Solids, Liquids and Gases

Everything around you is made of matter, and most matter comes in three states: solid, liquid, and gas. Ice, water, and steam are all the same stuff — just water in three different states! Matter is anything that takes up space and has mass.

In a solid, the particles are locked together in a fixed pattern and can only vibrate on the spot. That is why a solid keeps its own shape and does not flow. Think of a brick, a coin, or an ice cube — they stay put unless something forces them to change.

In a liquid, the particles are still close together but they can slide past one another. This is why a liquid flows and takes the shape of whatever container you pour it into, yet keeps the same volume. Water, juice and oil are all liquids.

In a gas, the particles have lots of energy and spread out to fill all the space available. That is why a gas has no fixed shape or volume — it expands to fill its whole container. The air around you is a mixture of gases, even though you cannot see it.

Heating and cooling can change the state of matter. Heat ice and it melts into water; heat water and it boils into steam. Cool steam and it condenses back into water; cool water and it freezes back into ice. The particles do not change — only how much energy they have and how they move.

Here is something that surprises many people: when water freezes into ice, it actually takes up MORE space than the liquid water did. That is unusual — most things shrink when they cool. It is why ice floats on water and why a fizzy drink can burst if you leave it in the freezer too long.