8.1: Asteroids
Learning Objectives
By the end of this section, you will be able to:
- Outline the story of the discovery of asteroids and describe their typical orbits
- Describe the composition and classification of the various types of asteroids
- Discuss what was learned from spacecraft missions to several asteroids
The asteroids are mostly found in the broad space between Mars and Jupiter, a region of the solar system called the asteroid belt . Asteroids are too small to be seen without a telescope; the first of them was not discovered until the beginning of the nineteenth century.
Discovery and Orbits of the Asteroids
In the late 1700s, many astronomers were hunting for an additional planet they thought should exist in the gap between the orbits of Mars and Jupiter. The Sicilian astronomer Giovanni Piazzi thought he had found this missing planet in 1801, when he discovered the first asteroid (or as it was later called, “minor planet”) orbiting at 2.8 AU from the Sun. His discovery, which he named Ceres, was quickly followed by the detection of three other little planets in similar orbits.
Clearly, there was not a single missing planet between Mars and Jupiter but rather a whole group of objects, each much smaller than our Moon. (An analogous discovery history has played out in slow motion in the outer solar system. Pluto was discovered beyond Neptune in 1930 and was initially called a planet, but early in the twenty-first century, several other similar objects were found. We now call all of them dwarf planets.)
By 1890, more than 300 of these minor planets or asteroids had been discovered by sharp-eyed observers. In that year, Max Wolfat Heidelberg introduced astronomical photography to the search for asteroids, greatly accelerating the discovery of these dim objects. In the twenty-first century, searchers use computer-driven electronic cameras, another leap in technology. More than half a million asteroids now have well-determined orbits.
Asteroids are given a number (corresponding to the order of discovery) and sometimes also a name. Originally, the names of asteroids were chosen from goddesses in Greek and Roman mythology. After exhausting these and other female names (including, later, those of spouses, friends, flowers, cities, and others), astronomers turned to the names of colleagues (and other people of distinction) whom they wished to honor. For example, asteroids 2410, 4859, and 68448 are named Morrison, Fraknoi, and Sidneywolff, for the three original authors of this textbook.
The largest asteroid is Ceres (numbered 1), with a diameter just less than 1000 kilometers. As we saw, Ceres was considered a planet when it was discovered but later was called an asteroid (the first of many.) Now, it has again been reclassified and is considered one of the dwarf planets, like Pluto (see the chapter on Moons, Rings and Pluto). We still find it convenient, however, to discuss Ceres as the largest of the asteroids. Two other asteroids, Pallas and Vesta, have diameters of about 500 kilometers, and about 15 more are larger than 250 kilometers (see Table \(\PageIndex{1}\)). The number of asteroids increases rapidly with decreasing size; there are about 100 times more objects 10 kilometers across than there are 100 kilometers across. By 2016, nearly a million asteroids have been discovered by astronomers.
The Minor Planet Center is a worldwide repository of data on asteroids. Visit it online to find out about the latest discoveries related to the small bodies in our solar system. (Note that some of the material on this site is technical; it’s best to click on the menu tab for the “public” for information more at the level of this textbook.)
| Table \(\PageIndex{1}\): The Largest Asteroids | |||||
|---|---|---|---|---|---|
| # | Name | Year of Discovery | Orbit’s Semimajor Axis (AU) | Diameter (km) | Compositional Class |
| 1 | Ceres | 1801 | 2.77 | 940 | C (carbonaceous) |
| 2 | Pallas | 1802 | 2.77 | 540 | C (carbonaceous) |
| 3 | Juno | 1804 | 2.67 | 265 | S (stony) |
| 4 | Vesta | 1807 | 2.36 | 510 | basaltic |
| 10 | Hygiea | 1849 | 3.14 | 410 | C (carbonaceous) |
| 16 | Psyche | 1852 | 2.92 | 265 | M (metallic) |
| 31 | Euphrosyne | 1854 | 3.15 | 250 | C (carbonaceous) |
| 52 | Europa | 1858 | 3.10 | 280 | C (carbonaceous) |
| 65 | Cybele | 1861 | 3.43 | 280 | C (carbonaceous) |
| 87 | Sylvia | 1866 | 3.48 | 275 | C (carbonaceous) |
| 451 | Patientia | 1899 | 3.06 | 260 | C (carbonaceous) |
| 511 | Davida | 1903 | 3.16 | 310 | C (carbonaceous) |
| 704 | Interamnia | 1910 | 3.06 | 310 | C (carbonaceous) |
The asteroids all revolve about the Sun in the same direction as the planets, and most of their orbits lie near the plane in which Earth and other planets circle. The majority of asteroids are in the asteroid belt, the region between Mars and Jupiter that contains all asteroids with orbital periods between 3.3 to 6 years (Figure). Although more than 75% of the known asteroids are in the belt, they are not closely spaced (as they are sometimes depicted in science fiction movies). The volume of the belt is actually very large, and the typical spacing between objects (down to 1 kilometer in size) is several million kilometers. (This was fortunate for spacecraft like Galileo, Cassini, Rosetta , and New Horizons, which needed to travel through the asteroid belt without a collision.)
Still, over the long history of our solar system, there have been a good number of collisions among the asteroids themselves. In 1918, the Japanese astronomer Kiyotsugu Hirayama found that some asteroids fall into families , groups with similar orbital characteristics. He hypothesized that each family may have resulted from the breakup of a larger body or, more likely, from the collision of two asteroids. Slight differences in the speeds with which the various fragments left the collision scene account for the small spread in orbits now observed for the different asteroids in a given family. Several dozen such families exist, and observations have shown that individual members of most families have similar compositions, as we would expect if they were fragments of a common parent.
Composition and Classification
Asteroids are as different as black and white. The majority are very dark, with reflectivity of only 3 to 4%, like a lump of coal. However, another large group has a typical reflectivity of 15%. To understand more about these differences and how they are related to chemical composition, astronomers study the spectrum of the light reflected from asteroids for clues about their composition.
The dark asteroids are revealed from spectral studies to be primitive bodies (those that have changed little chemically since the beginning of the solar system) composed of silicates mixed with dark, organic carbon compounds. These are known as C-type asteroids (“C” for carbonaceous). Two of the largest asteroids, Ceres and Pallas, are primitive, as are almost all of the asteroids in the outer part of the belt.
The second most populous group is the S-type asteroids, where “S” stands for a stony or silicate composition. Here, the dark carbon compounds are missing, resulting in higher reflectivity and clearer spectral signatures of silicate minerals. The S-type asteroids are also chemically primitive, but their different composition indicates that they were probably formed in a different location in the solar system from the C-type asteroids.
Asteroids of a third class, much less numerous than those of the first two, are composed primarily of metal and are called M-type asteroids (“M” for metallic). Spectroscopically, the identification of metal is difficult, but for at least the largest M-type asteroid, Psyche, this identification has been confirmed by radar. Since a metal asteroid, like an airplane or ship, is a much better reflector of radar than is a stony object, Psyche appears bright when we aim a radar beam at it.
How did such metal asteroids come to be? We suspect that each came from a parent body large enough for its molten interior to settle out or differentiate, and the heavier metals sank to the center. When this parent body shattered in a later collision, the fragments from the core were rich in metals. There is enough metal in even a 1-kilometer M-type asteroid to supply the world with iron and many other industrial metals for the foreseeable future, if we could bring one safely to Earth.
In addition to the M-type asteroids, a few other asteroids show signs of early heating and differentiation. These have basaltic surfaces like the volcanic plains of the Moon and Mars; the large asteroid Vesta (discussed in a moment) is in this last category.
The different classes of asteroids are found at different distances from the Sun (Figure \(\PageIndex{2}\)). By tracing how asteroid compositions vary with distance from the Sun, we can reconstruct some of the properties of the solar nebula from which they originally formed.
