P3

Question 1

States of matter

Answer 1

Solids: strong forces of attraction. Fixed, regular arrangement. Vibrate.
Liquids: weaker forces of attraction. Particles close together. Can move past each other & form irregular arrangement. Random direction.
Gases: almost no forces of attraction. Particles have more energy than liquid & solid. Free to move wherever.

Question 2

Collision theory

Answer 2

Particles in gases move around, bang into each other and the sides of the container, create energy.
Exert a force on what they collide with.
Pressure is the force exerted per unit area. So in sealed container, outward gas pressure is total force exerted by all particles on a unit area of the walls.

Question 3

Increase gas temp

Answer 3

Transfers energy to the kinetic energy stores of its particles. Temp of gas related to average energy in KE stores of the particles. Higher temp, higher average energy.
Increase temp of gas, and the average speed of its particles increases.
For a gas at a constant volume. Increasing temp increases pressure.

Question 4

Density

Answer 4

D=mass/volume
Kg/m cubed kg m cubed
Density of object depends on how particles are arranged and what it’s made of.
Dense=particles packed tight together
Compressing object moves its particles together making it more dense.

Question 5

Solid object practical

Answer 5

1. Measure mass with balance
2. Regular solid: measure length wide height with ruler and calc volume.
3. Irregular solid: find volume by submerging in eureka can full of water. Water displaced by object is transferred to measuring cylinder.
4. Record volume of measuring cylinder, thus is the volume.
5. Plug object Maas&volume into formula to find density.

Question 6

Liquid practical

Answer 6

1. Place measuring cylinder on a balance at 0
2. Pour 10ml liquid into measuring cylinder&record mass.
3. Pour another 10ml, repeat process.
   Record total vol + mass each time.
4. Each measurement, find density.
5. Take average of calculated densities, this will give value for density.

Question 7

Internal energy

Answer 7

• Internal energy of system =total energy its particles have in K&P stores.
• Heating a system transfers energy to particles. Increasing internal energy.
• Leads to change in temp/in state. If temp changes: size of change depends on mass of substance, what it’s made of(its SHC) & the energy input.
• Change in state occurs if substance is heated enough - particles have enough energy in KE stores to break bonds holding them together.

Question 8

Changes of state

Answer 8

Physical changes.
Freezing: liquid-solid
Melting: solid-liquid
Sublimating: solid-gas
Boiling/evaporating: liquid-gas
Condensing: gas-liquid 
Reverse change of state, substance returns to its original form&properties.
No. of particles doesn’t change - just arranged differently. Mass conserved.

Question 9

Specific Latent Heat

Answer 9

• amount of energy needed to change 1kg of it from one state to another without changing temp.
• For cooling, SLH is energy released by change in state.
• SLH diff for diff materials&changing between diff states.
• SLH of fusion: SLH for changing between solid&liquid.
• SLH of vaporisation: SLH for changing between liquid&gas.

Question 10

Specific latent heat equation

Answer 10

Energy (E) = mass (m) x specific latent heat (L)
E = J (joules)
M = kg
SLH = J/kg

Question 11

Changing state graphs: melting/boiling

Answer 11

Energy is put in substance when: melts/boils.
Increases internal energy.
Energy breaks intermolecular bonds rather than raising temp.
Flat spots on graph where energy is being transferred by heating but not being used to change temp.

Question 12

Changing state graphs: condensing & freezing

Answer 12

When substance condenses/freezes, bonds form between particles, releases energy. So internal E decreases, but temp doesn’t decrease until ALL substance condensed/froze.
Flat parts of graph show this energy transfer.