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It is often valuable to analyze data by graphing the variables.
Choose one of your experiments and make a graph of
volume versus temperature.
Usually the independent variable (the value you were able to select)
goes on the horizontal axis. The dependent variable goes on the vertical
axis. In this case, temperature will go on the X-axis
and volume (which depended on temperature) will go on the Y-axis.
Scientists also use graphs to make predictions. Use your graph to
predict answers to the following questions:
- If you heat a gas to 120 K what volume will the gas have?
- If you heat a gas to 73 K what volume will the gas have?
- Predict what the volume of the gas would be at 190 K and 440 K. These
numbers are not on the graph, but do the best you can.
For a challenge, look at another relationship found in your data.
(Do this section if your teacher gives the okay.)
Draw a third column on your data table and label it V/T. For each of the rows
in your data table divide the volume by the temperature and put that number in
the new column. Did you get the same number each time? Did your
neighbors get the same number each time? We call this number a constant.
Because V/T is always a constant, one set of volume and temperature numbers
will equal a second set of volume and temperature numbers:
V1 and T1 represent the first set of conditions and V2 and T2 represent the
second set of conditions.
This is only true if the numbers were collected at the same pressure. This
relationship is called Charles' Law.
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Practice a problem using the Charles' Law relationship:
If a gas is kept at a constant pressure and the volume is 10 L with a
temperature of 25 K, what will the volume of the gas be if we change the
temperature to 35 K?
When you are done, click on check answer to see how you did.
Now try these questions:
- If a gas with a volume of 15 L is at a temperature of 10 K, what is
the volume if the temperature changes to 30 K?
- If a gas with a volume of 25 L is at a temperature of 5 Kelvin,
what is the temperature if the volume has changed to 40 L?
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- If a gas with a volume of 19 L is at a temperature of 29 Kelvin,
what is the temperature if the volume has changed to 27 L?
- If you were to place your inflated balloon in the warm oven for a
few minutes, what would happen to it?
[ We here at Aspire do not
recommend eating your baked balloon. We here at Aspire think that is
icky. :) ]
- Why does a hot dog expand when it is heated over a fire? (It's
not really gases, but it's a similar process.)
- Okay, last question: why did your balloons deflate outside of the
store?
That is quite the math workout. Congratulate yourself for your outstanding
scientific abilities!
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