Vesta: A Differentiated Asteroid
Vesta is one of the most interesting of the asteroids. It orbits the Sun with a semi-major axis of 2.4 AU in the inner part of the asteroid belt. Its relatively high reflectivity of almost 30% makes it the brightest asteroid, so bright that it is actually visible to the unaided eye if you know just where to look. But its real claim to fame is that its surface is covered with basalt, indicating that Vesta is a differentiated object that must once have been volcanically active, in spite of its small size (about 500 kilometers in diameter).
Meteorites from Vesta’s surface (Figure \(\PageIndex{3}\)), identified by comparing their spectra with that of Vesta itself, have landed on Earth and are available for direct study in the laboratory. We thus know a great deal about this asteroid. The age of the lava flows from which these meteorites derived has been measured at 4.4 to 4.5 billion years, very soon after the formation of the solar system. This age is consistent with what we might expect for volcanoes on Vesta; whatever process heated such a small object was probably intense and short-lived. In 2016, a meteorite fell in Turkey that could be identified with a particular lava flow as revealed by the orbiting Dawn spacecraft.
Asteroids Up Close
On the way to its 1995 encounter with Jupiter, the Galileo spacecraft was targeted to fly close to two main-belt S-type asteroids called Gaspra and Ida. The Galileo camera revealed both as long and highly irregular (resembling a battered potato), as befits fragments from a catastrophic collision (Figure \(\PageIndex{4}\)).
The detailed images allowed us to count the craters on Gaspra and Ida, and to estimate the length of time their surfaces have been exposed to collisions. The Galileo scientists concluded that these asteroids are only about 200 million years old (that is, the collisions that formed them took place about 200 million years ago). Calculations suggest that an asteroid the size of Gaspra or Ida can expect another catastrophic collision sometime in the next billion years, at which time it will be disrupted to form another generation of still-smaller fragments.
The greatest surprise of the Galileo flyby of Ida was the discovery of a moon (which was then named Dactyl), in orbit about the asteroid (Figure \(\PageIndex{5}\)). Although only 1.5 kilometers in diameter, smaller than many college campuses, Dactyl provides scientists with something otherwise beyond their reach—a measurement of the mass and density of Ida using Kepler’s laws. The moon’s distance of about 100 kilometers and its orbital period of about 24 hours indicate that Ida has a density of approximately 2.5 g/cm 3 , which matches the density of primitive rocks. Subsequently, both large visible-light telescopes and high-powered planetary radar have discovered many other asteroid moons, so that we are now able to accumulate valuable data on asteroid masses and densities.
By the way, Phobos and Deimos, the two small moons of Mars, are probably captured asteroids (Figure \(\PageIndex{6}\)). They were first studied at close range by the Viking orbiters in 1977 and later by Mars Global Surveyor . Both are irregular, somewhat elongated, and heavily created, resembling other smaller asteroids. Their largest dimensions are about 26 kilometers and 16 kilometers, respectively. The small outer moons of Jupiter and Saturn were probably also captured from passing asteroids, perhaps early in the history of the solar system.
Beginning in the 1990s, spacecraft have provided close looks at several more asteroids. The Near Earth Asteroid Rendezvous (NEAR) spacecraft went into orbit around the S-type asteroid Eros, becoming a temporary moon of this asteroid. On its way to Eros, the NEAR spacecraft was renamed after planetary geologist Eugene Shoemaker, a pioneer in our understanding of craters and impacts.
For a year, the NEAR-Shoemaker spacecraft orbited the little asteroid at various altitudes, measuring its surface and interior composition as well as mapping Eros from all sides (Figure \(\PageIndex{7}\)). The data showed that Eros is made of some of the most chemically primitive materials in the solar system. Several other asteroids have been revealed as made of loosely bound rubble throughout, but not Eros. Its uniform density (about the same as that of Earth’s crust) and extensive global-scale grooves and ridges show that it is a cracked but solid rock.
Eros has a good deal of loose surface material that appears to have slid down toward lower elevations. In some places, the surface rubble layer is 100 meters deep. The top of loose soil is dotted with scattered, half-buried boulders. There are so many of these boulders that they are more numerous than the craters. Of course, with the gravity so low on this small world, a visiting astronaut would find loose boulders rolling toward her pretty slowly and could easily leap high enough to avoid being hit by one. Although the NEAR-Shoemaker spacecraft was not constructed as a lander, at the end of its orbital mission in 2000, it was allowed to fall gently to the surface, where it continued its chemical analysis for another week.
In 2003, Japan’s Hayabusa 1 mission not only visited a small asteroid but also brought back samples to study in laboratories on Earth. The target S-type asteroid, Itokawa (shown in Figure \(\PageIndex{8}\)), is much smaller than Eros, only about 500 meters long. This asteroid is elongated and appears to be the result of the collision of two separate asteroids long ago. There are almost no impact craters, but an abundance of boulders (like a pile of rubble) on the surface.
The Hayabusa spacecraft was designed not to land, but to touch the surface just long enough to collect a small sample. This tricky maneuver failed on its first try, with the spacecraft briefly toppling over on its side. Eventually, the controllers were successful in picking up a few grains of surface material and transferring them into the return capsule. The 2010 reentry into Earth’s atmosphere over Australia was spectacular (Figure \(\PageIndex{9}\)), with a fiery breakup of the spacecraft, while a small return capsule successfully parachuted to the surface. Months of careful extraction and study of more than a thousand tiny dust particles confirmed that the surface of Itokawa had a composition similar to a well-known class of primitive meteorites. We estimate that the dust grains Hayabusa picked up had been exposed on the surface of the asteroid for about 8 million years.
At the end of 2018, two spacecraft rendezvoused with Near Earth Asteroids (see Asteroids and Planetary Defense) and prepared to land and collect samples for return to Earth. The Japanese Hayabusa2 spacecraft reached Ryugu, and the NASA OSIRIS-REx targeted Bennu. Both of these asteroids, each less than 1 km in diameter, are of the dark, carbonaceous class. Because such objects are water-rich, they are of special interest as possible future space resources. Both asteroids appear to be “rubble piles,” or loosely bound agglomerations of small fragments.
The most ambitious asteroid space mission (called Dawn) has visited the two largest main belt asteroids, Ceres and Vesta, orbiting each for about a year (Figure \(\PageIndex{10}\)). Their large sizes (diameters of about 1000 and 500 kilometers, respectively) make them appropriate for comparison with the planets and large moons. Both turned out to be heavily cratered, implying their surfaces are old. On Vesta, we have now actually located the large impact craters that ejected the basaltic meteorites previously identified as coming from this asteroid. These craters are so large that they sample several layers of Vesta’s crustal material.
Ceres has not had a comparable history of giant impacts, so its surface is covered with craters that look more like those from the lunar highlands. The big surprise at Ceres is the presence of very bright white spots, associated primarily with the central peaks of large craters (Figure \(\PageIndex{11}\)). The light-colored mineral is some kind of salt, either produced when these craters were formed or subsequently released from the interior. After repeated close flybys, data from the NASA Dawn spacecraft indicated that Ceres has (or has had) a subsurface ocean of water, with occasional eruptions on the surface. The most dramatic is the 4 kilometer tall ice volcano called Ahuna Mons (see Figure \(\PageIndex{11}\)).
In late 2017, something entirely new was discovered: an interstellar asteroid. This visitor was found at a distance of 33 million kilometers with a survey telescope on Haleakala, Hawaii. As astronomers followed up on the discovery, it quickly became apparent that this asteroid was travelling far too fast to be part of the Sun’s family. Its orbit is a hyperbola, and when discovered it was already rapidly leaving the inner solar system. Although it was too distant for imaging by even large telescopes, its size and shape could be estimated from its brightness and rapid light fluctuations. It is highly elongated, with an approximately cylindrical shape. The nominal dimensions are about 200 meters in length and only 35 meters across, the most extreme of any natural object. Large objects, like planets and moons, are pulled by their own gravity into roughly spherical shapes, and even small asteroids and comets (often described as “potato-shaped”) rarely have irregularities of more than a factor of two.
