14

Question 1

Describe the structure of particles in a gas.

Answer 1

Particles in a gas have almost no forces between them therefore they are completely free to move, and move at high speeds in random directions.

Question 2

Explain the pressure of a gas in terms of the motion of particles

Answer 2

The particles move in random directions. When they collide with the walls of a container they exert a force which acts at a right angle to the container. This causes pressure

Question 3

State the equation used to calculate pressure. Give appropriate units.

Answer 3

Pressure (Pa) = Force (N) / Area (m2)

P = F /A

Question 4

What factor affects the average kinetic energy of gas molecules?

Answer 4

The temperature of the gas
● The higher the temperature, the higher
the average kinetic energy of the molecules

Question 5

What effect does increasing temperature have on the pressure of a gas when held at constant volume?

Answer 5

Gas pressure will increase as the temperature increases.

Question 6

Why does pressure increase as temperature increases (at a constant volume)?

Answer 6

Kinetic energy of molecules increases
● Collisions between molecules becomes more frequent
● Greater rate of change of momentum
● Greater force and therefore pressure

Question 7

If gas A is at a low pressure, and gas B is at a high pressure, what can be said about the rate of collisions in each gas?

Answer 7

There are more collisions per second in gas B than in gas A

● The rate of collisions is higher in B

Question 8

Describe the force that the pressure of a gas exerts on the walls of its container.

Answer 8

● The net force acts at right-angles to each surface of the container
● The force increases as pressure increases

Question 9

Explain how increasing the volume of a gas results in a decrease of pressure.

Answer 9

● Molecules become more spread out so rate of collision decreases
● Rate of change of momentum decreases, and so force exerted on container decreases, resulting in a lower pressure

Question 10

What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?

Answer 10

Question 11

What is the unit used for pressure?

Answer 11

Pascal (Pa).

Question 12

What increases when you do work on a gas?

Answer 12

● The internal energy of the gas
● This can also lead to an increase of
temperature

Question 13

How do you convert between degree Celsius and Kelvin?

Answer 13

Question 14

What is absolute zero?

Answer 14

Particles have no kinetic energy and do not move.

−273 °C

Question 15

What equation can be used to calculate the pressure/volume for a gas for which the mass is fixed and temperature is constant?

Answer 15

Question 16

Why does the temperature of air inside a bike pump increase when it is pumped?

Answer 16

● Work is done on a gas when it is compressed ● Doing work on a gas increases its internal energy,
so increases the average kinetic energy of the
molecules
● Temperature increases with an increase of
average kinetic energy

Question 17

What is the definition of density? State the relevant equation with units.

Answer 17

Question 18

What is meant by a state of matter?

Answer 18

A form in which matter can exist, based on the particle arrangement in a substance.

Question 19

Give the different states of matter in order (least to most) of density of atoms.

Answer 19

● Least dense: Gas
● Liquid
● Most dense: Solid

Question 20

Use kinetic theory to explain the structure of liquids.

Answer 20

The particles have some kinetic energy. They are free to move and can move around in random directions at very slow speeds.

Question 21

Explain the movement of particles in a solid.

Answer 21

The particles vibrate around a fixed position as they do not have enough kinetic energy to move freely

Question 22

Describe the structure of particles in a gas.

Answer 22

Particles in a gas have almost no forces between them therefore they are completely free to move, and move at high speeds in random directions

Question 23

What is always conserved when a substance undergoes a change of state?

Answer 23

Mass

Question 24

How does a change of state differ from a chemical change?

Answer 24

In a change of state, the material can return to having its previous properties if the change is reversed

Question 25

What is the internal energy of a substance?

Answer 25

● The energy stored by the particles

● The sum of the total kinetic and potential energies that make up the system

Question 26

What two things can heating a substance do?

Answer 26

1. Raise its temperature

2. Change the state of the substance

Question 27

What three factors determine the temperature change of a system?

Answer 27

1. Mass of substance being heated
2. Type of material (Specific heat
   capacity)
3. Energy inputted into the system

Question 28

What is sublimation?

Answer 28

When a solid turns directly into a gas.

Question 29

What is the difference between physical changes and chemical changes in substances?

Answer 29

Physical changes can be reversed.

Chemical changes cannot be easily reversed.

Question 30

How does heating cause a substance to change state?

Answer 30

Heating matter gives particles more potential energy. This energy is used to break the bonds of
attraction, leading to a change of state.

Question 31

Why does heating increase the temperature of substance?

Answer 31

It increases the amount of thermal energy in that substance. It also gives the particles more kinetic energy, meaning they move faster and their temperature increases.

Question 32

State the equation used to calculate the energy change when a substance is heated. Give appropriate units.

Answer 32

Question 33

Define specific heat capacity.

Answer 33

The amount of energy needed to increase the temperature of 1kg of a substance by 1°C.

Question 34

Define specific latent heat.

Answer 34

The amount of energy needed to change the state of 1kg of a substance with no change in temperature.

Question 35

State the equation for the energy required to change state. Give appropriate units.

Answer 35