by Professor John Blamire
Wm.C.Brown, publisher
In this module, we will look at some of Chapter 7 together and learn how to identify the important principles, understand them, and then add the details.
Did you get all these points? If not, look over that page in the book again. Then make three headings in your notes; Forms of Energy, Laws, Energy and Life. You will now look at the chapter and identify the principles to put under these headings.
(1) For example, what is Organized Energy?... lets look. On page 85 we read that food and gasoline are forms of organized energy. If we look back at Chapter 4 we see that food molecules are (1) large, (2) polymers and (3) are very complicated. Their atoms are tightly held in huge, complex molecular arrangements in which smaller molecules (the monomers) are joined together in long strings or polymers. Gasoline is actually a mixture of hydrocarbons, which are the polymers found in things like fatty acids and lipids.
So food and gasoline are molecules in which the atoms are organized. into complex structures. Stored in the bonds holding these molecules together is the first form of energy; organized. energy.
But on page 85 another word is also used for this type of energy, that word is potential energy. The word potential means having the capacity to become something else, and comes from the Latin word potens, meaning powerful. So when this energy is called potential energy, it means that the energy is currently in a dormant, or stored form in the food molecules, but has the capacity or ability to be activated. It is also powerful energy.
This first type of energy, therefore has two properties; it is organized into the bonds of complex molecules, and it dormant right now, waiting to be released.
(2) Disorganized Energy. Back to page 85. This type of energy we learn, is the energy of motion. Objects on the move have this type of energy. All molecules above the coldest possible temperature (absolute zero) move around. Atoms in solids vibrate. Molecules in liquids dash around, but stay close enough to one another not to get separated too far. Molecules in gasses move even faster in all directions and move away from each other so their is even less attraction between them. All these atoms and molecules have disorganized energy of motion.
The word kinetic comes from a Greek word meaning motion, so kinetic energy is simply the energy seen in things that move. When things move around a lot, they become disorganized.
This second type of energy, therefore, has the two properties of being in motion and being all over the place, or disorganized.
(3) The First Law. This is very simple and self explanatory; in this universe there is a fixed amount of energy. You cannot make more of it, and you cannot get rid of any of it. All you can do is convert one form of energy into another form of energy. For example, turn on a flash light and the chemical energy stored in the battery is converted to electrical energy, which is converted to light and heat energy. At the end of the process, if you add up all the amounts of electrical, heat and light energy, they will be the same as the amount of chemical energy that was taken from the battery. The total amount of energy in the universe is still the same, even though we can now see in the dark.
In any natural process, therefore, you must always end up with the same amount of energy you started with.
(4) The Second Law of Thermodynamics. This is more tricky. Look at page 86. The publisher made a mistake when they printed Figure 7.3 (It was fine when I O.K.'d the proofs, so don't blame me!). But this figure shows an important point; in all natural processes, organized energy is always converted to disorganized energy. This principle is at the heart of the Second Law, which could be summarized by saying, things always run down, and things always get messier.
Take the flash light again. Before you turn it on, the energy in the battery is in a highly organized form in the chemicals between the positive and negative terminals. When you turn on the light, the chemical energy (actually differences in potential energy between electrons around ions), becomes energy of moving electrons, light energy and heat energy (as the air molecules move faster). When you turn the light off, the universe has less organized potential energy (the battery is weaker, and more run down), while the universe is messier (the air molecules are moving all over the place and light is zooming off into outer space).
Within a system (like the flashlight) the total of all energy conversions must always be in the direction of less organized energy (at the end of the process) and more disorder (also called higher entropy).
Now go back and fill in the rest of the details; how this chapter is going to use the di-saccharide sucrose to illustrate these and other principles, what is a calorie, and what is it used for?, what is entropy, what do living organisms do with the heat energy that is generated in these natural processes?
Read pages 86 and 87 and see if you can identify these key points.
Did you get these points? Once again, make headings in your notes. They should be; Chemical Reactions and Exchanging energy.
(1) Reactions that give off energy. On page 86 we read that a chemical reaction that gives off energy as it takes place is called exergonic. This word comes from exo- (meaning out) and the Greek word ergon meaning work.
If you light a candle a chemical reaction takes place in the flame. During this reaction oxygen gas is combined with the hydrocarbon wax molecules in the candle and the product molecules are carbon dioxide and water (vapor). Energy, in the form of light and heat are given off as this reaction takes place.
In living cells, food molecules (including hydrocarbons) are broken down and eventually carbon dioxide and water molecules are produced. Energy is also given off during these reactions. (See page 92).
Once the candle is alight, the flame continues to burn until it runs out of wax. Another word for these kinds of chemical reactions is spontaneous, since they take place, naturally, continuously and without any further external influence.
(2) Reactions that need energy. At the top of page 87 is an interesting observation; carbon dioxide molecules and water molecules in the air never rush together and re-form candles. (When was the last time you saw a candle suddenly appear from thin air?). Yet candles are made from carbon, hydrogen and oxygen.
Bees make wax, and humans make candles from that wax, but in the process both the humans and the bees put a lot of energy into the candle making process. A lot of energy (heat, bees buzzing about) is needed before candles can be made.
Plants, animals (including bees) do make wax however. Wax making is a synthetic process in which smaller units (molecules) are joined together to make larger units. In order to make the wax, plants and bees must first find a source of energy (such as food) and use some of the energy in the food to make the wax. Without the input of this energy from somewhere else, the wax will never get made. Such reactions are nonspontaneous and do not take place naturally or continuously unless there is external assistance.
(3) The diagrams make it clear. Look at figures 7.4 and 7.5 on pages 86 and 87. All molecules carry around with them a certain level of potential energy (remember what that is, or look back above). Wax and oxygen molecules have a lot of stored, potential energy. (Fig. 7.4). Carbon dioxide and water molecules have a lot less potential energy. During a chemical reaction that goes from wax and oxygen to carbon dioxide and water, you are going from molecules with a lot of stored energy to molecules with a lot less stored energy.
From the first law of thermodynamics we know that the total amount of energy at the end of the reaction must be the same as at the start of the reaction... so... the difference in energy between the starting molecules and the end molecules must go somewhere. That somewhere is the light and heat that is given off in the flame of the candle. If we take the energy in the wax and oxygen molecules at the beginning, and add up the sum of the energies in the carbon dioxide, water, light and heat at the end of the reaction, the two sets of numbers must come out the same. This is true for all spontaneous, exergonic chemical reactions, inside or outside cells.
(4) Now look at Figure 7.5. Imagine that the molecules on the left are once again the carbon dioxide and water. They are at low levels of potential energy. The molecule on the right is the candle wax (a long chain hydrocarbon), that is high in potential energy. Before the bee can make the wax it must obtain in the difference in energy between these sets of molecules from somewhere else and add that energy to the reacting molecules before they can become wax.
(5) Making the Link. Cells carry out both kinds of reactions (see the bottom of page 87). In some reactions (such as the breakdown of food molecules), energy is given off. Other reactions (like the bees making wax) require energy. The bees take some of the energy given off as they break down the food and use it in the processes that need energy, like making wax.
Read the last two sentences on page 87, see if they now make sense.
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