This asteroid was named ‘Oumuamua, a Hawaiian word meaning “scout” or “first to reach out.” In a way, the discovery of an interstellar asteroid or comet was not unexpected. Early in solar system history, before the planet orbits sorted themselves into stable, non-intersecting paths all in the same plane, we estimate that quite a lot of mass was ejected, either whole planets or more numerous smaller fragments. Even today, an occasional comet coming in from the outer edges of the solar system can have its orbit changed by gravitational interaction with Jupiter and the Sun, and some of these escape on hyperbolic trajectories. As we have recently learned that planetary systems are common, the question became: where are similar debris objects ejected from other planetary systems? Now we have found one, and improved surveys will soon add others to this category.
Key Concepts and Summary
The solar system includes many objects that are much smaller than the planets and their larger moons. The rocky ones are generally called asteroids. Ceres is the largest asteroid; about 15 are larger than 250 kilometers and about 100,000 are larger than 1 kilometer. Most are in the asteroid belt between Mars and Jupiter. The presence of asteroid families in the belt indicates that many asteroids are the remnants of ancient collisions and fragmentation. The asteroids include both primitive and differentiated objects. Most asteroids are classed as C-type, meaning they are composed of carbonaceous materials. Dominating the inner belt are S-type (stony) asteroids, with a few M-type (metallic) ones. We have spacecraft images of several asteroids and returned samples from asteroid Itokawa. Recent observations have detected a number of asteroid moons, making it possible to measure the masses and densities of the asteroids they orbit. The two largest asteroids, Ceres and Vesta, have been extensively studied from orbit by the Dawn spacecraft.
Glossary
- asteroid
- a stony or metallic object orbiting the Sun that is smaller than a major planet but that shows no evidence of an atmosphere or of other types of activity associated with comets
- asteroid belt
- the region of the solar system between the orbits of Mars and Jupiter in which most asteroids are located; the main belt, where the orbits are generally the most stable, extends from 2.2 to 3.3 AU from the Sun
Contributors and Attributions
Andrew Fraknoi (Foothill College), David Morrison (NASA Ames Research Center), Sidney C. Wolff (National Optical Astronomy Observatory) with many 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/astronomy ).


5.2: Controls over Air Temperature
Temperature is a measure of the heat content of a body. It is a measure of the average speed of the random motion of molecules that comprise a substance. The air temperature at any place is determined by (1) radiation and heat transfers between the surface and the air above, (2) the location relative to a large body of water, and (3) the movement of vast pools of air called air masses.
Radiation, sensible heat and temperature
The air temperature at a place is determined by the exchange of radiant energy between the Sun, Earth, and its atmosphere. Solar radiation is the principle source of energy to heat the surface . Shortwave solar radiation easily penetrates to the surface without much absorption by the gases that comprise the atmosphere. As the sun heats the surface during the day, the earth warms and increases its output of infra red, or longwave radiation. The gases of the atmosphere, being relatively good absorbers of longwave radiation, are warmed and experience a rise in temperature. Thus, the immediate source of energy to heat the air is the surface of the earth. The daily cycle of radiation and air temperature is shown in Figure \(\PageIndex{1}\).
Solar radiation increases after sunrise to a maximum at noon and then decreases to a minimum at sunset. Outgoing radiation increases after sunrise but lags somewhat behind the insolation curve. The graph for air temperature follows the same pattern as that of outgoing radiation. This should seem reasonable as it is the absorption of outgoing energy from the surface that determines air temperature. The amount of time between maximum incoming energy and maximum temperature over the day is known as the daily temperature lag.
A similar type of lag occurs on an annual basis. The seasonal lag of temperature is the amount of time between the highest incoming insolation and highest temperature on an annual basis. For instance, in the midlatitudes the highest angle that the sun makes with the surface, and thus the most intense heating, occurs around June 22nd. It isn't until about a month later that the highest temperatures occur. The lag is often longer near a large body of water like the Great Lakes or the ocean. A temperature lag of two months is not uncommon for places located near large bodies of water.
Clouds have an impact on the radiation balance and air temperature of a place. Clouds can block incoming solar radiation by reflection of their tops. Clouds also act to diffuse light as it penetrates towards the surface. Both of these would act to cool the atmosphere. Clouds and water vapor are good absorbers of longwave radiation emitted by the earth's surface too. You've probably noticed that the warmest evenings tend to be when we have a heavy cover of clouds. These clouds absorb the radiation emitted by the earth and radiate it back down toward the earth's surface, warming the air. The coldest evenings occur during cloudless conditions. The lack of clouds in the desert creates large daily temperature ranges. During the day, sunlight streams to the earth's surface heating it to very high temperatures. Near surface air temperatures are very high as a result. At night, the absence of clouds allows emitted longwave radiation to escape to space causing the surface to cool and the air above to do so as well.
The atmosphere is also heated by the exchange of sensible heat between the surface and the air above. Sensible heat is transferred into the air by conduction and convection. Heat is most efficiently moved by turbulent eddies, or swirls of vertically moving air. The initial transfer is due to the presence of a temperature gradient between the surface and the air. If the surface of the earth is warmer than the air above, heat will be transferred upwards raising the temperature of the air. If the air is warmer than the surface, heat will be transferred towards the surface, thus cooling the air. The lag of temperature behind incoming radiation is also a result of the time it takes for sensible heat to transferred upwards.
Air Temperature, Water Bodies and Continentality
Air temperature is greatly affected by the location of a place relative to a large body of water. The impact of continental location on weather and climate characteristics of a place is called " continentality ". Air temperature near or over bodies of water is much different from that over land due to differences in the way water and land heat and cool. Properties that affect water temperature are:
- Transparency
- Allocation of Q*
- Ability to circulate
- Specific heat
Explore how each of these properties affect the temperature of air by clicking on the buttons below.
Air Temperature and Air Mass Movement
If radiation was the only cause of temperature at a place, the daily and seasonal cycle of temperature would be very regular and exhibit the temporal pattern discussed earlier. The movement of large air masses across the surface can drastically change all this. The movement of a very cold air mass into a region can drop temperatures during the day when we expect the highest temperatures. Or if a warm air mass streamed over us at night, we might experience the highest temperature of the past 24 hours during the evening hours rather than during the daytime.
An air mass is vast pool of air, covering thousands of square kilometers, having about the same humidity and temperature characteristics over its horizontal extent. Air masses are classified based on the temperature and humidity at their source region . Sources for air masses may be either oceanic or continental. Those that are oceanic tend to be moist while continental air masses are typically dry. Latitudinally, air masses form near the equator, in the subtropical zones, "polar" regions, and the Arctic and Antarctic. Most people think of the polar regions as those being located at the pole. For air masses, the polar source region is approximately 60 degrees north or south latitude. Combining the type of surface and latitude we derive a classification for the different kinds of air masses. A few are listed below and their geographic origin is shown in Figure \(\PageIndex{3}\). We'll deal with air masses in more detail when we investigate weather systems.
-
Maritime Tropical
(mT)
- Originates over the tropical oceans
- Warm and Moist
-
Continental Polar
(cP)
- Originates over high latitude continents (about 60 degrees north)
- Cold and dry
-
Maritime Polar
(mP)
- Originates over mid to high latitude oceans.
- Cool and moist
Influence of air masses on temperature at a place.
The influence that air masses have on the temperature of a place depends the location with respect to the source of the air mass and the trajectory of the air mass as it moves from its source region. For instance, if one is located in the heart of an air mass source region, your climate will be fairly uniform throughout the year. If you lived in north central Canada you are located in the heart of the continental polar air mass (cP). You should expect temperature to be cool to cold, and the humidity relatively low throughout much of the year. However, if you live in central Illinois, you will experience a much greater variation in temperature because you are in the boundary zone between several different air masses. Two air masses in particular influence this region, cP and mT. The cP air brings cool, dry weather while mT air is responsible for humid and warm conditions. When these air masses collide, storms are generated.
