P3 Particle Model

Question 1

describe internal energy

Answer 1

• internal energy is stored by the particles that make up a system
• the particles in a system vibrate or move around because they have energy in their potential energy stores
• the energy stored in a system is stored by particles. the internal energy of a system is stored by its particles. the internal energy of a system is the total energy that its particles have in their kinetic and potential energy stores
• heating the system transfers energy to its particles increasing the internal energy
• this leads to a change in temperature or a change in state. if the temperature changes the size of a change depends on the mass of the substance.
• a change in state occurs if the substance is heated enough, the particles will have enough energy in their kinetic energy stores to break the bonds holding them together

Question 2

what happens when a substance is melting or boiling

Answer 2

you are putting in energy and so increasing the internal energy however the energy is used for breaking bonds between particles rather than raising the temperature. there are flat spots on the heating graph where energy is being transferred by heating but not being used to change the temperature

Question 3

when happens when a substance is melting or freezing

Answer 3

bonds are forming between particles which releases energy. this means that the internal energy decreases but the temperature does not go down until all of the substance has turned into a liquid or a solid. the flat parts of the graph show this energy transfer

Question 4

what is specific latent heat

Answer 4

the amount of energy needed to change 1kg of something from one state to another without changing its temperature.

Question 5

what is the specific latent heat for changing between a solid and a liquid

Answer 5

specific latent heat of fusion

Question 6

what is the specific latent heat for changing between a liquid and a gas

Answer 6

specific latent heat of vaporisation

Question 7

what happens when gas particles collide

Answer 7

as gas particles move about at high speeds they bang into each other when they collide they exert a force onto it. in a sealed container the outward gas pressure is the total force exerted by all of the particles in the gas on a unit area of the container walls.

Question 8

what relationship do pressure and volume have

Answer 8

they are inversely proportional

Question 9

what happens when there is a change in pressure

Answer 9

there can also be a change in volume

Question 10

what happens when you do work on a gas

Answer 10

the internal energy increases, which also increases the temperature