When a solid absorbs heat, its particles vibrate faster and begin to slide past each other, turning into a liquid.
Example: Ice melting into water.
Exam tip: The word melting comes from the idea of a solid “melting” into a liquid.
When a liquid loses heat, its particles slow down and arrange into a fixed structure, becoming a solid.
Example: Water turning into ice.
Exam tip: Freezing is the opposite of melting.
At any temperature, molecules at the surface of a liquid can escape into the air, becoming gas.
Example: Water evaporating from a puddle.
Exam tip: Evaporation is a surface process; it happens only at the liquid’s surface.
When gas cools, its particles lose energy and come together to form liquid droplets.
Example: Dew on grass in the morning.
Exam tip: Condensation is the reverse of evaporation.
| Process | Change | Example |
|---|---|---|
| Melting | Solid → Liquid | Ice → Water |
| Freezing | Liquid → Solid | Water → Ice |
| Evaporation | Liquid → Gas | Water puddle → Vapor |
| Condensation | Gas → Liquid | Steam → Water droplets |
• Melting is like a chocolate bar turning into a liquid when you hold it in your hand.
• Freezing is like a puddle of water turning into a solid ice cube in a freezer.
• Evaporation is like the steam that rises from a hot cup of tea.
• Condensation is like the water droplets that form on the outside of a cold soda can.