Lesson 4: States of Matter and Temperature
Heating and cooling can change a substance from one state to another. Melting, freezing, and evaporation introduce changes of state, alongside the difference between these changes and changes such as burning.
Key Ideas
- All matter has mass and takes up space.
- Heating or cooling can change a material from one state to another, such as ice melting into water.
- Different materials melt and boil at different temperatures.
- Some changes can be undone, such as melting and freezing water. Burning paper makes new substances and cannot be undone simply by cooling it.
- Heat is energy moving from warmer things to cooler things. It can warm a material or help change its state.
Vocabulary
- States of Matter: Three common states: solid, liquid, and gas.
- Melting: A solid changes into a liquid.
- Freezing: A liquid changes into a solid.
- Evaporation / Condensation: Evaporation is liquid changing into gas at its surface. Condensation is gas changing into liquid.
- Reversible Change: A change that can be undone, such as melting water and freezing it again.
- Nonreversible Change: A change we cannot easily undo, such as burning paper.
Discussion Questions
- If heat causes things to melt, why does the sun not melt rocks on Earth?
- Water is unusual because it expands when it freezes instead of shrinking like most substances. Why do you think this matters for life on Earth?
- Is there a temperature at which everything in the universe would be a gas? Is there a temperature at which everything would be a solid?
Digging Deeper Topic
What is Plasma? Why do you think we don't go over it in this lesson? Recommend this video from Teded