Inversions
Under normal circumstances, air temperature tends to decrease with increasing elevation above the surface through the troposphere. Under particular conditions the lapse rate of temperature is reversed and temperatures increase with increasing elevation creating an inversion or inverted lapse rate of temperature.
A radiation inversion commonly occurs when the evening air is still and there are no clouds to trap heat. Surface temperature drops as longwave radiation emitted by the Earth escapes to space. Air in contact with the surface cools, but that at a higher elevation and not in direct contact with the earth remains somewhat warmer creating the inversion. Cool air will collect in depressions as air density increases and gravity pulls it down slope.
Sea breeze inversions occur along windward coasts bordered by cold ocean currents. The bottom layer of a warm maritime air mass originating over the ocean becomes cooler upon coming in contact with the cooler water bordering the coast. This creates cooler air near the surface with warmer air aloft.
Areas dominated by high pressure are also subject to inversions. Subsidence inversions form when subsiding air undergoes adiabatic heating aloft, while air in contact with the surface remains cooler. Subsidence and subsidence inversions in association with high pressure are discussed in Chapter 6.


9.4: Substance Abuse
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– Criss Jami
Introduction
A drug is a chemical substance that can change how your body and mind work. Drugs of abuse are substances that people use to get high and change how they feel. They may be illegal drugs like pot, cocaine, or heroin. Or they may be legal for adults only, like alcohol and tobacco.
Medicines that treat illness can also become drugs of abuse when people take them to get high—not because they’re sick and following their doctor’s orders. People can even abuse cough or cold medicines from the store if they ignore the directions and take too much at one time.
People abuse drugs for many reasons:
- They want to feel good. Taking a drug can feel really good for a short time. That’s why people keep taking them—to have those good feelings again and again. But even though someone may take more and more of a drug, the good feelings don’t last. Soon the person is taking the drug just to keep from feeling bad.
- They want to stop feeling bad. Some people who feel very worried, afraid, or sad abuse drugs to try to stop feeling so awful. This doesn’t really help their problems and can lead to addiction, which can make them feel much worse.
- They want to do well in school or at work. Some people who want to get good grades, get a better job, or earn more money might think drugs will give them more energy, keep them awake, or make them think faster. But it usually doesn’t work, may put their health at risk, and may lead to addiction.
Cigarettes and Tobacco
It might surprise you to learn that cigarettes and other forms of tobacco are drugs. It’s legal to use tobacco once you’re 18 or 19 years old, depending on where you live. But it’s not healthy for you at any age.
Tobacco contains nicotine, a substance that excites the parts of the brain that make you feel good. You can get addicted to nicotine just like other drugs.
When you use tobacco, the nicotine quickly gives you a mild rush of pleasure and energy. But it soon wears off, which makes you want to use it some more. Sometimes, the rush of energy that comes with nicotine can make you nervous and edgy.
Electronic cigarettes: Read NIDA’s DrugFacts: Electronic Cigarettes (e-Cigarettes) for information about electronic cigarettes (sometimes called “vaping”), including how safe they are compared to tobacco cigarettes.
 These diseases can happen to people who smoke, or to others around them who breathe in their smoke.
Bad breath, bad teeth, mouth cancer : Cigarettes and other kinds of tobacco stain teeth and cause bad breath. Chewing tobacco can make teeth fall out and lead to cancer of the mouth.
Heart and blood problems : If you smoke, you are more likely to have a heart attack or stroke (sometimes called a “brain attack”).
Hurts babies : If a pregnant woman uses tobacco, her baby might be born too early or too small. This can cause health problems for the baby.
More diseases : Using cigarettes or other kinds of tobacco can lead to heart disease and many kinds of cancer.
Addiction : The nicotine in tobacco is what makes you addicted. When you smoke, the effects wear off quickly. This makes you want to keep using tobacco again and again throughout the day. The more you do this, the more your body and brain get addicted to the nicotine. Fortunately, there are medicines, other treatments, and hotlines that can help people quit tobacco.
Alcohol
Drinks like beer, malt liquor, wine, and hard liquor contain alcohol. Alcohol is the ingredient that gets you drunk.
Hard liquor—such as whiskey, rum, or gin—has more alcohol in it than beer, malt liquor, or wine.
The following drink sizes contain about the same amount of alcohol:
- 1 ½ ounces of hard liquor
- 5 ounces of wine
- 8 ounces of malt liquor
- 12 ounces of beer
Being drunk can make a person feel very silly, angry, or sad for no reason. It can make it hard to walk in a straight line, talk clearly, or drive.
Effects of Alcohol on the Body and Brain
- Brain: Alcohol interferes with the brain’s communication pathways and can affect the way the brain looks and works. These disruptions can change mood and behavior, and make it harder to think clearly and move with coordination.
- Heart: Drinking a lot over a long time or too much on a single occasion can damage the heart, causing problems such as stroke, high blood pressure, and arrhythmia.
- Liver: Heavy drinking takes a toll on the liver and can lead to a variety of problems such as alcoholic hepatitis, fibrosis, and cirrhosis
- Pancreas: Alcohol causes the pancreas to produce toxic substances that can eventually lead to pancreatitis, a dangerous inflammation and swelling of the blood vessels in the pancreas that prevents proper digestion.
- Cancer: Drinking too much alcohol can increase your risk of developing certain cancers, including cancers of the mouth, esophagus, throat, liver, and breast.
- Immune system: Drinking too much can weaken your immune system, making your body a much easier target for disease. Chronic drinkers are more liable to contract diseases like pneumonia and tuberculosis than people who do not drink too much. Drinking a lot on a single occasion slows your body’s ability to ward off infections—even up to twenty-hour hours after getting drunk.
So how much is “drinking too much”? The following guidelines are from the National Institute on Alcohol Abuse and Alcoholism:
Drinking Levels Defined
- Moderate alcohol consumption : According to the Dietary Guidelines for Americans, moderate drinking is up to 1 drink per day for women and up to 2 drinks per day for men.
- Binge drinking : Binge drinking is a pattern of drinking that brings blood alcohol concentration (BAC) levels to 0.08 g/dL. This typically occurs after 4 drinks for women and 5 drinks for men—in about 2 hours. Binge drinking has become a major health and safety issue on college campuses.
- Heavy drinking : Heavy drinking is defined as drinking 5 or more drinks on the same occasion on each of 5 or more days in the past 30 days.
- Low risk for developing an alcohol use disorder : For women, low-risk drinking is no more than 3 drinks on any single day and no more than 7 drinks per week. For men, it’s defined as no more than 4 drinks on any single day and no more than 14 drinks per week. NIAAA research shows that only about 2 in 100 people who drink within these limits have an alcohol use disorder. Even within these limits, you can have problems if you drink too quickly or have other health issues.
Certain people should avoid alcohol completely, including those who
- Plan to drive a vehicle or operate machinery
- Take medications that interact with alcohol
- Have a medical condition that alcohol can aggravate
- Are pregnant or trying to become pregnant
Marijuana
Marijuana is a green, brown, or gray mix of dried, crumbled leaves from the marijuana plant. It can be rolled up and smoked like a cigarette (called a joint) or a cigar (called a blunt). Marijuana can also be smoked in a pipe. Sometimes people mix it in food and eat it.
Marijuana can make you feel silly, relaxed, sleepy, and happy—or nervous and scared. It may change your senses of sight, hearing, and touch. It can also make it hard to think clearly.
Effects of Marijuana on the Body and Brain
These are just some of the problems marijuana can cause:
- Memory problems : Marijuana makes it hard to remember things that just happened a few minutes ago. That makes it hard to learn in school or to pay attention to your job. A recent study showed that if you begin regular marijuana use as a teen, you can lose an average of 8 IQ points, and do not get them back, even if you stop using the drug.
