Friday, November 10, 2006

Got gas?

Chemistry class was so fun today! We have just started into Gas Laws and how different variables change the behavior of the gas. I had 8 stations set up around the room that the students rotated to. Here are the questions that the students had to answer:

1.What are the four Factors that effect a gas?
2.List the 2 variables that change at each station and explain what is happening to the gas.
3.Make a general statement relating each of the four factors at each station.
4.Tell whether each of the relationships in #3 is direct or inverse?

Before they could begin, they used the text to find the answer to #1 (pressure, volume, amount of gas and temperature). Then they rotated to the various stations to see how each variable affected another and recorded their observations.

One station consisted of a flask with balloon on top. The students placed the flask on a hotplate and then in ice water. On the hotplate, the balloon expanded, when it was placed in the cold water, it contracted. This shows that as temerature decreases, the volume of a gas decreases. We also used the vacuum pump, which the kids loved! I placed a marshmallow in the vacuum to show that as the pressure decreases, the volume increases. If you haven't seen a vacuum pump, it causes the marshmallow to grow and then shrivels up once the pressure inside the chamber is increased. (We have also use the "Peeps" during Easter season). The students soon wanted to put everything in the vacuum to see what would happen. We put the entire bag of marshmallows in to see how much they expanded, they built marshmallow castles to put in, a was fun!

On Monday we are going to use these demonstrations for the gas law calculations. This way they don't have to memorize 5 equations, they just have to know the relationship between the gas variables.

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