Matter, energy and change
Basic Science · BECE · JSS (BECE)
Solid, liquid, gas — and what you do to move between them — is a whole BECE favourite.
What you need to know
- Solid: fixed shape and volume, particles packed and vibrating. Liquid: fixed volume, takes the container’s shape. Gas: no fixed shape or volume.
- Melting and boiling need heat in. Condensing and freezing give heat out.
- A mixture can be separated (salt and sand, ink by chromatography). A compound cannot, except by a chemical reaction.
- Elements: metals (left and middle of the periodic table) and non-metals. Symbols: Na sodium, K potassium, Fe iron, Cu copper, Cl chlorine.
- Physical change is reversible and no new substance (ice → water). Chemical change makes a new substance (burning paper).
- Energy types: kinetic, potential, heat, light, sound, electrical, chemical. Energy is transformed, not destroyed.
The mistake to avoid
Dissolving sugar is a physical change — you can get the sugar back by evaporating the water. It is not “gone”.