Changes in states of matter

Matter can change from one state to another. This can happen in many ways including freezing, melting, evaporation, condensation and sublimation.

Freezing

If water is placed in a freezer it will turn into ice. This is called freezing. It happens because heat is removed from the water causing it to change from liquid to solid. The temperature at which water freezes is 0^o Celsius.

^{Ice is simply frozen water}

Melting 

Some solids melt if you add enough heat to them. For example, if you take ice from the freezer and put it on the kitchen counter, it will soon start to turn into liquid water. This is called melting. The meting point of water is 0^o Celsius. Metals like iron also melt is they are heated to very high temperatures.

^{At very high temperatures, iron melts and becomes hot, glowing, liquid iron.}

Evaporation 

When enough heat is added to a liquid, it may turn into a gas. This known as evaporation. For instance, after water starts to boil, it begins to change into a gas called water vapour.The boiling point of water is 100^o Celsius. Another example is when rubbing alcohol evaporates after you rub it on your skin. 

^{In the photo, liquid water is turning into water vapor.} 

Condensation

Sometimes gases can change into liquids when they are cooled. This is called condensation. For example, when water vapour is cooled it turns into liquid water. Clouds are formed when water vapour condenses high in the atmosphere. If you pour a cold drink into a glass, tiny drops of water will condense on the outside of the glass. This is because the cold glass cools the air near it and causes the water vapour in it to turn into liquid water.

^{Water vapour condenses high in the atmosphere and forms clouds.}

^{Water vapour condenses on the outside of a cold glass.}

Sublimation 

Sometimes matter changes from a solid directly into a gas. It does not turn into a liquid first. Dry ice (frozen carbon dioxide) changes directly into carbon dioxide gas. This is sublimation. In very cold places, snow sometimes turns directly into water vapour without melting first. This is also sublimation. In the video below, dry ice is placed in water. You can see it turning directly into a gas.