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fandomhigh2006-02-08 09:31 am
equalsmcsquared.livejournal.com) wrote in fandomhigh2006-02-08 09:31 am
Biology (2nd Period) / Chemistry (4th Period) / Forensics (5th Period)
"Good morning. Today we will be doing an experiment with photosynthesis. As you may, or may not remember, photosynthesis is the process by which plants convert sunlight and carbon dioxide into sugar, thus feeding the plant and expelling oxygen. Also of note--oxygen is necessary for breathing. Interesting fact, wouldn't you think?"
The experiment is listed on a packet Ms. Sidle is passing around.
"Good morning. As I said on Monday, today we will learn how to balance chemical equations."
Balancing Chemical Equations
Sometimes, however, we have to do some work before using the coefficients of the terms to represent the relative number of molecules of each compound. This is the case when the equations are not properly balanced. We will consider the following equation:
Al + Fe3O4---> Al2O3
Since no coefficients are in front of any of the terms, it is easy to assume that one (1) mole of Al and one (1) mole of Fe304 react to form one (1) mole of Al203. If this were the case, the reaction would be quite spectacular: an aluminum atom would appear out of nowhere, and two (2) iron atoms and one (1) oxygen atom would magically disappear. We know from the Law of Conservation of Mass (which states that matter can neither be created nor destroyed) that this simply cannot occur. We have to make sure that the number of atoms of each particular element in the reactants equals the number of atoms of that same element in the products. To do this we have to figure out the relative number of molecules of each term expressed by the term's coefficient.
Balancing a chemical equation is essentially done by trial and error. There are many different ways and systems of doing this, but for all methods, it is important to know how to count the number of atoms in an equation. For example we will look at the following term.
2Fe3O4
This term expresses two (2) molecules of Fe3O4. In each molecule of this substance there are three (3) Fe atoms. Therefore in two (2) molecules of the substance there must be six (6) Fe atoms. Similarly there are four (4) oxygen a toms in one (1) molecule of the substance so there must be eight (8) oxygen atoms in two (2) molecules.
Now let's try balancing the equation mentioned earlier:
Al + Fe3O4---> Al2O3+ Fe
Developing a strategy can be difficult, but here is one way of approaching a problem like this.
1) Count the number of each atom on the reactant and on the product side.
2) Determine a term to balance first. When looking at this problem it appears that the oxygen will be the most difficult to balance so we'll try to balance the oxygen first. The simplist way to balance the oxygen terms is:
Al +3 Fe3O4---> 4Al2O3+Fe
Be sure to notice that the subscript times the coefficient will give the number of atoms of that element. On the reactant side, we have a coefficient of three (3) multiplied by a subscript of four (4), giving 12 oxygen atoms. On the product side, we ha ve a coefficient of four (4) multiplied by a subscript of three (3), giving 12 oxygen atoms. Now, the oxygens are balanced.
3) Choose another term to balance. We'll choose iron, Fe. Since there are nine (9) iron atoms in the term in which the oxygen is balanced we add a nine (9) coefficient in front of the Fe. We now have:
Al +3 Fe3O4---> 4Al2O3+9Fe
4) Balance the last term. In this case, since we had eight (8) aluminum atoms on the product side we need to have eight (8) on the reactant side so we add an eight (8) in front of the Al term on the reactant side.
Now, we're done, and the balanced equation is:
8Al + 3Fe3O4 ---> 4Al2O3 + 9 Fe
"Good afternoon. Today we will begin a study into the forensic science behind investigating arson."
Arson investigation involves the study of fire-damaged physical evidence and crime scenes to detect arson. The techniques involved in such investigations require a basic grounding in the chemistry of explosives, the materials used in the formation of explosives as well as the various ways in which explosives are interrelated and initiated.
She lectures extensively on what arson entails.
Forensics
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She hesitates, "Plus... Crowley? Really scares me. And I don't know why and that scares me even more."
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She sighs. "Why is everyone so afraid of him? He doesn't scare Kiki or I... then again... he does go out of his way to scare others. I am so confused."
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She makes a little face, "Crowley... He just... I only ever saw him Saturday, but he just... terrified me. Bel, made me angry when he was singing, but he didn't scare me. Crowley..." she shuddered.
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Then a thought occurs to her. "Phoebe... would he try to do something to your friends to keep you? I'm not so worried for me, I'm not going anywhere near him, but Kiki... she... something bad happened to her last week and she's not quite herself yet. And she trusts him..."
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