Hard or soft?

Press different objects with your hands. Some, like a stone, are hard to compress (squeeze). Others, like an eraser, squeeze easily.

Now try to scratch materials with a metal key: wood, aluminium, stone, iron, a candle, chalk. Some scratch much more easily than others.

Materials that can be compressed or scratched easily are soft. Materials that are difficult to compress or scratch are hard. So a stone is hard; an eraser, a sponge and candle wax are soft. A brick, made of baked clay, is hard.

But hard and soft are relative: it depends on what you compare. Rubber is harder than sponge, but softer than iron. The same material can be 'harder' next to one thing and 'softer' next to another.