How gas pressure arises from collisions, the effect of temperature and volume, and how doing work on a gas raises its temperature. Includes Physics only content.
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1.How do the particles in a gas move?
Randomly, in all directions, with a range of different speeds.
2.What does the temperature of a gas relate to?
The average kinetic energy of its particles.
3.What happens to the average speed of particles as temperature rises?
It increases.
4.How does a gas exert pressure on the walls of its container?
The particles collide with the walls, and each collision exerts a small force. The pressure is the total force per unit area.
5.In which direction does gas pressure act?
At right angles to the surface, in all directions.
6.What happens to pressure if the temperature of a fixed volume of gas increases?
The pressure increases.
7.Explain why increasing temperature increases pressure.
The particles move faster, so they hit the walls more often and with greater force.
8.What happens to pressure if the volume of a gas is reduced at constant temperature?
The pressure increases.
9.Explain why reducing volume increases pressure.
The same number of particles are in a smaller space, so collisions with the walls happen more frequently.
10.State the relationship between pressure and volume at constant temperature.
pressure x volume = constant
11.A gas at 100 kPa occupies 2 m3. It is compressed to 1 m3 at the same temperature. Find the new pressure.
100 x 2 = 200. So new pressure = 200 divided by 1 = 200 kPa.
12.A gas at 300 kPa occupies 0.5 m3. It expands to 1.5 m3. Find the new pressure.
300 x 0.5 = 150. New pressure = 150 divided by 1.5 = 100 kPa.
13.What must be kept constant for the pressure volume relationship to hold?
The temperature and the mass of gas.
14.What does the graph of pressure against volume look like?
A curve, since pressure is inversely proportional to volume.
15.What does the graph of pressure against one over volume look like?
A straight line through the origin.
16.What happens to the internal energy of a gas when work is done on it?
It increases, so the temperature of the gas rises.
17.Why does a bicycle pump get warm when you use it?
Work is done on the gas as it is compressed, increasing its internal energy and raising its temperature.
18.What is meant by doing work on a gas?
Transferring energy to it by using a force to compress it.
19.Why does a gas cool when it expands rapidly?
The gas does work pushing against its surroundings, which reduces its internal energy.
20.Why is the pressure of the atmosphere lower at high altitude?
There is less air above, so fewer particles and fewer collisions per unit area.
21.Why does a sealed bag of crisps expand on a plane?
The air pressure outside falls, so the pressure inside is now greater and pushes the bag outwards.
22.Why must a gas be at constant temperature for the pV relationship?
Changing the temperature changes the speed of the particles, which changes the pressure independently of the volume.
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