3.1 CHANGES OF STATE AND PARTICLE MODEL

Question 1

What is the definition of density? State the relevant equation with units.

Answer 1

● The mass per unit volume of a material
● ⍴=m/v
● Density (kg/m3), Mass (kg), Volume (m3)

Question 2

State the different states of matter in order (least to most) of density of atoms.

Answer 2

● Least dense: Gas ● Liquid

● Most dense: Solid

Question 3

Describe the particle arrangement of a solid.

Answer 3

Tightly packed in a regular arrangement.

Particles can only vibrate on the spot.

Question 4

Describe the particle arrangement of a liquid.

Answer 4

Close together, but with an irregular arrangement. They can flow over each other.

Question 5

Describe the particle arrangement of a gas.

Answer 5

Separated, with no regular arrangement. Particles can move freely

Question 6

What is always conserved when a substance undergoes a change of state?

Answer 6

Mass

Question 7

How does a change of state differ from a chemical change?

Answer 7

In a change of state, the material can return to having its previous properties if the change is reversed.

Question 8

What is sublimation?

Answer 8

When a solid changes into a gas without passing through a liquid state.

Question 9

What is evaporation?

Answer 9

When a liquid changes into a gas state.

Question 10

What is is the opposite of evaporation?

Answer 10

Condensation, which is when a gas changes into a liquid state.

Question 11

When water boils in an open pan, why does the mass of the pan of water appear to decrease?

Answer 11

Some of the water will evaporate and turn into water vapour. This will leave the pan meaning the mass of the pan will decrease. The mass of the whole system however remains constant.

Question 12

Explain the processes involved when a bathroom mirror mists up.

Answer 12

● Hot water evaporates to form water vapour ● This water vapour lands on the cooler
mirror
● The vapour condenses and returns to liquid
state on the mirror’s surface