- Heart problems : Using marijuana makes the heart beat fast and raises your risk of having a heart attack.
- Coughing and breathing problems : Marijuana smokers can get some of the same coughing and breathing problems as cigarette smokers. Marijuana smoke can hurt your lungs.
- Drugged driving : Driving when you’re high on marijuana is dangerous, just like driving drunk. Your reactions to traffic signs and sounds are slow. It’s hard to pay attention to the road. And it’s even worse when you’re high on marijuana and alcohol at the same time.
- You stop caring : Over time, marijuana users can get “burnt out.” They don’t think about much or do much. They can’t concentrate. They don’t seem to care about anything.
- Addiction : Although some people don’t know it, you can get addicted to marijuana after using it for a while. This is more likely to happen to people who use marijuana every day, or who started using it when they were teenagers.
Cocaine (Coke, Crack)
Cocaine is a white powder. It can be snorted up the nose or mixed with water and injected with a needle. Cocaine can also be made into small white rocks, called crack. It’s called crack because when the rocks are heated, they make a cracking sound. Crack is smoked in a small glass pipe.
Cocaine can make a person feel full of energy, but also restless, scared, or angry.
Effects of Cocaine on the Body and Brain
These are just some of the problems cocaine can cause:
- You feel sick : Cocaine can cause stomach pain and headaches. It can make you shake, throw up, or pass out.
- No appetite : Cocaine can make you not want to eat. Over time, you might lose a lot of weight and get sick.
- Heart attack and stroke : Cocaine raises your blood pressure and makes your heart beat faster. This can hurt your heart. It can give you a heart attack or stroke (brain injury from a blood clot). Some people die because of it.
- HIV/AIDS, hepatitis : People who inject (shoot up) cocaine can get HIV/AIDS and hepatitis (a liver disease) if they share used needles. People also get these diseases by having unsafe sex. They may forget to use condoms because they’re high on the drug.
- Addiction : It is easy to lose control over cocaine use and become addicted. Then, even if you get treatment, it can be hard to stay off the drug. People who stopped using cocaine can still feel strong cravings for the drug, sometimes even years later.
Heroin
Heroin is a white or brown powder or a black, sticky goo. It can be mixed with water and injected with a needle. Heroin can also be smoked or snorted up the nose.
Heroin causes a rush of good feelings just after it’s taken. But some people throw up or itch after taking it. For the next several hours you want to sleep, and your heart rate and breathing slow down. Then the drug wears off and you may feel a strong urge to take more.
Effects of Heroin on the Body and Brain
These are just some of the problems heroin can cause:
- Sick and itchy : Heroin can make you throw up and feel very itchy.

- HIV/AIDS, Hepatitis : Sharing used needles to inject (shoot up) heroin can give you HIV/AIDS and hepatitis (a liver disease).
- Overdose : People overdose on heroin because they can’t tell how strong it is until they take it. Signs of a heroin overdose are slow breathing, blue lips and fingernails, cold clammy skin, and shaking. You can die from a heroin overdose. People who might be overdosing should be taken to the emergency room immediately.
- Coma : Heroin can put you in a coma. That’s when nothing can wake you up, and you may die.
- Addiction : It is very easy to become addicted to heroin. Then, even if you get treatment, it’s hard to stay away from the drug. People who stopped using heroin can still feel strong cravings for the drug, sometimes years later. Fortunately, there are medicines that can help someone recover from heroin addiction.
Meth (Crank, Ice)
Methamphetamine—meth for short—is a white, bitter powder. Sometimes it’s made into a white pill or a clear or white shiny rock (called a crystal).
Meth powder can be eaten or snorted up the nose. It can also be mixed with liquid and injected into your body with a needle. Crystal meth is smoked in a small glass pipe.
Meth at first causes a rush of good feelings, but then users feel edgy, overly excited, angry, or afraid. Their thoughts and actions go really fast. They might feel too hot.
Effects of Meth on the Body and Brain
These are just some of the problems meth can cause:
- You overheat : Meth can make your body temperature so hot that you pass out.
- Crank bugs : Meth can make you feel like bugs are crawling on or under your skin. It makes you scratch a lot. Scratching causes sores on your face and arms.
- Meth mouth : Meth users’ teeth become broken, stained, and rotten. Meth users often drink lots of sweet things, grind their teeth, and have dry mouth. This is called “meth mouth.”
- You look old : People who use meth start looking old. Meth users burn a lot of energy and don’t eat well. This can make them lose weight and look sick. Their hands or body might shake. Their skin looks dull and has sores and pimples that don’t heal. Their mouth looks sunken as the teeth go bad.
- HIV/AIDS, Hepatitis : People who inject (shoot up) meth can get HIV/AIDS or hepatitis (a liver disease) if they share used needles. People also get these diseases by having unsafe sex. They often forget to use condoms because they’re high on the drug.
- Addiction : Meth use can quickly lead to addiction and hurt different parts of your brain. It can cause thinking and emotional problems that don’t go away or that come back again even after you quit using the drug. For instance, you might feel, hear, or see things that aren’t there. You might think that people are out to get you, or start believing strange ideas that can’t really be true.
Prescription Pain Medicine (OxyContin, Vicodin)
Pain medicines relieve pain from surgery or injuries. You need a prescription from a doctor to buy some strong kinds of these medicines. Prescription pain medicines are legal and helpful to use when a doctor orders them to treat your medical problem.
But people sometimes take these without a doctor’s prescription to get high or to try to treat themselves or their friends. Drug dealers sell these pills just like they sell heroin or cocaine. Some people borrow or steal these pills from other people.
Some people think that prescription pain medicines are safer to abuse than “street” drugs because they are medicines. Prescription pain medicine abuse can be as dangerous as heroin or cocaine abuse.
Oxycodone is one pain medicine that people often abuse. Sometimes it goes by the brand names OxyContin ® or Percocet ® . Another one that is often abused is hydrocodone. One of its brand names is Vicodin ® .
Pain medicines are usually white, round, or oval pills. They can be taken whole, smoked, or crushed into a powder that is snorted or injected.
Like heroin, pain pills can cause a rush of good feeling when they’re first taken, but they can also make you want to throw up. They can make you very sleepy, and you can get addicted to them.
Effects of Pain Medicine Abuse on the Body and Brain
These are just some of the problems pain medicine abuse can cause:
- You stop breathing : Pain medicine abuse can slow down or even stop your breathing.
- Coma : Pain medicine abuse can put you in a coma. That’s when nothing can wake you up.
- Addiction : Prescription pain medicines can be as addictive as heroin—especially if they are smoked or injected. Then, even if you get treatment, it’s hard to stay away from the drug. Fortunately, there are medicines that can help someone recover from prescription pain medicine addiction.
- Overdose : Signs of a pain medicine overdose are cold and sweaty skin, confusion, shaking, extreme sleepiness, trouble breathing, and coma.
- Death : Many people die from pain medicine overdoses. In fact, more people overdose from pain medicines every year than from heroin and cocaine combined.
Other Drugs of Abuse
There are many other drugs of abuse, including:
Ecstasy (X, E, XTC) is a pill that is often taken at parties and clubs. It is sometimes called the “love drug” because it makes people feel very friendly and touchy. It also raises body temperature, heart rate, and blood pressure, and can make you feel sad for days after its effects wear off. Click here for more information about ecstasy.
K2 or Spice (fake weed, Skunk) is a drug made from shredded dried plant materials and chemicals. It is usually smoked. The “high” feels about the same as the “high” from marijuana. Spice users sometimes end up in the emergency room with rapid heart rates, vomiting and other uncomfortable side effects. K2/Spice is illegal. Click here for more information about K2/Spice.
LSD (acid) comes in pills or on small pieces of paper that have been soaked in liquid LSD. It makes you see, hear, and feel things that aren’t there. You might see bright colors, pretty pictures, or things that scare you. Click here for more information about LSD.
