CP12

Question 1

What is the kinetic theory?

Answer 1

A theory that explains the properties of different states of matter in terms of the movement of particles. It states that everything is made of tiny particles.

Question 2

What does the kinetic theory say about particles in a solid?

Answer 2

In solids, forces of attraction hold particles closely together. The particles can vibrate but they cannot move around. This explains why solids keep their shape and usually cannot be compressed.

Question 3

What does the kinetic theory say about particles in a liquid?

Answer 3

In liquids, the particles are moving faster and so the forces of attraction between the particles are not strong enough to hold them in fixed positions. The particles can move past each other so liquids flow and take the shape of their container. The particles are still very close together, so liquids usually cannot be compressed.

Question 4

What does the kinetic theory say about particles in a gas?

Answer 4

In a gas, the particles are far apart and moving around quickly. Gases are compressible and expand to fill their container.

Question 5

What is the density of a substance?

Answer 5

The mass of a certain volume of the substance.

Question 6

How does the density of a substance vary when it is a solid and when it is a gas?

Answer 6

Almost all substances are most dense when they are solids and least dense when they are gases.

Question 7

How is density explained in terms of arrangement of particles?

Answer 7

A solid is usually denser than the same substance as a liquid, because the particles in solids are closer together.

Question 8

What is the equation for density?

Answer 8

density(kg/m³) = mass(kg) / volume(m³)

Question 9

What is the symbol equation for density?

Answer 9

p = m / v (p=Density, m=Mass, v=Volume)

Question 10

What is the formula triangle for density?

Answer 10

Mass
Density | Volume

Question 11

How can you work out the density of an irregular shaped object?

Answer 11

1.You need to devise an experiment involving: the object, a displacement can, measuring cylinder, a scale.
2. You need to measure the mass of the object
3. You need to get the displacement can and fill it with water until it reaches just below the nozzle
4. You need to put the nozzle of the displacement can over the measuring cylinder
5. Drop the object (the one you are measuring the density of) into the displacement can
6. Measure the amount of water that fell from the displacement can into the measuring cylinder (this is the volume of the object)
7. Use the mass obtained (by weighing the object) and the volume obtained (from the measuring cylinder) and input it into the density equation to find out the density

Question 12

What happens to the particles in a solid when it stores more thermal energy?

Answer 12

The particles of the solid vibrate more.

Question 13

What happens to the particles in a liquid and gas when it stores more thermal energy?

Answer 13

The particles of the liquid or gas increase the speed at which they move around.

Question 14

How can you maintain a store of thermal energy?

Answer 14

The store of thermal energy can be maintained by reducing the amount of energy that is transferred to the surroundings by heating.

Question 15

How can the amount of energy transferred to surroundings by heating be reduced?

Answer 15

This can be done by surrounding the warm object with insulating material (such as wool, foam or bubble wrap).

Question 16

What does the amount of thermal energy stored depend on?

Answer 16

-It’s temperature
- It’s mass
- The material that it is made from

Question 17

What is specific heat capacity?

Answer 17

The amount of energy it takes to increase the temperature of 1 kilogram of the substance by 1°c.

Question 18

What does a line increasing diagonally mean in a temperature, time graph (/)?

Answer 18

A diagonal line means that there is an increase in temperature and an increase in kinetic energy. Particles also vibrate more but there is no state change.

Question 19

What does a flat line mean in a temperature, time graph (-)?

Answer 19

A flat, straight line means that there is no increase in temperature and no increase in kinetic energy. Here the bonds are being broken and the substance is changing shape.

Question 20

What is specific latent heat?

Answer 20

The amount of energy it takes to make 1kg of a substance change state.

Question 21

What is the specific latent heat for fusion meant to be used for?

Answer 21

It is meant to be used for the processes of melting and freezing.

Question 22

What is the specific latent heat for vaporisation meant to be used for?

Answer 22

It is meant to be used for the processes of boiling and condensing.

Question 23

What is the formula for energy of state change?

Answer 23

Energy of state change(J) = Mass(Kg) x Specific latent heat(J/Kg)

Question 24

What is the symbol equation for energy of state change?

Answer 24

Q = m x L (Q=Energy of state change, m=Mass, L=Specific latent heat)

Question 25

What is the formula triangle for energy of state change?

Answer 25

Energy of state change
Mass | Specific latent heat

Question 26

What is the formula for change in energy?

Answer 26

Change in energy(J) = Mass(Kg) x Specific heat capacity(J/Kg°C) x Change in temperature(°C)

Question 27

What is the symbol equation for change in thermal energy?

Answer 27

△Q = m x c x θ (△Q=Energy, m=Mass, c=specific heat capacity, θ=temperature)

Question 28

How does the speed of particles in a substance affect its temperature?

Answer 28

The faster the average speed of the particles, the higher the temeprature.

Question 29

How does heating a gas affect the kinetic energy of its particles?

Answer 29

Heating a gas increases the kinetic energy of the particles, so they move faster and the temperature rises.

Question 30

Why does a gas have pressure?

Answer 30

The pressure of a gas is due to forces on the walls of a container caused by the moving particles hitting the walls. The faster the particles are moving, the more frequent their collisions will be and the more force they will exert when they collide.

Question 31

What effect does increasing the temperature of a gas have on the gas’ pressure?

Answer 31

Increasing the temperature of a gas increases the speed of the particles, so it also increases the pressure of the gas.

Question 32

What unit is pressure measured in?

Answer 32

Pascals (Pa), 1 Pa = 1 N/m²

Question 33

What is absolute zero?

Answer 33

The temperature at which the pressure of gas drops to zero. It is -273°c or 0k.

Question 34

What is the kelvin temperature scale?

Answer 34

A scale that measures temperature relative to absolute zero. The units are kelvin (K) and 1k is the same temperature interval as 1°c (so 1k would be -272°c). Absolute zero is 0k on this scale.

Question 35

How can you convert from celsius to kelvin and the other way around?

Answer 35

• To convert from Kelvin to Celsius, subtract 273.
• To convert from celsius to Kelvin, add 273.

Question 36

What is the average kinetic energy of the particles in a gas directly proportional to? (HINT: Involves absolute zero)

Answer 36

The average kinetic energy of the particles in a gas is directly proportional to the kelvin temperature of the gas (e.g. gas at 4k has an average kinetic energy of 4J).