What is matter?
Matter is anything that has mass and takes up space (volume). Your desk, water, air and even you are matter. Light, sound and heat are not matter, because they don’t have mass.
Measuring matter
| Property | What it means | Tool | Unit |
|---|---|---|---|
| Mass | How much matter | Balance or scale | grams (g), kilograms (kg) |
| Volume | How much space | Ruler, graduated cylinder | cm³, mL, L |
| Temperature | How hot or cold | Thermometer | °C |
To find the volume of an odd-shaped object like a rock, use water displacement: put water in a graduated cylinder, drop in the rock, and see how much the water level rises.
Physical properties
A physical property can be observed without changing what the substance is.
| Property | Example |
|---|---|
| Colour | Copper is reddish-brown. |
| Texture | Sandpaper is rough. |
| Hardness | A diamond is very hard. |
| Magnetism | Iron is magnetic. |
| Conductivity | Metals carry electricity and heat. |
| Solubility | Sugar dissolves in water; sand does not. |
| Density | A rock sinks; a cork floats. |
| Melting or boiling point | Ice melts at 0 °C. |
The three states of matter
The states of matter are solid, liquid and gas. Particles (tiny bits of matter) behave differently in each.
| State | Shape | Volume | Particles |
|---|---|---|---|
| Solid | Fixed | Fixed | Packed tightly; vibrate in place |
| Liquid | Takes the container’s shape | Fixed | Close together; slide past each other |
| Gas | Fills the container | Changes to fill the space | Far apart; move quickly in all directions |
Changes of state
| Change | From → To | Heat added or removed? |
|---|---|---|
| Melting | Solid → liquid | Added |
| Freezing | Liquid → solid | Removed |
| Evaporation / boiling | Liquid → gas | Added |
| Condensation | Gas → liquid | Removed |
| Sublimation | Solid → gas | Added (dry ice) |
Physical changes
A physical change changes the size, shape or state of matter, but no new substance is made.
- Cutting paper
- Melting ice
- Crushing a can
- Dissolving sugar in water
- Breaking glass
Many physical changes can be reversed. You can freeze water again or evaporate water to get the sugar back.
Chemical changes
A chemical change makes a new substance with new properties. It usually can’t be easily reversed.
Signs of a chemical change:
- a new colour appears (a banana turns brown; iron rusts)
- gas bubbles form (baking soda and vinegar fizz)
- light or heat is given off (a candle burns)
- a new smell appears (food spoils)
- a solid forms in a liquid
Examples: burning wood, baking a cake, rusting, cooking an egg, digesting food.
Mass is conserved
In both physical and chemical changes, matter isn’t created or destroyed. If you melt 100 g of ice, you get 100 g of water. When wood burns, its mass seems to vanish, but it has turned into gases and ash. If you could catch every bit, the total mass would stay the same.
Common mistakes
- Thinking dissolving is a chemical change. It’s physical; the sugar is still sugar.
- Thinking bubbles always mean a chemical change. Boiling water bubbles too, and that’s physical.
- Thinking air has no mass. A full balloon weighs slightly more than an empty one.
Try it yourself
Decide whether each is a physical or chemical change:
- Tearing a piece of paper
- Burning a piece of paper
- A puddle drying up
- Milk going sour
- A nail rusting
- Chopping carrots
(Answers: physical; chemical; physical; chemical; chemical; physical)
Quick recap
- Matter has mass and takes up space.
- Physical properties can be observed without making a new substance.
- Matter can be a solid, liquid or gas.
- Physical changes don’t make new substances; chemical changes do.
- Mass is conserved in all changes.