PCP (angel dust) is a pill or powder that can be eaten, smoked, or snorted up the nose. It makes people feel far away from the world around them. PCP often makes people feel angry and violent, not happy and dreamy. Click here for more information about PCP.
Inhalants are dangerous chemicals that make you feel high when you breathe them into your lungs (also called huffing or sniffing). These chemicals are found in household cleaners, spray cans, glue, and even permanent markers.  Click here for more information about inhalants.
Club Drugs
Some drugs are called “club drugs” because they are sometimes passed around at nightclubs and parties:
- GHB is a liquid or powder that can make you pass out. It’s called a “date rape” drug because someone can secretly put it in your drink. This means that you can’t fight back or defend yourself.
- Rohypnol (roofies) is a date rape pill and can also be put in a drink.
- Ketamine (K, Special K) makes you feel far away from what’s going on around you and can feel scary and unpleasant. It is usually taken by mouth, snorted up the nose, or injected with a needle.
- Click here for more information about these drugs.
Bath Salts are drugs made with chemicals like the “upper” found in the Khat plant. They are only sold with the name “Bath Salts” to make them look harmless. These drugs can make you “high” but they can also make you shaky, afraid, and violent.  They can be taken by mouth, by inhaling into the lungs, or with a needle. Some people end up in the emergency room or even die after taking bath salts. Click here for more information about bath salts.
When and Where to Get Help
Here’s a simple way to think about substance use and abuse: If your use of drugs or alcohol is interfering with your life—negatively affecting your health, work, school, relationships, or finances—it’s time to quit or seek help. People who are addicted to a substance continue to abuse even though they know it can harm their physical or mental health, lead to accidents, or put others in danger. The following video dispels some myths about who is at risk of addiction:
Video: Anyone Can Become Addicted to Drugs
A YouTube element has been excluded from this version of the text. You can view it online here: https://press.rebus.community/blueprint2/?p=245
Know that first six weeks of the first semester is an especially critical and vulnerable time for most first-year students. Because lots of students get into the habit of drinking heavily and partying during these early days of college, there’s a risk that excessive alcohol consumption will interfere with successful adaptation to campus life. The transition to college is often difficult, and about one-third of first-year students fail to enroll for their second year.
If you are concerned about your drug or alcohol use, or you need help quitting, visit the student health center or talk with your college counselor. These folks are there to help you—it’s their job to provide information and support.
If you need additional resources or help, the following are good places to check:
- Drug Information Online
- Prevention Hub
- Drug and Alcohol Treatment Hotline: 1-800-662-HELP
Activity: When and Where to Get Help for Substance Abuse
Objectives
- Explain what substance use and abuse is and identify the warning signs that help may be needed
- Identify resources for further information and guidance about substance abuse
Directions
- Pick a topic: Choose alcohol or one of the drugs discussed in this section on Substance Abuse.
- Consider the following scenario: You suspect that one of your college friends may be abusing this drug. Your goal is to educate yourself about the signs of abuse and collect resources that you can share with him/her.
-
Visit one of the following Web sites to get initial relevant information on your topic. You can research other sites, if you chose a topic that’s not listed here.
- Cigarettes/Tobacco
- Alcohol
- Marijuana
- Cocaine
- Heroin
- Meth
- Prescription Pain Medicines
- Research additional sites to identify local resources where someone like your friend might go, or places to call, for help.
-
Creative writing assignment: Write a 2-page letter to the fictional friend in which you share your concerns about his/her behavior and offer to help. Be sure to touch on the following:
- The type of substance
- The behavior(s) you’ve noticed your friend engaging in that worry you and cause you to suspect a substance abuse problem
- The source of your information, which you’re sharing with your friend. For example: “I learned about the signs of heroin abuse from this Web site: . . .”
- Why you think your friend should quit using or cut down
- Your suggestions for what your friend should do and where to seek help. Give the names and contact information for at least 3 resources/organizations you found.
- Follow your instructor’s guidelines for submitting assignments.
Licenses and Attributions:
CC licensed content, Original:
- Substance Abuse. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/suny-collegesuccess-lumen1/chapter/substance-abuse/ License: CC BY: Attribution
Public domain content:
- Drugs That People Abuse. Provided by: NIH, NIAAA . Located at: easyread.drugabuse.gov/content/drugs-people-abuse. License: Public Domain: No Known Copyright
- What Is Addiction. Provided by: NIH. Located at: nihseniorhealth.gov/drugabuse...gabuse/01.html. License: Public Domain: No Known Copyright
- Fall Semester-A Time For Parents To Revisit Discussions About College Drinking. Provided by: NIH, NIAAA. Located at: http://www.collegedrinkingprevention.gov/NIAAACollegeMaterials/collegeFactSheetForParents.aspx . License: Public Domain: No Known Copyright
Adaptions: Removed images, relocated learning objectives.


6.3.4: Interpreting Inequalities
Lesson
Let's write inequalities.
Exercise \(\PageIndex{1}\): Solve Some Inequalities!
For each inequality, find the value or values of \(x\) that make it true.
- \(8x+21\leq 56\)
- \(56<7(7-x)\)
Exercise \(\PageIndex{2}\): Club Activities Matching
Choose the inequality that best matches each given situation. Explain your reasoning.
-
The Garden Club is planting fruit trees in their school’s garden. There is one large tree that needs 5 pounds of fertilizer. The rest are newly planted trees that need \(\frac{1}{2}\) pound fertilizer each.
- \(25x+5\leq\frac{1}{2}\)
- \(\frac{1}{2}x+5\leq 25\)
- \(\frac{1}{2}x+25\leq 5\)
- \(5x+\frac{1}{2}\leq 25\)
-
The Chemistry Club is experimenting with different mixtures of water with a certain chemical (sodium polyacrylate) to make fake snow.
To make each mixture, the students start with some amount of water, and then add \(\frac{1}{7}\) of that amount of the chemical, and then 9 more grams of the chemical. The chemical is expensive, so there can’t be more than a certain number of grams of the chemical in any one mixture.- \(\frac{1}{7}x+9\leq 26.25\)
- \(9x+\frac{1}{7}\leq 26.25\)
- \(26.25x+9\leq\frac{1}{7}\)
- \(\frac{1}{7}x+26.25\leq 9\)
-
The Hiking Club is on a hike down a cliff. They begin at an elevation of 12 feet and descend at the rate of 3 feet per minute.
- \(37x-3\geq 12\)
- \(3x-37\geq 12\)
- \(12-3x\geq -37\)
- \(12x-37\geq -3\)
-
The Science Club is researching boiling points. They learn that at high altitudes, water boils at lower temperatures. At sea level, water boils at \(212^{\circ}\text{F}\). With each increase of 500 feet in elevation, the boiling point of water is lowered by about \(1^{\circ}\text{F}\).
- \(212-\frac{1}{500}e<195\)
- \(\frac{1}{500}e-195<212\)
- \(195-212e<\frac{1}{500}\)
- \(212-195e<\frac{1}{500}\)
Exercise \(\PageIndex{3}\): Club Activities Display
Your teacher will assign your group one of the situations from the last task. Create a visual display about your situation. In your display:
- Explain what the variable and each part of the inequality represent
- Write a question that can be answered by the solution to the inequality
- Show how you solved the inequality
- Explain what the solution means in terms of the situation
Are you ready for more?
\(\left\{ 3,4,5,6\right\}\) is a set of four consecutive integers whose sum is 18.
- How many sets of three consecutive integers are there whose sum is between 51 and 60? Can you be sure you’ve found them all? Explain or show your reasoning.
- How many sets of four consecutive integers are there whose sum is between 59 and 82? Can you be sure you’ve found them all? Explain or show your reasoning.
Summary
We can represent and solve many real-world problems with inequalities. Writing the inequalities is very similar to writing equations to represent a situation. The expressions that make up the inequalities are the same as the ones we have seen in earlier lessons for equations. For inequalities, we also have to think about how expressions compare to each other, which one is bigger, and which one is smaller. Can they also be equal?
