What makes salt a hard substance?

Salt is a hard substance because of its crystalline structure. The atoms in salt are arranged in a regular, repeating pattern, which gives it a rigid and solid structure. This arrangement of atoms makes it difficult to break or deform the salt crystals, resulting in its hardness. Additionally, the strong electrostatic forces between the positively charged sodium ions and negatively charged chloride ions in salt also contribute to its hardness.

Salt (sodium chloride) is not a hard substance. It is a crystalline solid that is relatively soft and can be easily crumbled or crushed.