Changing States

a substance may not always in the same state of matter.it can change state when it is at different temperatures.For example , a solid can become a liquid if it become hot enough and a liquid may become a solid if it is cooled enough.

Boiling and evaporation

when water is heated to boiling point ,bubbles appear.These bubbles are made become some of the liquid has changed to an invisible gas called water vapor ,or steam.Water boils at 100C (212F).The water vapor escapes into the air in a process called evaporation.Evaporation can also occur more slowly. For example,wet hair dries because of evaporation.

Condensation

The opposite of evaporation and this process occurs when a gas cools and become a liquid.When water vapor comes into contact with something cool,it tuns back into a liquid.Condensation often on windows as the temperature drops overnight.

Freezing

When a liquid become cold enough it will freeze and become a solid.The temperature at which a substance turns into a solid is called its freezing point.Water freezing at 0 C (32 F) and its solid state is called ice .Jet fuel freezing at around -47C(-52F).

Melting

When a solid is heated to a high enough temperature ,it becomes a liquid ,or melt .The increase in temperature causes the particles in the solid to move more freely unit eventually they achieve a liquid state. The temperature at which a solid becomes a liquid is known as its melting point.The melting point and freezing point of a substance are the same temperature.