For example, a school fundraiser has a minimum target of $500. Faculty have donated $100 and there are 12 student clubs that are participating with different activities. How much money should each club raise to meet the fundraising goal? If \(n\) is the amount of money that each club raises, then the solution to \(100+12n=500\) is the minimum amount each club has to raise to meet the goal. It is more realistic, though, to use the inequality \(100+12n\geq 500\) since the more money we raise, the more successful the fundraiser will be. There are many solutions because there are many different amounts of money the clubs could raise that would get us above our minimum goal of $500.
Glossary Entries
Definition: Solution to an Inequality
A solution to an inequality is a number that can be used in place of the variable to make the inequality true.
For example, 5 is a solution to the inequality \(c<10\), because it is true that \(5<10\). Some other solutions to this inequality are 9.9, 0, and -4.
Practice
Exercise \(\PageIndex{4}\)
Priya looks at the inequality \(12-x>5\) and says “I subtract a number from 12 and want a result that is bigger than 5. That means that the solutions should be values of that are smaller than something.”
Do you agree with Priya? Explain your reasoning and include solutions to the inequality in your explanation.
Exercise \(\PageIndex{5}\)
When a store had sold \(\frac{2}{5}\) of the shirts that were on display, they brought out another 30 from the stockroom. The store likes to keep at least 150 shirts on display. The manager wrote the inequality \(\frac{3}{5}x+30\geq 150\) to describe the situation.
- Explain what \(\frac{3}{5}\) means in the inequality.
- Solve the inequality.
- Explain what the solution means in the situation.
Exercise \(\PageIndex{6}\)
You know \(x\) is a number less than 4. Select all the inequalities that must be true.
- \(x<2\)
- \(x+6<10\)
- \(5x<20\)
- \(x-2>2\)
- \(x<8\)
(From Unit 6.3.1)
Exercise \(\PageIndex{7}\)
Here is an unbalanced hanger.
- If you knew each circle weighed 6 grams, what would that tell you about the weight of each triangle? Explain your reasoning.
- If you knew each triangle weighed 3 grams, what would that tell you about the weight of each circle? Explain your reasoning.
(From Unit 6.3.1)
Exercise \(\PageIndex{8}\)
Match each sentence with the inequality that could represent the situation.
- Han got $2 from Clare, but still has less than $20.
- Mai spent $2 and has less than $20.
- If Tyler had twice the amount of money he has, he would have less than $20.
- If Priya had half the money she has, she would have less than $20.
- \(x-2<20\)
- \(2x<20\)
- \(x+2<20\)
- \(\frac{1}{2}x<20\)
(From Unit 6.3.1)
Exercise \(\PageIndex{9}\)
At a skateboard shop:
- The price tag on a shirt says $12.58. Sales tax is 7.5% of the price. How much will you pay for the shirt?
- The store buys a helmet for $19.00 and sells it for $31.50. What percentage was the markup?
- The shop pays workers $14.25 per hour plus 5.5% commission. If someone works 18 hours and sells $250 worth of merchandise, what is the total amount of their paycheck for this pay period? Explain or show your reasoning.
(From Unit 4.3.3)


1.20: SIM Medium
The student will:
- Use aseptic techniques in the safe inoculation of various forms of media.
- Follow oral and written instructions and manage time in the lab efficiently.
- Apply correct terminology regarding microbiological techniques, instruments, microbial growth, biochemical testing, media types and forms when making observations.
- Correctly perform various inoculation techniques and describe each technique’s purpose.
- Make accurate observations and appropriate interpretations of biochemical test results and use them in the identification of potentially disease causing microbes.
SIM is an example of a combination medium , meaning that one can determine several bacterial activities/characteristics through the use of one medium. SIM medium tests for s ulfur reduction, i ndole production and m otility. The form of medium used for this test is an agar deep . SIM Medium contains the following: pancreatic digest of casein, peptic digest of animal tissue, ferrous ammonium sulfate \(\ce{Fe(NH4)2(SO4)}\), sodium thiosulfate \(\ce{Na2S2O3}\), agar (3.5 g/L) and distilled water.
Sulfur can be reduced producing hydrogen sulfide by bacteria in two unrelated ways. One process occurs during putrefaction. When proteins putrefy, the resulting foul “rotten egg” smell is due to the production of hydrogen sulfide gas, \(\ce{H2S}\). Hydrogen sulfide is a byproduct of the conversion of the amino acid cysteine to pyruvate by the enzyme cysteine desulfurase . The second mode of \(\ce{H2S}\) generation involves anaerobic respiration. In some prokaryotes, thiosulfate (\(\ce{S2O3^{2-}}\)) is the terminal electron acceptor in an anaerobic ETS. When thiosulfate is reduced (picks up electrons) the result is \(\ce{H2S}\) gas. In either case, invisible \(\ce{H2S}\) gas is produced.
Because hydrogen sulfide gas is colorless (though not odorless!) SIM medium uses an indicator reaction. Iron (supplied by ferrous ammonium sulfate) in the medium combines with \(\ce{H2S}\) gas to form iron sulfide, FeS, a black precipitate. Any black color in the medium is a positive test for sulfur reduction. Unfortunately, this test does not distinguish between the hydrogen sulfide produced as a result of putrefaction and hydrogen sulfide produced at the end of an anaerobic ETS.
Indole is produced during the conversion of tryptophan, an amino acid, to pyruvate and ammonia by the enzyme tryptophanase . Indole production indicates tryptophanase activity. Kovac’s reagent, added after incubation, will turn pink when it combines with indole.
Motility is the ability of a microbe to “swim” using flagella. The reduced agar content of this medium, 3.5 g/L compared to 12-15 g/L in most solid media, creates a semi liquid environment allowing motile cells to spread from their original placement. The stab technique (see the description below) deposits cells in a straight line down the center of the deep. If growth is observed beyond the stab line into the periphery of the tube, the test is positive for motility. Avoid confusing growth produced by the lateral movement of the needle during an imperfect stab inoculation with actual motility. Rotating the tube for a side view and comparing each experimental tube to the uninoculated tube will help you determine if growth is confined to the original inoculation line, or has truly spread into the periphery of the tube.
Stab Inoculation
- Aseptically obtain cells on the end of the inoculating needle
- Holding the deep tube in your non-dominant hand, remove the cap and flame the mouth of the tube as you normally do with a tube.
- Holding the needle vertically, stab the agar straight down the center to within a quarter inch of the bottom. Then draw it straight back out of the tube. Try to follow the original stab line when removing the needle.
- Again, heat the mouth of the tube after withdrawing the transfer instrument. Replace the cap loosely and set the tube in the test tube rack.
- Immediately flame the inoculating needle for a full 10 seconds before setting it down.
Materials per student pair
2 SIM deep tubes
Inoculating needle
Lab 2: Indole reagent (Kovac’s)
Cultures
Serratia marcescens
E. coli
Procedure Lab 1
- Label your tubes with each of the organisms. Don’t forget to include the other components of the label.
- Aseptically obtain an inoculum from each culture.
- Aseptically stab inoculate the corresponding tubes.
- Place the tubes for incubation for 24-48 hours at 37 o C.
Procedure Lab 2
- Make observations for sulfur reduction and motility first. As in the other DT exercises, observations are what you see, result is “+” or “-“and interpretation refers to the result’s meaning.
- In the sulfur reduction data table, observe the location of any black color.
- For motility, it helps to compare the experimental tubes with the sham inoculated tube. Hold a paper with small print behind the tubes. Try to read the printing through the tubes. By comparing the inoculated tubes with an uninoculated tube you can determine if there is radiating (fuzzy) growth from the stab line. Be sure that you can distinguish between non-motile growth confided to the stab line (in 2 dimensions) and actual radiating growth, 360 o around the inoculation.
