples of hydrogen bonds include HF⋯HF, H 2 O⋯HOH, and H 3 N⋯HNH 2 , in which the hydrogen bonds are denoted by dots. Figure \(\PageIndex{7}\) illustrates hydrogen bonding between water molecules.
Despite use of the word “bond,” keep in mind that hydrogen bonds are intermolecular attractive forces, not intramolecular attractive forces (covalent bonds). Hydrogen bonds are much weaker than covalent bonds, only about 5 to 10% as strong, but are generally much stronger than other dipole-dipole attractions and dispersion forces.
Hydrogen bonds have a pronounced effect on the properties of condensed phases (liquids and solids). For example, consider the trends in boiling points for the binary hydrides of group 15 (NH 3 , PH 3 , AsH 3 , and SbH 3 ), group 16 hydrides (H 2 O, H 2 S, H 2 Se, and H 2 Te), and group 17 hydrides (HF, HCl, HBr, and HI). The boiling points of the heaviest three hydrides for each group are plotted in Figure \(\PageIndex{8}\). As we progress down any of these groups, the polarities of the molecules decrease slightly, whereas the sizes of the molecules increase substantially. The effect of increasingly stronger dispersion forces dominates that of increasingly weaker dipole-dipole attractions, and the boiling points are observed to increase steadily. For the group 15, 16, and 17 hydrides, the boiling points for each class of compounds increase with increasing molecular mass for elements in periods 3, 4, and 5. If we use this trend to predict the boiling points for the lightest hydride for each group, we would expect NH 3 to boil at about −120 °C, H 2 O to boil at about −80 °C, and HF to boil at about −110 °C. However, when we measure the boiling points for these compounds, we find that they are dramatically higher than the trends would predict, as shown in Figure \(\PageIndex{8}\). The stark contrast between our naïve predictions and reality provides compelling evidence for the strength of hydrogen bonding.
Example \(\PageIndex{3}\): Effect of Hydrogen Bonding on Boiling Points
Consider the compounds dimethylether (CH 3 OCH 3 ), ethanol (CH 3 CH 2 OH), and propane (CH 3 CH 2 CH 3 ). Their boiling points, not necessarily in order, are −42.1 °C, −24.8 °C, and 78.4 °C. Match each compound with its boiling point. Explain your reasoning.
Solution
The VSEPR-predicted shapes of CH 3 OCH 3 , CH 3 CH 2 OH, and CH 3 CH 2 CH 3 are similar, as are their molar masses (46 g/mol, 46 g/mol, and 44 g/mol, respectively), so they will exhibit similar dispersion forces. Since CH 3 CH 2 CH 3 is nonpolar, it may exhibit only dispersion forces. Because CH 3 OCH 3 is polar, it will also experience dipole-dipole attractions. Finally, CH 3 CH 2 OH has an −OH group, and so it will experience the uniquely strong dipole-dipole attraction known as hydrogen bonding. So the ordering in terms of strength of IMFs, and thus boiling points, is CH 3 CH 2 CH 3 < CH 3 OCH 3 < CH 3 CH 2 OH. The boiling point of propane is −42.1 °C, the boiling point of dimethylether is −24.8 °C, and the boiling point of ethanol is 78.5 °C.
Exercise \(\PageIndex{3}\)
Ethane (CH 3 CH 3 ) has a melting point of −183 °C and a boiling point of −89 °C. Predict the melting and boiling points for methylamine (CH 3 NH 2 ). Explain your reasoning.
- Answer:
-
The melting point and boiling point for methylamine are predicted to be significantly greater than those of ethane. CH 3 CH 3 and CH 3 NH 2 are similar in size and mass, but methylamine possesses an −NH group and therefore may exhibit hydrogen bonding. This greatly increases its IMFs, and therefore its melting and boiling points. It is difficult to predict values, but the known values are a melting point of −93 °C and a boiling point of −6 °C.
Applications: Hydrogen Bonding and DNA
Deoxyribonucleic acid (DNA) is found in every living organism and contains the genetic information that determines the organism’s characteristics, provides the blueprint for making the proteins necessary for life, and serves as a template to pass this information on to the organism’s offspring. A DNA molecule consists of two (anti-)parallel chains of repeating nucleotides, which form its well-known double helical structure, as shown in Figure \(\PageIndex{9}\).
