Physics 3 - Particle Model of Matter

Question 1

Density =

Answer 1

Mass divided by volume

Question 2

Solids

Answer 2

• strong forces of attraction hold particles close together in a fixed, regular arrangement
• particles don’t have much energy
• can only vibrate about their fixed positions
• highest density as particles are close together

Question 3

Liquids

Answer 3

• weaker forces of attraction between particles
• particles close together but can move past each other to form irregular arrangements
• have more energy than solid particles
• can move in random directions at low speeds
• less dense than solids

Question 4

Gases

Answer 4

• no forces of attraction between particles
• more energy than liquids + solids
• free to move
• move in random direction at high speed
• low density (less dense than liquids)

Question 5

Find density of a solid object

Answer 5

1. Use mass balance to find mass
2. Regular solid - find length, width + height (using ruler) and calculate volume
3. Irregular solid - can find volume by submerging into eureka can filled with water. Water displaced in measuring cyclones is the volume of the object
4. Use density formula to calculate density

Question 6

To find density of a liquid

Answer 6

1. Put measuring cylinder on balance and zero it
2. Pour 10ml into measuring cylinder + record liquid’s mass
3. Pour another 10ml into measuring cylinder, repeating process until cylinder is full + recording the total volume + mass each time
4. Use density formula to find density (1ml = 1cm^3)
5. Average calculated density to find value for density of liquid

Question 7

What is internal energy?

Answer 7

total energy that its particles have in their kinetic + potential energy stores

Ke = they vibrate + move around
P = their positions

Question 8

What happens to internal energy as a system is heated?

Answer 8

• heating system transfers energy to its particles (gain energy in kinetic energy stores + move faster), increasing internal energy
• change in temp or state

Question 9

What does the temperature change depend on?

Answer 9

• mass of substance
• it’s specific heat capacity
• energy input
  (Just rearranging specific heat capacity formula)

Question 10

How does a change in state occur? - when heated

Answer 10

If the substance is heated enough - particles will have enough energy in their kinetic energy stores to break the bonds holding them together

Question 11

Solid to liquid
Liquid to solid
Liquid to gas
Gas to liquid
Solid to gas

Answer 11

Solid to liquid = melting
Liquid to solid = freezing
Liquid to gas = boiling or evaporating
Gas to liquid = condensing
Solid to gas = sublimating

Question 12

Why is a change in state a physical change?

Answer 12

• don’t end up with a new substance - same substance as you stared with (different form)

Question 13

Why does a change in state conserve mass?

Answer 13

• number of particle doesn’t change - arranged differently
• mass is conserved (none of it is lost when substance changes state)

Question 14

What is latent heat?

Answer 14

Energy needed to change state of a substance

Question 15

Explain why a change of state from solid to liquid or liquid to gas requires energy + why the temperature doesn’t constantly increase?

Answer 15

When melting or boiling:
- putting in energy so increasing the internal energy
- but energy is used for breaking bonds between particles
-flat parts on graph - energy is being transferred by heating (not being used to change the temperature)

Question 16

Explain why a change of state from gas to liquid or liquid to solid requires energy + why the temperature doesn’t constantly dec rease?

Answer 16

When condensing or freezing:
- bonds are formed between particles
- releasing energy
- internal energy decreases but temp. doesn’t go down until all the substance has turned to liquid or solid
- flat parts on graph - energy transfer

Question 17

What is the specific latent heat of a substance?
FORMULA

Answer 17

Amount of energy needed to change 1kg of a substance from one state to another without changing the temperature

Energy = Mass x Specific Latent Heat
(J). (Kg). (J/kg)
E = mL

Question 18

Specific latent heat for changing between a solid and a liquid (melting or freezing) name

Answer 18

Specific latent heat of fusion

Question 19

Specific latent heat for changing between a liquid and a gas (evaporating, boiling or condensing) name

Answer 19

Specific latent heat of vaporisation

Question 20

What happens when you reverse a change of state?

Answer 20

• substance returns to its original form
• gets back its original properties