Gas Laws – VTP Lab
Purpose:
The following activity will help you explore the relationships between the 3
properties of volume, temperature and pressure in their application of the Ideal
Gas Law, Boyle’s Law and Charles’s Law.
Background:
The pressure of the air (atmospheric pressure) changes all the time. Air pressure
can change due to changes in temperature and/or the density (which is related to
volume) of the air. As air pressure in the atmosphere changes so does the type of
weather we see.
To see how air and gases change we can look at the relationship between; the
volume a gas takes up, the temperature of the gas, and the amount of pressure on
the gas. We can predict what will happen to a gas if we know information about
the volume, temperature and/or pressure.
One statement of this relationship is called Boyle’s Law, in honor of Robert Boyle
who discovered it.
Boyle’s Law states that the volume of a gas decreases as its pressure increases, if
the temperature stays the same. Particles of a gas are pushed together when the
pressure is increased which results in a decrease in the volume (increased density).
If the pressure on a gas decreases the gas will expand. (Think opening a soda
bottle, opening the bottle reduces the pressure. A gas can be compressed into a
smaller space unlike a solid or a liquid.) Why?
Another statement of this relationship is called Charles’s Law, in honor of Jacques
Charles.
Charles’s Law states that the volume of a gas increases as its temperature
increases, if the pressure stays the same. Heating a gas causes it to expand. Gas
molecules gain more kinetic energy when heated and move faster (Hot air is less
dense (more spread out) than colder air which is denser).
All this stuff is hard to remember. To help you see the relationship between
volume, temperature & pressure you are going to make a Magic VTP Card.
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Procedure:
1. Get an index card.
2. Place it horizontally, and measure it. Divide it into thirds with 2 lines.
3. Use a hole punch and punch out a hole in the center of each section and label
it exactly as shown (see below).
4. Color it and make it look nice and beautiful.
5. Use this magic card to help answer the questions below (in your notebook).
6. Staple or tape the magic card in your notebook when done.
V
T
P
Volume
Temperature
Pressure
Conclusion: Answer the following in complete sentences.
*Copy down Boyle’s Law and Charles’s Law into your notebook.
Part A
1. Put your pencil through the temperature hole (middle hole) (that represents
holding temperature constant); rotate the card so pressure increases (goes
upwards). What happens to the volume when the pressure is increased?
2. What happens to the volume when the pressure is decreased?
3. What GAS LAW states this?
Part B
4. Place a pencil through the pressure hole indicating holding pressure
constant. What happens to the volume if you decrease the temperature?
5. What happens to the volume if you raise the temperature?
6. What GAS LAW states this?
Part C
7. Place a pencil through the volume hole. This indicates holding volume
constant. What happens to the pressure if you raise the temperature?
8. What happens to the pressure if you lower the temperature?
9. Why do you think gases can be compressed, but liquids and solids cannot?
10. Why is it extremely dangerous to put dry ice in a closed container? Use
your VTP card to explain this puzzle.
BONUS: What happens to the density of a gas if you increase the pressure?
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