Figure \(\PageIndex{9}\): Two separate DNA molecules form a double-stranded helix in which the molecules are held together via hydrogen bonding. (credit: modification of work by Jerome Walker, Dennis Myts)
Each nucleotide contains a (deoxyribose) sugar bound to a phosphate group on one side, and one of four nitrogenous bases on the other. Two of the bases, cytosine (C) and thymine (T), are single-ringed structures known as pyrimidines. The other two, adenine (A) and guanine (G), are double-ringed structures called purines. These bases form complementary base pairs consisting of one purine and one pyrimidine, with adenine pairing with thymine, and cytosine with guanine. Each base pair is held together by hydrogen bonding. A and T share two hydrogen bonds, C and G share three, and both pairings have a similar shape and structure Figure \(\PageIndex{10}\)
The cumulative effect of millions of hydrogen bonds effectively holds the two strands of DNA together. Importantly, the two strands of DNA can relatively easily “unzip” down the middle since hydrogen bonds are relatively weak compared to the covalent bonds that hold the atoms of the individual DNA molecules together. This allows both strands to function as a template for replication.
Summary
The physical properties of condensed matter (liquids and solids) can be explained in terms of the kinetic molecular theory. In a liquid, intermolecular attractive forces hold the molecules in contact, although they still have sufficient kinetic energy to move past each other. Intermolecular attractive forces, collectively referred to as van der Waals forces, are responsible for the behavior of liquids and solids and are electrostatic in nature. Dipole-dipole attractions result from the electrostatic attraction of the partial negative end of one dipolar molecule for the partial positive end of another. The temporary dipole that results from the motion of the electrons in an atom can induce a dipole in an adjacent atom and give rise to the London dispersion force. London forces increase with increasing molecular size. Hydrogen bonds are a special type of dipole-dipole attraction that results when hydrogen is bonded to one of the three most electronegative elements: F, O, or N.
Glossary
- dipole-dipole attraction
- intermolecular attraction between two permanent dipoles
- dispersion force
- (also, London dispersion force) attraction between two rapidly fluctuating, temporary dipoles; significant only when particles are very close together
- hydrogen bonding
- occurs when exceptionally strong dipoles attract; bonding that exists when hydrogen is bonded to one of the three most electronegative elements: F, O, or N
- induced dipole
- temporary dipole formed when the electrons of an atom or molecule are distorted by the instantaneous dipole of a neighboring atom or molecule
- instantaneous dipole
- temporary dipole that occurs for a brief moment in time when the electrons of an atom or molecule are distributed asymmetrically
- intermolecular force
- noncovalent attractive force between atoms, molecules, and/or ions
- polarizability
- measure of the ability of a charge to distort a molecule’s charge distribution (electron cloud)
- van der Waals force
- attractive or repulsive force between molecules, including dipole-dipole, dipole-induced dipole, and London dispersion forces; does not include forces due to covalent or ionic bonding, or the attraction between ions and molecules
Contributors
-
Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at<EMAIL_ADDRESS>).


1.10: Reproductive System Anatomy
- Identify male and female reproductive system gross anatomical structures.
- Identify male and female reproductive system microscopic structures.
Gross and Microscopic Anatomy
Use local resources to view structures of the reproductive system.
Female Reproductive Structures List
-
Complete Female Reproductive System- Anterior view
- Ovary
- Ovarian ligament
- Oviduct (Fallopian tube)
-
Complete Female Reproductive System- Lateral view
- Ilium
- Piriformis muscle
- Internal obturator muscle
-
Female Pelvis- Organs removed- Anterior view
- Sacrum
-
Female Pelvis- Organs removed- Inferior view
- Labia minora
- Labia majora
- Sacrotuberous ligament
- Sacrospinal/sacrospinous ligament
- Levator ani muscle
-
Excised Female Pelvis Organs- Superior view
- Broad ligament
- Round ligament of the uterus
- Ureters
- Recto-uterine fold
-
Female Pelvic Organs- Sagittal view
- Vagina
- Uterus
- Cervix
-
Female Pelvis- Sagittal view
- Urogenital diaphragm
- External anal sphincter
- Internal anal sphincter
Male Reproductive Structures List
-
Complete Male Reproductive System- Anterior view
-
Penis
- Glans penis
-
Corona
- Prepuce
- Scrotum
- Spermatic cord
- Ureters
-
Penis
-
Complete Male Reproductive System- Sagittal view
- Corpus cavernosum
- Corpus spongiosum
- Bulb of penis
- Fundiform ligament
- Spongy urethra
- Membranous urethra
- Bulbourethral gland
- Prostate gland
- Urogenital diaphragm
- Internal anal sphincter
- External anal sphincter
- Levator ani muscle
- Obturator internus muscle
-
Male Reproductive System- Accessory Organs- Sagittal view
- Prostatic urethra
- Ejaculatory duct
-
Male Reproductive System- Penis and testicle
-
Scrotum
- External membrane
- Tunica dartos
- Fascia spermatica externa
- Cremaster muscle
- Fascia spermatica interna
- Testis
- Epididymis
- Ductus deferens
-
Scrotum
Attributions for chapter 10:
Female Reproductive Structures List by Marissa Sumida /
CC BY 4.0
Male Reproductive Structures List by Marissa Sumida /
CC BY 4.0


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“the medium is the message”
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the notion that each genre of media has its own set of features that suggest certain uses and types of content.
