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Solid, liquid or gas?

Water in its solid and liquid statesWater in its solid and liquid statesMost substances exist in one of three states: solid, liquid or gas. They change from one state to another when they are heated or cooled. Water is a liquid at room temperature, but if you freeze it, it becomes a solid (ice). When boiled it turns into a gas (water vapour or steam).


Matter in its solid, liquid and gassy statesMatter in its solid, liquid and gassy states

Water as a solid (ice), liquid and gas (water vapour)Water as a solid (ice), liquid and gas (water vapour)


The molecules in a solid are tightly packed and do not move about much. This is why solids have a fixed shape. The molecules in a liquid are not all joined together. They move about more and spread out to fill the shape of their container. The molecules in a gas are far apart. They move about a lot and fill the container they are in. This is why gases have no fixed shape. 

Solids can change directly into gases. This process is called sublimation.

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