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.
• ρ = 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 irregular arrangement.

- They can flow over each other.

Question 5

Describe the particle arrangement of a gas

Answer 5

• Separated, with no 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 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 vapor. 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 vapor.
• This water vapor lands on the cooler mirror.
• The vapor condenses and return to liquid state on the mirror’s surface.