- After you have observed motility and sulfur reduction, you can add the reagent for the indole test. The Kovac’s reagent is kept in the hood.
- Place 3-4 drops of the reagent on the agar surface. Replace the test tube cap. If indole is present, you will see a pink color develop within 2-3 minutes.
- When finished, place your experimental tubes in the biohazard waste.


34.6: I’m Not the Right Person to Be Talking About This
What’s astounding to me as a reader is the persistent presence of the white savior both across genres and across decades. An obviously problematic concept, it attempts to if not alleviate, maybe even rectify white guilt and bestow a sense of both power and purpose upon consumers of media. Civil rights becomes a pastime and a source of entertainment for the audience, but if this is the case, is there a proper way to include white characters into a story? It could be helpful as a call to action, as persons in a position of power certainly have the means to disassemble a racist society… but is that my conditioning as a white person to believe that the ability to adjust power imbalance lies in the hands of the oppressor?
Therein lies the problem. Is it our privilege as white audiences (and critics) to discuss civil rights and slavery from an almost impartial, critical point of view? While anyone who graduated second grade could tell you “racism is bad,” the line becomes blurry when people- even with the best intentions- attempt to tell or explain stories that are not ours to tell. Doing so inherently takes the power and ownership from African Americans and puts it in the hands of someone maybe at one time more societally equipped to handle the consequences. Now, however, because of digital media and participatory culture, that sentiment has become not only unnecessary, but harmful altogether. The production of mass media has permitted the belief in equality as a fashionable and not particularly difficult concept. The oversimplification of intersectionality as a practice of tolerating non-white people living in our world rather than genuine interracial harmony is present.
The Help , a 2011 film adaption of the popular novel, was directed and produced by, not one, but four white people- three of whom were men. The woman who wrote the novel was also white. The female protagonist is- you guessed it- also white. It’s no secret that the film was attempting to appeal to “alternative” white kids. You, too, can be the quirky, bleeding heart lead in your own story! It matters that this is a film because the ultimate goal of the industry is to sell. With that goal comes pandering to whichever group of people is the most likely to buy into it. The film could only exist during a time when racial equality and social justice is trendy. This intention inherently warps the integrity of the media being produced; it’s only done with the approval of consumers in mind. It influences the way characters interact and the outcome of the plot. This is, unfortunately, not a new trend.
Frederick Douglass’ The Heroic Slave is a fictional narrative about the Creole rebellion before the Civil War. It also features a white narrator obtaining a sense of purpose and a freer conscience through the assistance of an escaped slave who ignites a rebellion. We’ve discussed some of the issues and compelling qualities of the text, but it differs from The Help in a few ways. Because it was written by a black author, it possesses an anxious need to humanize Madison Washington. This is done through- again- his relationship to white characters over and over again.  The implication is that the rebellion wouldn’t have been possible without the assistance of the white narrator. For the era, this was necessary for many of the same reasons as The Help: it had to appeal to white audiences.
The Help features black characters without considering how those black characters fall into or perpetuate stereotypes. Yes, some characters present are full and outrageously kind. But they can only exist in their relationship to the white characters. The story is called The Help , and whether it’s irony or not it’s still identifying the entirety of the black presence in the story by their status as maids. There’s a subconscious implication here that equality is only worth working towards within the context of whites maintaining their privilege. One of the characters has a brutal domestic violence scene, which falls into a stereotype of its own. While The Heroic Slave involves (to some degree) the empowerment of the oppressed, The Help features continuous scenarios of black people being oppressed and unable to fight back, including the all-too-topical police brutality scene. Compare this to a film like Black Panther, which includes an almost entirely black cast and was one of the most-watched movies of all time. The white presence is just not necessary, so logically one could surmise that the empowerment of black characters on their own is threatening to white producers. The cop-out, the easy solution- is becoming less popular and less acceptable.
Because of the release of The Help during the era of the internet, there’s immensely more pressure to blindly agree with the film. The nature of mass media is inherently participatory, but this only means that each individual has a consistent and readily available audience. Consequentially, each individual is subject consistent and readily given criticism. It makes critical discussion about problematic aspects of a film which is technically diverse a much more socially dangerous conquest. Additionally, it’s difficult to navigate exactly who lays claim to the right to criticize diverse media. Everyone has an equal voice, but not all opinions are created equal. A white person who has little to no experience navigating racially charged social interactions is going to see fewer issues than someone who has tons. The presence of the white leading lady and the entirely white production team makes it clear that The Help was produced by and for white audiences to be shallowly consumed, as the accessibility of the internet to people of color has made it significantly easier to share their points of view without the presence of a white narrator, and therefore the aforementioned plot device is not necessary as it was when The Heroic Slave was written.


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2.1: OER Collections
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So, how can we find collections of OERs? These resources are not just textbooks. Through Creative Commons licensing, any resource made with the intent to be used within education can be designated as an OER, including textbooks, lecture notes, quizzes, videos, and other educational materials that are available for anyone to use, adapt, and share.
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2.2: Strategies for Finding OERs
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From known what kind of keywords to use, to where to start looking for OERs, knowing a few search strategies will make for more effective searching. Watch the following short video and then review the search tips below so you can use them as you search for resources for your class.
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2.3: Open Licensing and Creative Commons Primer
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This resource is a condensed adaptation of the Open Educational Resources: OER 101 Tutorials for Designers. Providing explanations behind what Open Educational Resources (OER) are, how Creative Commons impacts it, and the meaning and ideology of "Open".
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2.4: Strategies and Keeping Track of OERs
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A course organization spreadsheet can help you organize and keep track of the resources for your course. The spreadsheet has room for all the information you will need to organize your course. The more completely you fill it out, the easier it will be when you are ready to make a single resource or integrate them into your online course.


7.10.2: Thought Questions
Thought Questions
What can we learn about the formation of our solar system by studying other stars? Explain.
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Earlier in this chapter, we modeled the solar system with Earth at a distance of about one city block from the Sun. If you were to make a model of the distances in the solar system to match your height, with the Sun at the top of your head and Pluto at your feet, which planet would be near your waist? How far down would the zone of the terrestrial planets reach?
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Seasons are a result of the inclination of a planet’s axial tilt being inclined from the normal of the planet’s orbital plane. For example, Earth has an axis tilt of 23.4° (Appendix F). Using information about just the inclination alone, which planets might you expect to have seasonal cycles similar to Earth, although different in duration because orbital periods around the Sun are different?
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Again using Appendix F, which planet(s) might you expect not to have significant seasonal activity? Why?
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Again using Appendix F, which planets might you expect to have extreme seasons? Why?
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Using some of the astronomical resources in your college library or the Internet, find five names of features on each of three other worlds that are named after real people. In a sentence or two, describe each of these people and what contributions they made to the progress of science or human thought.
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Explain why the planet Venus is differentiated, but asteroid Fraknoi, a very boring and small member of the asteroid belt, is not.
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Would you expect as many impact craters per unit area on the surface of Venus as on the surface of Mars? Why or why not?
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Interview a sample of 20 people who are not taking an astronomy class and ask them if they can name a living astronomer. What percentage of those interviewed were able to name one? Typically, the two living astronomers the public knows these days are Stephen Hawking and Neil deGrasse Tyson. Why are they better known than most astronomers? How would your result have differed if you had asked the same people to name a movie star or a professional basketball player?
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Using Appendix G, complete the following table that describes the characteristics of the Galilean moons of Jupiter, starting from Jupiter and moving outward in distance.
| Moon | Semimajor Axis (km 3 ) | Diameter | Density (g/cm 3 ) |
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| Io | |||
| Europa | |||
| Ganymede | |||
| Callisto |
This system has often been described as a mini solar system. Why might this be so? If Jupiter were to represent the Sun and the Galilean moons represented planets, which moons could be considered more terrestrial in nature and which ones more like gas/ice giants? Why? (Hint: Use the values in your table to help explain your categorization.)