Hardness is one of the property that the Primary School pupils need to learn. Pupils usually use the word hard and strong interchangeably. However, this is not accepted in Primary School Science as hardness and strength re two very different concepts. For hardness, we are talking about how “scratchable”. As for strength, we use the “put-weight-until-it-break” test. Here are some of my ideas on hardness
Gorilla Glass
Check out this article on the screen on most mobile phones might be scratch-resistance and there might not be a need for screen protector . Thanks to Gorilla Glass. We can use that article as a starter to discuss about the property of materials
Chopping Board
In order to make the pupils remember this, I would use the chopping board example. Will get the kid to read the article at Fast Facts About Cutting Boards and Food Safety in Your Kitchen and get them if they can articulate the property being highlighted in the article.

ScreenGrab from Fast Facts About Cutting Boards and Food Safety in Your Kitchen