It is a cold, clear day in January. Brrrrrr. Tomorrow is your best friend's birthday and you are in a store buying a bouquet of helium-filled balloons to decorate your friend's locker. You pay the lady at the counter and laugh at the brightly colored balloons.
[ Do not inhale the helium, it is dangerous. We here at Aspire once knew a guy who inhaled some helium. His head popped off. ]
You begin the walk home in the crisp, cold air. Again, Brrrrrr. As you finish the last block before you are home you notice something wrong with the balloons! They have shrunk! That lousy store, they sold you defective balloons! Arrrgh!
[ Hey! Calm down... We here at Aspire are here to help. :) ]
But before you demand your money back, let's figure out why this happened.
We'd better use an experiment that will help us to understand how pockets of gas behave when they are exposed to changes in temperature.
You should also be aware that we are only seeing a sliced-section of the
space inside the tube and not all the gas particles are visible. The tube
is closed off by a sliding plug.
[ We here at Aspire sometimes say "Cool Beans". ]
Scientists often test variables to find relationships. What variables were you testing in this lab? What changed? What stayed the same?
But wait- the fun isn't over yet. We still have some serious science to contemplate. How did your prediction match the data? Were you able to figure out what was going to happen?
Let's get back to the physics fun. Think about the experiment you just conducted. What happened when the temperature was raised? What happened when the temperature was lowered? In this experiment, what is the relationship between the temperature of a gas and the volume of the gas?
Is the relationship between temperature and volume direct or inverse?
Here's a little scientific information for you. All gases are made up of molecules or atoms (particles). Particles are always in motion, either zipping around like you have seen, or vibrating in place. The hotter a gas gets, the faster the particles move.
Now that you have some background knowledge, explain why increasing the temperature of a gas would cause the volume of the gas to increase. Explain why decreasing the temperature would decrease the volume of the gas. Now relate this to your helium balloon mystery. What may have caused the balloons to decrease in volume?
Scientists also use graphs to make predictions. Use your graph to
predict answers to the following questions:
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.
If a gas is kept at a constant pressure and the volume is 10 L with a temperature of 25 C, what will the volume of the gas be if we change the temperature to 35 C?
When you are done, click on check answer to see how you did.
Now try these questions:
That is quite the math workout. Congratulate yourself for your outstanding scientific abilities!