Basic 3 · Science · Materials
Changing State
In this topic you will learn how substances change between solid, liquid and gas.
By the end of these notes you should be able to:
- Explain melting and freezing
- Explain evaporation and condensation
- Give everyday examples of changes of state
What you already know
- Solids, liquids and gases (Basic 2)
Copy everything that has a blue line on its left into your notebook. The other parts are for reading.
- Strand
- Diversity Of Matter
- Sub-strand
- Materials
- Indicator
- B3.1.2.3.1 – Explain how substances change state between solid liquid and gas
Introduction
Put shea butter in a metal cup in the sun. It melts into a liquid. When it cools, it becomes solid again. This is a change of state.
1. Four Changes of State
| Change | From → To | Example |
|---|---|---|
| melting | solid → liquid | ice melts; shea butter melts in the sun |
| freezing | liquid → solid | water in a freezer becomes ice |
| evaporation | liquid → gas | wet clothes dry in the sun |
| condensation | gas → liquid | water drops form on a cold bottle |
2. Heat Makes the Change
- Adding heat: melting and evaporation.
- Taking away heat (cooling): freezing and condensation.
Safety: Only heat things with your teacher. Hot liquids can burn.
New words
- melting
- Changing from solid to liquid.
- freezing
- Changing from liquid to solid.
- evaporation
- Changing from liquid to gas.
- condensation
- Changing from gas to liquid.
Summary
- Substances can change between solid, liquid and gas.
- Heating causes melting and evaporation.
- Cooling causes freezing and condensation.
Class activity: Melt and Set
- Put shea butter in a metal cup in the sun.
- Watch it melt.
- Move it to the shade and watch it become solid again.
You need: Shea butter in a metal cup, Bowl of teacher-provided warm water, Printed reversible-change picture cards
Exercises
Answer in your exercise book first, then check your answers.
1. Ice changing to water is…
- A. Melting
- B. Freezing
- C. Evaporation
- D. Condensation
Show answer
Answer: MeltingSolid to liquid.2. Wet clothes dry in the sun because of…
- A. Evaporation
- B. Freezing
- C. Melting
- D. Condensation
Show answer
Answer: EvaporationWater turns to gas.3. Freezing changes a liquid into a solid.
- A. True
- B. False
Show answer
Answer: TrueWater becomes ice.4. Condensation changes a liquid into a gas.
- A. True
- B. False
Show answer
Answer: FalseCondensation is gas to liquid.5. Water drops on a cold bottle come from ______.
Show answer
Answer: condensationWater vapour turns to liquid.6. Give one example of melting from home.
Show answer
Answer: E.g. ice melting, shea butter melting.Solid to liquid.
Homework
- Put an ice cube on a plate. Time how long it takes to melt.