Changes of state and the particle mode (3.1) (M)

Question 1

Describe the properties of solids

Answer 1

• fixed volume (in fixed columns - particles vibrate)
• fixed shape
• cannot be squashed
• highest density (with a few exceptions like water and ice)

Question 2

Describe the properties of liquids

Answer 2

• fixed volume
• no fixed shape - take up shape of container
• cannot be squashed
• relatively high density (but lower than solids)

Question 3

Describe the properties of gases

Answer 3

• no fixed volume
• no fixed shape - taker up shape of entire container
• can be squashed/compressed
• low(est) density - liquids/solids much more dense than this

Question 4

What is sublimation?

Answer 4

the change of state from gas to solid and vice-versa, bypassing the liquid state

Question 4

When substances change state mass is (…)

Answer 4

conserved

number of particles do not change, just the spacing and arrangement of the,

Question 5

changes of state are (…) changes

Answer 5

physical - note chemical

Question 6

How do physical changes (e.g. changes of state) differ from chemical changes

Answer 6

because the material recovers its original properties if the change is reversed

Question 7

When particles are heated, their size (…). Why?

Answer 7

increases/expands as particles are vibrating and thus moving

e.g. why metal ball will not fit through metal ring when heated

Question 8

When particles are heated, what happens to their density?

Answer 8

it decreases

Question 9

Particles with a lower density will (…) in the air

Answer 9

rise

Question 10

Describe how a convection current in a smoke chamber (gas convection) could occur as a flame is placed inside?

Answer 10

The flame will heat the gas particles above it, decreasing their density and causing them to rise out of the chimney, therefore the gap will be filled with particles from the cold air, which are then heated as the process repeats

Question 11

4 marker

Why does one kilogram of gas have a much greater volume than one kilogram of solid?

Answer 11

there are strong forces of attraction in the solid

which holds the particles close together / in a fixed pattern

but in gases, the forces between particles are negligible

so the particles are further apart

Question 12

When air is cooled, the energy of the air particles (…)

The spaces between the air particles are (…)

The density of the air (…)

Answer 12

decreases

decreases

increases

Question 13

4 marks

The fridge has a freezer compartment, which is colder than the rest of the fridge

Why does the air inside a fridge form a convection current when the fridge door is closed?

Answer 13

• air near freezer compartment is cooled
• cool air is (more) dense
• so (cooler) air falls
• air at bottom rises