Chem Std. Blog Post

Chem Std. 9a: Students know how to use Le Chatelier's principle to predict the effect of changes in concentration, temperature, and pressure.

What is Le Chatelier's Principle?

• If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.

Soo basically, Le Chatelier's Principle says that if you change the condition of an equation's equillibrium....the equation will compensate by shifting to the left or to the right to maintain its equillibrium. You can affect a reaction by changing its pressure, temperature, or concentration.

Changes in Concentration:

• Using Le Chatelier's Principle, we know that the position of equilibrium will move to counteract the changes made in concentration.If the concentration of A is increased, the position of equilibrium will move to the right so the concentration of A decreases again. But if the concentration of A is decreased, then the equilibrium shifts to the left to replace what it has lost.

Changes in Temperature:

• For this type of reaction, you need to know whether the heat is being absorbed or let out. If the heat of reaction is a part of the product and less than zero, then the reaction is exothermic. If the heat of reaction is a part of the reactants and greater than zero, then the reaction is endothermic. When temperature is increased or decreased, the equilibrium will shift to whichever side has less heat so it may balance out the reaction.

Changes in Pressure:

• In this reaction, when you increase pressure the equilibrium will shift towards the side with the least amount of molecules. However, a decrease in pressure results in a shift towards the side with more molecules in order to increase the pressure overall.

C(s) + H2O(g) <--> CO(g) + H2(g)

If you increase the pressure, the equilibrium will shift towards the left. There is one gas particle on the left but there are two on the right....this means that when you increase pressure, the equilibrium will shift towards the side with less gas particles (the left).

As you can see, Le Chatelier is a man of balance. Without him, out reactions would be a mess.

IProposeWe Make Hydrogen Bubbles

Links:

• How to Make Hydrogen Bubbles
• More Hydrogen Experiments

Materials: Test Tube, Vinegar, Long Iron Nail, Sand Paper

Procedure:

1. Pour about one inch of vinegar into your test tube then secure the test tube on a rack.
2. Using your sandpaper, sand the tip of the nail.
3. Place the nail into the vinegar with the sanded side down.

Safety Precautions:

• Do not use the sand paper against the surface of your skin.
• Keep the iron nail away from your face.

Scientific Principles:

• Vinegar is an acetate acid that reacts with iron.
• The vinegar dissolves the iron into the solution releasing hydrogen.

David Webb

So David Webb came to our class and gave a pretty cool presentation on pressure. He showed us examples of different units to measure pressure then showed us what different things pressure can do to an object. One of the most interesting examples he showed us was one about a balloon. He set a regular balloon in a sealed vacuum chamber and slowly the balloon just got bigger. It made no sense to me really but after a minute or two, the balloon was twice its size! It was crazy! Other than that, David Webb did other experiments using pressure. In the end, it was a very interesting presentation. One example he gave us that I myself tried was the one about filling a cup up with water then using a card, placing it on top of the cup, then flipping it over and watching the cup filled with water just keep the water there. I was successful :D

Wicked

This month or next month I'm planning to go see the play Wicked. I can't wait!!! I'm so excited because Wicked is such an AMAZING play. The girl's voice is beautiful. Can you imagine waking up everyday to go to work and paint yourself green? She has such talent and it's people like her that make me wonder how long it takes to become that good at something. My brother is planning to take me to San Francisco to see it along with my aunt and mom. I literally am so excited to go watch it. Just seeing the preview for it on youtube made me jump out of my seat! Can't wait!

SMILE :]

The play SMILE is tonight! It started on Thursday so now there will be another one tonight and tomorrow and even Sunday. From what I heard, Mills is hosting this play about beauty pageants and such things. Personally, these types of plays aren't much of an interest to me but I get extra credit to go :] My friends that went last night said it was pretty interesting to watch so I guess I'll go with an open mind. The only issue I have is I'd rather be going to watch a big broadway play instead. Oh well, one day my classmates may be on broadway so I better go watch them now! What the future holds, the world may never know....

Crushing Cans

The lab we did to test pressure on cans was surprisingly really fun. The only problem is that I've already done things like that before. In Taylor Middle School, during open house, I was assigned to help during our science class experiment. So I was the one to boil the water in the soda cans. Since I had already seen this experiment it was just all the more fun to do it a second time. The only problem was that people got out of hands with the water and started playing around a little too much. Either way, I still learned that the when the can goes from high temperature to low temp with water in side, it crushes!

Chemical Reactions

This unit was really boring to me but I found the labs to be fun. Chemical reactions are kind of cool but only when you're working hands on. The temperature lab was actually a little interesting but overall the entire equilibrium packet bored me. Especially since my chemistry class is turning into more of a math class than my precal class. It not only stresses me out but it makes my poor little self angry :( Chemicals are cool...chemical reactions are not. But I suppose you've got to learn how to walk before you can run.

Stoichiometry Isn't That Bad

Chemistry is a world full of confusion and frustration. There are math equations, physics equations, and maybe even general knowledge that you never wanted to know. For the most part, I've hated chemistry because of the confusion but I always loved labs involving different solutions. Naturally when I heard about stoichiometry, I just whined and said, "Another way of making my head hurt." But to much of my surprise, I actually really like stoichiometry! It's so much easier than anything else we've learned. Once you get the hang of it, all is good. I'm so happy that this is the stuff we're studying for the next few weeks :D Here's the base of how to convert anything. It doesn't apply to stoichiometry directly but it does show how to convert.