4. What is gas?
Gas - a substance that is characterised by:
• widely separated molecules in rapid motion
• No definite shape/volume
– Expands to fill its container
• Easily compressed (squeezed into a smaller
container)
– Compressibility is a measure of how much the volume
of matter decreases under pressure
– Gases are easily compressed because of the space
between the particles in a gas
5. Common gases include - O2 and N2, the major
components of "air"
Other common gases - F2, Cl2, H2, He, and
N2O (laughing gas)
6. 4 things
You can predict the behavior of gases
based on the following properties:
pressure, P, Pascal's
volume, V, litters.
temperature, T, Kelvin's.
number of particles, n, moles.
7. 1- Pressure and the number of
molecules
Pressure and the number of molecules are
directly related:
More molecules means more
collisions.
Fewer molecules means fewer
collisions.
8. 1- Pressure and the number of
molecules
If you double the
number of molecules,
You double the
pressure.
As you remove
molecules from a
container the pressure
decreases Until the
pressure inside equals
the pressure outside
Molecules naturally
move from high to low
9. The diagrams below show a sealed container at three pressures.
Complete the labels showing the gas pressure in each container.
What can happen if too much air is pumped into a tire?
10. 2-Changing the size of the container
In a smaller container:
Molecules have less room to move.
Hit the sides of the container more often.
As volume decreases pressure increases.
11. 2-Changing the size of the container
As the pressure on
a gas increases the
volume decreases.
Pressure and volume
are inversely related.
pressure
volume
12. In the diagram,
complete the labels
showing the pressure
on the piston and the
gas pressure inside the
container.
When the volume is
reduced by one half,
what happens to the
pressure?
…………………………
…………………………
………………
13. 3- Temperature
Raising the temperature
of a gas increases the
pressure if the volume is
held constant. … why?
The molecules hit the walls
harder.
14. 3- Temperature
Raising the temperature
of a gas increases the if
the volume pressure is
held constant.
15. Work sheet
Work instructions
Complete this work sheet.
You are going to work in 4 teams of 3 students each.
Your answer must be in cloze in this words : {direct
– inverse- increase – decrease}
you can use a word more than one.
We have 10 minutes to run the activity.
16. Work sheet
1. If the temperature is constant, the relationship
between pressure and volume is……….
2. If the pressure is constant, the relationship between
temperature and volume is…………..
3. pressure of gas increased and its volume remains
constant, its temperature will …………………
4. If a gas volume is decreased and pressure, its
temperature will …………………
5. If the temperature of a gas remains constant but
pressure is decreased, the volume will…………
6. Raising the temperature of an enclosed gas causes its
pressure to ……………
7. If too much air is pumped into a tire the pressure will
………….
17. Explain why it is dangerous to throw
aerosol cans into a fire.
