What You Need to Know

Key Concept Diagram

Solid: particles are closely packed in a regular structure, vibrating in fixed positions

Liquid: particles are close together but can move past each other; liquids take the shape of their container

Gas: particles are far apart and move rapidly in all directions; gases fill their container

Changes of state: melting, freezing, evaporation (vaporisation), condensation, sublimation

During a change of state, temperature remains constant as energy is used to break/form bonds

Key Vocabulary

State of Matter

One of the physical forms in which matter exists: solid, liquid, or gas (also plasma)

Melting Point

The temperature at which a substance changes from solid to liquid

Evaporation

The change from liquid to gas that can occur at the surface of a liquid below boiling point

Sublimation

A change of state directly from solid to gas without passing through the liquid state (e.g. dry ice)

Knowledge Check

Select the correct answer for each question. Click "Check Answer" to see if you are right.

Question 1

Which statement correctly describes particles in a gas?

They are arranged in a fixed, regular pattern They are close together but can slide past each other They are held in place and only vibrate They are far apart and move rapidly and randomly in all directions

Question 2

Water is heated from 20 degrees C to 110 degrees C. At 100 degrees C, the temperature stops rising briefly. Why?

Energy is being used to break intermolecular bonds during the change of state (boiling) The water runs out of energy The thermometer is broken Water cannot absorb more heat at that temperature

Question 3

Dry ice (solid CO2) goes directly from solid to gas without melting. This process is called:

Evaporation Sublimation Condensation Deposition

States of Matter