THIRD PERIOD

Third PERIOD

·      CHANGES IN MATERIALS: reversible and irreversible changes, changes by heating and cooling ( melting, freezing) and Dissolving.

·      Light and dark

·      Electricity   

Changes in Materials

CHANGING MATERIALS 

materials  can be changed by heating or cooling
Heating or cooling can cause materials to change state. Water is a great example to use in all three states with evaporation, condensation, melting and freezing.

What does it mean when materials change state?

Materials can be changed from one of the three states to another by certain processes, usually heating or cooling. An example would be liquid water which can be changed into steam by heating or cooled to form solid ice.

watch the video

• If water is cooled enough, it can change to ice.

look at the video about water freezing https://players.brightcove.net/2698740430001/default_default/index.html?videoId=6017863651001



 • If ice is warmed enough, it can change to liquid water.
look at the video about ice melting
https://players.brightcove.net/2698740430001/default_default/index.html?videoId=6017800192001

 Water can be cooled to make ice and then the ice can be warmed to make liquid water again.
Cooling and heating water in this way can make the changes go back and forth

• Heating a substance makes the molecules move faster. • 

Cooling a substance makes the molecules move slower.

MATTER CHANGES WHEN IS HEATED OR COOLED

FROM SOLIDS TO LIQUIDS

MELTING

molecules gain energy and start moving faster, sliding over each other.

FROM LIQUIDS TO GAS

EVAPORATION

molecules gain energy and start moving faster, molecules spread through out the space.

FROM GAS TO LIQUID 

CONDENSATION

Molecules lose energy, packed close together sliding over each other.

FROM LIQUID TO GAS

FREEZING 

Molecules lose energy, packed very close to each other not moving around but vibrating.

melting

evaporation

freezing 

materials can  be changed by force

1. squash

2.  stretch 

3. bend 

4.twist

MATERIALS CAN CHANGE WITH WATER

DISSOLVE OR NOT DISSOLVE