what makes metal hard?
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Not all metal *is* hard. Lithium is a metal but you can easily cut it with a knife. At the other end of the scale you get tungsten, which is the hardest metal you’ll find in nature, although still nowhere near as hard as diamond. As for what causes those differences, it largely comes down to the crystal structure the metal atoms tend to fall into.
Molecular cohesion. There’s probably an actual scientific name for it but in short it’s how tightly each atom and molecule of a substance holds onto it’s neighbors. In some metals like gold and copper this force is very loose while in metals like iron and tungsten this force is far tighter. You can also increase the hardness of a metal by putting stress on it. Imagine pulling a string taut and this is essentially what happens when quenching steel.
Not all metal is hard, lead can me shaped by hand and mercury is even a liquid at room temperature. Substances that are hard, are this way because there molecules are very close together. The softer something is, the more space between molecules.
Edit: and molecules start bouncing around when heated, that’s why a substance usually gets softer when heated like when forging metal.
It is the combination of speed, technical difficulty, and intensity at which its played that makes metal hard. Also, the image of long haired musicians head banging in lockstep with their music makes it extra hard.
The chugging guitars, the heavy bass and the rapid double kick drums. Throw in a little screaming for some extra “hard”.
As others have pointed out there are soft metals.
Iron can be relatively soft if it’s very pure. It deforms very easily when compared to a ceramic, which is really hard and will shatter instead of bend.
The reason for this is that the atoms in iron are able to slide past each other (more or less). And this is because they’re all the same type of atom in a sea of electrons.
Impurities can be purposefully be added to make iron harder. These impurity atoms get in the way of the “sliding”. Steel is harder, but in turn it is more brittle.
The secret of steel has always carried with it a mystery. You must learn its riddle, You must learn its discipline. For no one – no one in this world can you trust.
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