unit 9- thermal properties of matter

solid to liquid: melting

liquid to gas: boiling or evaporation

gas to liquid: condensation

liquid to solid: freezing or solidification

Melting

when a solid changes to a liquid upon heating is called melting.

At 0 degrees, the molecules in a solid gain enough energy to overcome the force of attraction and becomes less orderly. Now, the molecules can move out of their fixed positions. melting has already taken place.

Solification/ freezing point

- when a liquid changes to a solid is called freezing or the reverse process of melting called solidification.

As temperature decreases. molecules in a liquid lose energy and move closely together. now the molecules cannot move but only vibrate in its fixed positions. freezing has taken place.

Boiling and evaporation

- when a liquid changes into a gas

First, the molecules gain energy and move faster. At 100 degrees, the molecules gain enough energy to overcome the force of attraction increases. they will move further away, boiling has then taken place.

evaporation is also the change of state of liquid to gas. however, they have their differences.

1) boiling takes place only at a certain temp. but evaporation takes place at any time.

2)boiling takes place faster than evaporation

3)boiling takes place thoughout the liquid whereas evaporation takes place only at the surface

4)the temp. wil remain constant for boiling however may vary for evaporation.

5)bubbles are formed during boling but not during evaporation

6)energy souce is needed for boiling whereas evaporation does not.

factors affecting the rate of evaporation

-temperature:high temp will increase the rate of evaporation

- humidity:high humidity causes the rate of evaporation to decrease

- surface area of liquid: the larger the surface area of a liquid, the higher the rate of evaporation

-pressure:to increase the rate of evaporation, a low pressure is needed.

YEAH! ALL COVERED!