Changes of State
Science: Year 3 & 4 National Curriculum, topic 8.1.2
Changes of State
The state of a material is whether it is solid, liquid or gas. Changed of state are caused by changes in temperature.
Cooling liquids
- Cooling a liquid can turn it turn into a solid.
- Cooling water (liquid) enough will turn water into ice (solid).
- A liquid turns into a solid when it freezes.
Cooling gases
- Cooling a gas can turn it turn into a liquid.
- Cooling water vapour (gas) enough will turn water vapour into water (liquid).
- A gas turns into a liquid when it condenses.
Heating solids
- Heating a solid can turn it turn into a liquid.
- Heating ice (solid) enough will turn ice into water (liquid).
- A solid turns into a liquid when it melts.
Heating liquids
- Heating a liquid can turn it turn into a gas.
- Heating water (liquid) enough will turn water into water vapour (gas).
- A liquid turns into a gas when it evaporates.
The Temperatur of Changes of State
We can investigate the temperature that different materials change state.
Thermometers
- We can measure the change in temperature by using a thermometer.
- Thermometers measure the temperature scale in degrees Celsius (°C).
Ice melts and water freezes
- Ice (solid) melts and water (liquid) freezes at the same temperature.
- Ice melts to water when the temperature goes above 0°C.
- Water freezes to ice when the temperature goes below 0°C.
Water evaporates
- Water (liquid) evaporates to water vapour (gas) when the temperature goes above 100°C.
Water vapour condenses
- Water vapour (gas) condenses to water (liquid) when the temperature goes below 100°C.
Other materials
- Different materials have different melting and evaporating points.
Test yourself on Changes of State
What are the correct names for these changes of state?
What is it called when a liquid changes to a gas?
What is it called when a liquid changes to a solid?
What temperature does ice melt at?
Which of these is true about changes in state?