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community radio
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radio stations that are community owned and operated, staffed by groups of professionals and volunteers.
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cosmopolitanism
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worldly knowledge and sophistication, often associated with involvement in global forms of media.
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ethnographic film
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the use of film in ethnographic research, either as a method, a record, or a means of reporting on anthropological fieldwork.
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Faustian bargain
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the idea that a person can engage in evil supernatural activities in order to gain access to worldly desires such as wealth, sex, and/or knowledge.
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imperial gaze
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a set of conventions for how people in imperial or colonizing societies view the people and landscapes of subjugated territories.
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independent media
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forms of print and broadcast media that are privately owned.
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Indigenous media
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the use of media by Indigenous peoples for community identity, cultural representation, and activism.
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male gaze
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a set of conventions for how men look at women.
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mass media
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mechanically reproduced forms of communication targeting large audiences.
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media
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tools for storing and sharing information.
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media ideologies
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sets of ideas about the uses and functions of a particular genre of media.
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public sphere
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a domain of social life in which people represent, learn about, and discuss the important issues of the day.
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sakawa
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magically enhanced Internet fraud, mainly targeting foreigners.
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sociality
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participation in social relations; how people construct and maintain their personal and group relationships.
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soli
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short for
solidarity
; a small sum of money given by news sources to journalists at the end of an assignment in Ghana.
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state media
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forms of print and broadcast media that are financially supported by the state and subject to government control.
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technophilia
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the love of technology; characteristic of societies and eras of increasing technological innovation and its incorporation into everyday life.
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the gaze
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a specific mode of looking at images shaped by the identities of viewer and viewed.
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visual anthropology
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the use of visual media as a method of research or its study as a topic of research.
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voyeuristic
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describes a gaze aimed at people who do not know they are being viewed.


7.1: Mindset and Decision-making
In an earlier chapter we discussed mindset and locus of control. When making decisions, we focus on two aspects of mindset:
- A positive self-empowering mindset
- A negative self-victimizing mindset
Our mindset is impacted by the internal and external factors to be discussed in this chapter. We have to recognize that allowing a negative mindset or external locus of control to impact how we make decisions is our choice, but a positive mindset or internal locus of control will have a positive impact on our decision-making process. Compare this idea to being in the car. You want to be in the driver seat of your life (positive mindset, internal locus of control = self-empowering), or you can choose to sit in the passenger seat and not be in control of where the car is going (negative mindset, external locus of control = self-victimizing). When we allow a negative mindset, we give up control to the following elements:
- Time : delaying the decision is easy until we run out of time and/or options (e.g. “I can’t deal with this right now”);
- Fate : thinking “what will happen, will happen, no matter what I do”
- Others : going along with what someone else decides
- Comfort : choosing the path of least resistance or what is familiar and comfortable
- Emotions : going with how feelings in the moment
When we use a positive self-empowering mindset to make decisions, we use a decision-making process that lets us identify and analyze our options. After the analysis of our options, we then make the decision using one of the approaches listed below:
- Analytical - What option has more pros than cons?
- Intuitive - Which option feels right?
Remember the psychological preferences we discussed earlier in this text when discussing personality typology theories. According to the Myers-Briggs Type Indicator, the Thinking-Feeling (TF) dichotomy is how we make decisions . If we are on the Thinking side of the continuum, we make decisions using logic, and we value fairness and reason. If we are on the Feeling side of the continuum, we make decisions based on personal values and how decisions might affect others, and we value harmony. If we prefer Thinking, we may tend to use the analytical approach to decision-making, and if we prefer Feeling, we may tend to use the intuitive decision-making approach. As with all our preferences, however, we can function on either side of the dichotomy, and we may use different decision-making approaches according to different types of decisions.