3. Particle model of matter (internal energy and gas pressure)

Question 1

What is internal energy?

Answer 1

Where a system of particles will always store energy as long as the temperature is above absolute zero

Question 2

What 2 types of energy can internal energy be split into?

Answer 2

• Kinetic energy
• Potential energy

Question 3

What is the internal energy as a system?

Answer 3

The total kinetic energy and potential energy all the particles contain

Question 4

What is the process called when solids turn into liquids?

Answer 4

Melting

Question 5

What is the process called when liquids turn into gases?

Answer 5

Evapouration

Question 6

What is the process called when a liquid turns into a solid?

Answer 6

Freezing

Question 7

What is the process called when a solid turns into a gas?

Answer 7

Sublimating

Question 8

What is the process called when a gas turns into a liquid?

Answer 8

Condensing

Question 9

What happens when the internal energy of a system is changed?

Answer 9

A substance changes from one state to another

Question 10

What happens to the internal energy from a solid - liquid - gas?

Answer 10

There is an increase in the internal energy

Question 11

What happens to the internal energy from a gas - liquid - solid?

Answer 11

There is a decrease in the internal energy

Question 12

Describe what is happening in this graph

Answer 12

1. The substance is being heated up
2. The temperature remains constant until all of the substance melts
3. The liquid substance is being heated up
4. The temperature remains constant until all of the substance boils

Question 13

What is potential energy?

Answer 13

All the forces between the particles that make up a system

Question 14

How is potential energy in solids, liquids and gases?

Answer 14

• Solids: very strong
• Liquids: slightly weaker
• Gases: very weak

Question 15

What is a boiling point?

Answer 15

The temperature at which a pure substance boils or condenses

Question 16

What is a melting point?

Answer 16

The temperature at which a pure substance melts or freezes

Question 17

What is the equation for specific latent heat?

Answer 17

E = ML
Energy (j) = mass (kg) x specific latent heat (j/kg)

Question 18

What is specific latent heat of fusion?

Answer 18

The amount of energy required to melt 1kg of a solid into a liquid

Question 19

What happens when we heat a substance in terms of particles?

Answer 19

• When we heat a substance, the temperature increases
• So the particles gain more kinetic energy because they are moving/colliding with each other more

Question 20

What happens to the temperature when a substance changes state?

Answer 20

• The temperature stops increasing and stays constant
• Now the energy that we are putting in is weakening/breaking the forces of attraction between the particles

Question 21

What is the specific latent heat of a substance?

Answer 21

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

Question 22

What is the specific latent heat of vapourisation?

Answer 22

The energy required to change 1kg of a substance from a liquid to a vapour with no change in temperature

Question 23

Why is a change of state an example of a physical change?

Answer 23

-because no new substances are formed and the change can be easily reversed
- it’s the same substance as you started with, just in a different form
- because the particles are arranged differently

Question 24

Why is mass conserved during changes of state?

Answer 24

Because the number of particles doesn’t change, they are just arranged differently

Question 25

What causes gas pressure?

Answer 25

The pressure of a gas is due to particles colliding with the walls of the container that the gas is being held in

Question 26

What do the particles collisions cause?

Answer 26

• A force which creates right angles to the walls of the container
• The force acting over the area of the container causes gas pressure

Question 27

What happens if the gas is in a container with a bigger volume (and if temperature is constant)?

Answer 27

• then the pressure is reduced because the spacing between the particles has increased
• so particles travel much further before colliding with the walls of the container
• this reduces the number of collisions per second between the particles and the container, reducing the pressure

Question 28

What is the pressure of a gas inversely proportional to?

Answer 28

To the volume, if the volume increases than the pressure decreases

Question 29

What is the equation for pressure?

Answer 29

PV = constant
pressure (pa) x volume (m^3) = constant