What is hardness?

Hardness is how strong something is when you try to scratch it or press on it.

Imagine you're playing with your favorite building blocks, some are easy to push around, like soft clay, while others feel stiff and tough, like a brick. Hardness is like that, it tells us how much force we need to make a mark on something or change its shape.

Think of a rock in the playground, if you try to scratch it with your fingernail, nothing happens. But if you use a piece of glass, it might leave a tiny line. That’s because glass is harder than your nail. People sometimes use a tool called the Mohs scale, which ranks materials from 1 (the softest) to 10 (the hardest), like how we rank our favorite toys.

If you're drawing with crayons on paper, it's easy, but if you try to draw on a rock, it’s much harder! That’s why hardness helps us know what tools we need to use for different jobs.