Question

which substance increases its volume when it becomes a solid? salt water mercury

Explanation:

Water is a unique substance. When it freezes and becomes a solid (ice), its volume increases. This is because the water molecules arrange themselves in a hexagonal lattice structure when freezing. In this structure, there is more empty space between the molecules compared to the liquid state. For most substances, the solid state is denser (has less volume for the same mass) than the liquid state. But for water, the opposite is true. Salt is already a solid in its normal state (at room - temperature, it's a crystalline solid), and mercury is a liquid metal at room temperature. When mercury freezes (becomes a solid), its volume decreases like most substances.

Answer:

Water