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| Class Activities |
Chapter 3: The Chemistry Of Biology |
1. Relevance of Topic
In making the topic of chemistry relevant to life, pharmacology topics, food additives and preservatives, lawn care or agricultural products, beauty care and hygiene products, could all be discussed.
To illustrate how chemistry is relevant to biology, use a DNA model, or picture thereof, for illustrating the relevance of chemical bonding, types of bonds, and types of structures (e.g. atoms, molecules, polymers) to living organisms or cells.
2. Continuity
The Chemistry of Biology chapter introduces the specific components and fundamental principles that are required for the rest of the chapters in Part I of the text. For instance, the chapter immediately following this one is on polymers and proteins. An understanding of basic chemical principles is necessary for students to get the most out of the rest of this section.
3. Demonstration Activities
Text section 3.1
1. Use the Periodic Table to discuss elements, their properties, and the reasons they are organized into periods and families. The fact that Mendeleev died before all the currently known elements had been discovered, and that he left blank spaces for the undiscovered ones, and predicted their properties, is particularly interesting.
2. Have samples of several elements: copper, lead, sulfur, aluminum, iodine, mercury, and iron, are easy to obtain. Also, pictures of several elements in pure form are commonly available, or one could show how elements are used in everyday life: a helium balloon, a neon sign, oxygen in a hospital tank, carbon in a diamond ring, carbon in pencil graphite, mercury in a thermometer, silver, gold, and platinum in jewelry.
3. Use chalk and the board, or transparencies, or drawing programs, in discussing atomic structure and atomic particles.
4. To illustrate the formation of compounds from elements, a demonstration of the reaction between pure chlorine gas and pure sodium solid, to form NaCl, is a dramatic and fun demonstration. It also drives home very clearly the principle that the properties of a compound are radically different from the properties of its constituent elements.
5. In discussing isotopes, carbon dating is particularly relevant to biology, as is the use of isotopes in medical studies. Show pictures relevant to these topics.
Text section 3.2
1. Covalent bonds are the principal topic of this section, and are responsible for water, carbon dioxide, methane, ammonia, and other important biological molecules. There are several chemistry demonstrations that can be done to show either the making or the breaking of the bonds in these molecules. Consider consulting a chemistry text for specific guidance.
Text section 3.3
1. Ionic bonding is responsible for the making of salts (e.g. NaCl), and one or several demonstrations could be done to show this in action. Alternatively, one could merely refer to the biological relevance of these compounds and of ions generally (e.g. sodium channels). Visuals could include drawings of orbitals, with emphasis on the octet rule and how atoms become stable when their orbitals are filled.
Text section 3.4
1. To teach Avogadro's number, use an analogous and easily understood quantity: a dozen. For example, one might have a dozen eggs, or one might have Avogadro's number of eggs (6 x 1023 eggs). The point is that this number is merely used for counting. Once this point about the number is made, state the convention that one mole equals Avogadro's number of anything. That is, 6 x 1023 eggs is a mole of eggs, just as 12 eggs is a dozen eggs.
2. There are many demonstrations for chemical reactions; the sodium and chlorine reaction to make salt is again useful here. Something less dangerous and easy to do is to drop an iron nail into a bright blue solution of copper sulfate and find, one day later, that the iron has replaced the copper, forming a brown solution of iron sulfate, and leaving pure copper as a precipitate in the bottom of the container. This simple replacement reaction can also emphasize the use of the Periodic Table to predict how reactions will go, due to the respective valences of the atoms.
Text section 3.6
1. An easy and colorful demonstration is that of an acid-base titration with an indicator such as phenolphthalein.
Text section 3.7
1. Use pH paper or a pH meter to test the acidity or alkalinity of various common substances: vinegar, soda pop, lemon juice, ammonia cleaning agents. Test the pH of these substances, then add sodium bicarbonate (pure reagent, or Alka-Seltzer for a more relevant discussion) to acidic ones, or sodium bisulphate to alkaline ones, and retest.
Text section 3.8
1. Cohesion can be demonstrated by showing water puddling on a flat surface.
2. Adhesion can be demonstrated by showing the meniscus formed when water is in a tube, or by pouring water out of a beaker along a glass rod into another container.
3. Surface tension can be demonstrated (Figure 3.6) with photographs, or by placing small bits of paper onto the surface of water in a pan or wide container.
4. The heat capacity of water is important to warm-blooded animals, as it helps them maintain a constant temperature. To get across the meaning of heat capacity, ask students which gets colder faster, a bowl of hot soup, or a slice of hot toast? The answer is the toast, because of the high amount of water in the soup. Or, ask why water in lakes and ponds does not freeze right away when the air temperature suddenly drops to below freezing.
5. Heat of vaporization, heat of fusion, and other properties of water, can be illustrated by referring to Figures 3.7, 3.8, and 3.9.
Text section 3.9
1. Hydrocarbons, isomers, and other topics in this section are easily illustrated with either ball and stick models or with text figures.
Text section 3.10
1. Either ball and stick models or computer-generated animation can be used for showing shapes in three dimensions and for discussing boat and chair conformations.
Text section 3.11
1. A simple demonstration of like substances (e.g. alcohol and water, or any two water-soluble substances) mixing and of unlike substances separating (e.g. oil and water) after being mixed, is effective.
Text section 3.12
1. The functional groups are remembered best for their aromas. Obtaining samples of several and allowing students to smell them is usually effective and fun.
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