Summary
Changes of state involve the transformation of matter from one state to another, such as solid to liquid or liquid to gas.
- Melting — the process where a solid turns into a liquid. Example: Ice gains heat and melts at 0°C, known as the melting point.
- Freezing — the process where a liquid turns into a solid. Example: Water loses heat and freezes at 0°C, known as the freezing point.
- Condensation — the process where a gas turns into a liquid. Example: Water vapour touches a cooler surface, loses heat, and condenses into water droplets.
- Boiling — the process where a liquid turns into a gas at a specific temperature. Example: Water gains heat and boils at 100°C, known as the boiling point.
- Evaporation — the process where a liquid turns into a gas at any temperature. Example: Water gains heat and evaporates, with the rate affected by temperature, wind, and exposed surface area.
Exam Tips
Key Definitions to Remember
- Melting: Solid to liquid at melting point
- Freezing: Liquid to solid at freezing point
- Condensation: Gas to liquid
- Boiling: Liquid to gas at boiling point
- Evaporation: Liquid to gas at any temperature
Common Confusions
- Confusing boiling with evaporation; boiling occurs at a specific temperature, while evaporation can occur at any temperature.
- Misunderstanding that condensation requires a cooler surface.
Typical Exam Questions
- What is the melting point of ice? 0°C
- How does wind affect evaporation? Wind increases the rate of evaporation by carrying away water vapour.
- At what temperature does water boil? 100°C
What Examiners Usually Test
- Understanding of the processes of melting, freezing, boiling, and evaporation
- Factors affecting the rate of evaporation
- Differences between boiling and evaporation