Pressure, Volume, Gases

Question 1

If you increase the temperature of a gas, what energy stores is energy being transferred to

Answer 1

If you increase the temperature of a gas, you transfer energy into the kinetic energy stores of its particles

Question 2

The higher the temperature, the higher the _____ energy in the kinetic energy stores of the particles in a gas

Answer 2

The higher the temperature, the higher the average energy in the kinetic energy stores of the particles in a gas

Question 3

How do gases produce pressure

Answer 3

The particles in a gas move randomly (they can move in any direction upto a maximum speed)

When gas particles collide with an object they produce a force.

This force is acting over a given area.

Since Pressure (p) = Force/Area, the gas produces pressure

Question 4

Describe the relationship between temperature and pressure

Answer 4

If a gas in a container is heated, the particles gain kinetic energy
Therefore the particles will have a greater velocity

Therefore when the particles collide with the container they produce a greater force

There are also more collisions occurring producing a greater force
p=F/A. If force increases, pressure increases

Question 5

Describe the relationship between pressure and volume

Answer 5

If a gas in a container is compressed:

The particles will be closer together therefore there will be more frequent collisions between the particles and the walls of the container causing a greater (average) force on the walls of the container

The area of the container will also decrease when compression occurs.

p=F/A. Area has decreased, force has increased therefore pressure will increase

Question 6

In what direction does the force of the particle collisions at in

Answer 6

The particle collisions cause a force which acts at right angles to the walls of the gas container (or any surface).

Question 7

How can pressure cause the gas to be compressed or expanded

Answer 7

The pressure of a gas causes a net outwards force at right angles to the surface of its container

There is also a force on the outside of the container due to the pressure of the gas around it.

If a container can easily change its size, then any change in these pressures will cause the container to compress or expand, due to the overall force

Question 8

Complete the sentence
If the volume is constant, the increasing the temperature of the particles will increase the ___ of the particles, and so the ___________

Answer 8

If the volume is constant, the increasing the temperature of the particles will increase the speed of the particles, and so the pressure

Question 9

Explain how increasing the temperature of a gas increase the average speed of the particles

Answer 9

If the temperature of a gas is increased, energy is transferred to the kinetic energy stores of its particles.

The temperature of a gas is related to the average energy in the kinetic energy stores of the particles in the gas. The higher the temperature, the higher the average energy

Therefore, by increasing the temperature of a gas, the average speed of the particles increase

Question 10

Complete the sentence
Changing the temperature of a gas, held at constant _______, changes the pressure exerted by the gas.

Answer 10

Complete the sentence
Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas.

Question 11

How does
increasing the volume in which a gas is contained, at constant
temperature, can lead to a decrease in pressure.

Answer 11

By incresing the volume in which a gas is contained, the spacing between the particles has increased

Particles now travel much further before colliding with the walls of the container.

This reduces the number of collisions per second between the particles and the walls of the container, reducing the pressure

Question 12

What is the pressure of a gas inversely proportional to

Answer 12

The pressure of a gas is inversely proportional to the volume

Question 13

State Boyle’s law

Answer 13

For a fixed mass of gas at a constant temperature, pressure is inversely proportional to it’s volume

pressure x volume = constant

Question 14

State the equation that links pressure, volume and constant
in words, symbols with units

Answer 14

pressure x volume = constant
pV = constant

pressure, p, in pascals, Pa
volume, V, in metres cubed, m3

Question 15

Describe the method to the experiment that proves Boyle’s law

Answer 15

1) Air is pumped into the apparatus which increases the pressure. The pressure acts on the air column reducing its volume
2) The length of the air column, l, will indicate the volume of the air

Question 16

Show using numbers how pressure x volume = a constant

Answer 16

pressure x volume = constant
100 x 5 = 500

(÷2 ) (x2)
50 x 10 = 500

Question 17

What is another way of writing pressure x volume = constant

Answer 17

p1 x V1 = p2 X V2
(all the numbers are subscript)

Question 18

Draw and label the experiment which proves Boyle’s law

Answer 18

file:///C:/Users/44748/Documents/Boyle’s%20law.pdf

Question 19

Explain why the length of the air column is measured rather than the volume

Answer 19

Volume = cross section x height (height is the length)
Volume = length x πr5^2
If the volume decreased, the length decreased. This is because the radius is constant.

Question 20

Using this data plot a graph then use it to prove Boyle’s law

Pressure Length of the
air column (in
cm)

15 32.0
18 27.0
23 21.0
28 16.5
34 14.0
37 12.7
40 11.8
43 11

Conclusion: What does this graph prove

Answer 20

file:///C:/Users/44748/Documents/Boyle’s%20law.pdf

Question 21

Draw the graphs that could represent the relationship between pressure and volume (for a fixed mass of gas at a constant temperature)

Answer 21

file:///C:/Users/44748/Documents/Boyle’s%20law.pdf

Question 22

Complete the sentence
For a fixed _______ of gas at a constant _________, the pressure of a gas increases as the __________ of its container decreases.

Answer 22

Complete the sentence
For a fixed mass of gas at a constant temperature , the pressure of a gas increases as the volume of its container decreases.

Question 23

State What doing work on a gas can increase increase

Answer 23

Doing work on a gas increases the internal energy of the gas and can cause an increase in the temperature of the gas.

Question 24

Describe the effect of doing work on an enclosed gas e.g. on a bicycle pump.

Answer 24

Work is the transfer of energy by applying a force.
Doing work on a gas, transfers energy to the kinetic energy stores of the gas particles, increasing the internal energy which increases the temperature.

Question 25

What would happen if the compression of a gas did not happen slowly - why wouldn’t this be the case if the gas was compressed slowly

Answer 25

If a gas is compressed rapidly, the work done on a gas would increase its internal energy store and its temperature as the work done on it and energy is transferred quickly enough to its surroundings.

By compressing the gas slowly, the gas loses energy by heating its surroundings at the same rate as energy is transferred into it. So the internal energy store and the temperature of the gas does not change

Question 26

What would happen if the compression of a gas happened slowly

Answer 26

By compressing the gas slowly, the gas loses energy by heating its surroundings at the same rate as energy is transferred into it. So the internal energy store and the temperature of the gas does not change

Question 27

What happens when particles in a system are heated in terms of their internal energy

Answer 27

When particles in a system are heated, the kinetic energy store of the particles increase, causing an increase in the internal energy of the particles. This either raises the temperature of the system or produces a change of state