Materials: Hardness
One way to group materials is by their hardness.
There is good reason for grouping materials this way. If you came across an unknown material, one way you could find out what it is is by seeing how hard it is.
There is a scale for hardness called Moh's
Hardness Scale. This scale starts at 1 for the softest material to 10 for the hardest.
You don't have to know them all but it is interesting to find out about the hardest and softest materials we know.
| Material | Hardness scale |
| Talc | 1 |
| Gypsum | 2 |
| Calcite | 3 |
| Flurorite | 4 |
| Apartite | 5 |
| Feldspar | 6 |
| Quartz | 7 |
| Topaz | 8 |
| Corundum | 9 |
| Diamond | 10 |
Here you see that Talc is the softest of the materials (good job really)
- can you imagine putting talc on to dry your skin after a bath if it was no so
soft? Ouch!
Diamond is the hardest material. Now you know why they put diamond on the tips of drills.
Did you know that your fingernail has got a hardness of about 2.5?
Now you know that, what two materials could you scratch with your nail?
Answer
Talc and Gypsum.
Glass has got a hardness of about 5.5. This is really interesting, because some so-called diamonds are made of glass.
What could you do to test to see if a diamond was real or not?
Answer
Did you get it?
If you scratch your diamond with quartz or topaz and it leaves a mark then it is not diamond it is a
fake!
Well that is about it for the hardness scale.
Before we go you could do an experiment.
GET PERMISSION BEFORE YOU DO THIS AND TAKE CARE!
Do you think that you can scratch a piece of glass with some steel?
Which do you think is the hardest material?
TRY IT!
Good luck!