Changes of State and Particle Model

What is the definition of density?

The mass per unit volume of a material

State the relevant equation for density with units

Density (kg/m³) = Mass (kg) ÷ Volume (m³

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

• Least dense: Gas

• Liquid

• Most dense: Solid

Describe the particle arrangement of a solid

Tightly packed in a regular arrangement. Particles can only vibrate on the spot

Describe the particle arrangement of a liquid

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

Describe the particle arrangement of a gas

Separated, with no regular arrangement. Particles can move freely

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

Mass

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

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

What is sublimation?

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

What is evaporation?

When a liquid changes into a gas state

What is the opposite of evaporation

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

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

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

Explain the processes involved when a bathroom mirror mists up

• 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