UD 7. PREVIOUS KNOWLEDGE

MATTER, ENERGY AND FORCE

Matter has got mass and volume:

·         Mass is how much matter an object has got. We measure mass in kilogrammes and grams using scales. If an object weighs a lot, it has got more mass.

·         Volume is how much space an object occupies. We can measure volume using a measuring jug.

The states of water:

Water is matter. Matter can change when it is heated or cooled. Water can change its state. Water can be in a solid state, like ice. It can be a liquid state, like in rivers. It can also be in a gaseous state, like water vapour.

·         If we heat solid water (ice), it becomes water vapour.

·         If we heat liquid water, it becomes water vapour.

·         If we cool water vapour, it becomes liquid water. 

Force.

There are two types of force: contact force and distance force. Contact force is produced when we touch objects to move them or change their shape. When we hit a balloon, we produce force and the balloon moves. When we squeeze a sponge we produce force and the sponge changes shape. Distance force is produce without touching an object. Gravity is a distance force. It causes objects to fall to the floor. Magnets are materials that create distance force. If you put a magnet near a small, metal object, the object jumps onto the magnet. Compasses use magnets, these are instruments that tell us the cardinal points.