What are materials?
Materials are the substances objects are made from.
Examples: Wood, Metal, Plastic, Glass, Fabric, Rubber, Stone
Different materials have different properties.
Properties of Materials
Properties are the characteristics that describe a material.
Some common properties are:
- Hard – difficult to scratch or bend (e.g. metal, stone)
- Soft – easy to squash or bend (e.g. cotton, sponge)
- Flexible – can bend without breaking (e.g. rubber)
- Rigid – cannot bend easily (e.g. wood)
- Transparent – you can see through it clearly (e.g. glass)
- Translucent – lets some light through (e.g. frosted glass)
- Opaque – blocks light (e.g. wood)
- Waterproof – does not let water pass through (e.g. plastic)
- Absorbent – soaks up liquids (e.g. paper towel)
Why do we choose certain materials?
We choose materials because their properties make them suitable for a particular purpose.
Solids, Liquids and Gases
Properties of Solids
- Keep their own shape.
- Have a fixed volume.
- Particles are tightly packed.
Examples: book, table, rock
Properties of Liquids
- Flow and take the shape of their container.
- Have a fixed volume.
Examples: water, juice, oil
Properties of Gases
- Spread out to fill any space.
- Have no fixed shape or volume.
Examples: air, oxygen, steam
Changes of State
A change of state happens when a material changes between solid, liquid and gas.
Melting
Solid → Liquid
Example: Ice → Water
Freezing
Liquid → Solid
Example: Water → Ice
Evaporation
Liquid → Gas
Example: Water → Water vapour
Condensation
Gas → Liquid
Example: Water vapour → Water droplets
Dissolving
Some substances dissolve in liquids.
The substance that dissolves is called the solute.
The liquid it dissolves in is called the solvent.
Together, they form a solution.
Examples:
- Sugar + water form sugar solution
- Salt + water form salt solution
Examples of substances that do not dissolve: Sand, Stones and Oil etc.
Reversible and Irreversible Changes
Reversible changes
A reversible change can be undone.
Examples: Melting ice, Freezing water, Dissolving salt in water (the salt can be recovered)
Irreversible changes
An irreversible change cannot be undone.
Examples: Burning paper, Cooking an egg, Baking a cake, Rusting metal
Separating Mixtures
Different methods can be used.
Filtering
Separates an insoluble solid from a liquid.
Example: Sand and water
Sieving
Separates materials of different sizes.
Example: Flour and lumps
Evaporation
Separates a dissolved solid from a liquid.
Example: Salt from seawater
Magnetism
Separates magnetic materials.
Example: Iron filings from sand
Key Vocabulary
Material, Property, Transparent, Translucent, Opaque, Waterproof, Absorbent, Flexible, Rigid, Soluble, Insoluble, Solution, Dissolve, Reversible change, Irreversible change, Evaporation, Condensation and Filtering
