In Natural Sciences & Technology, Grade 4 learners investigate how materials and matter can change from one form to another. For example,from Solid to a liquid to a gas. The materials around us are at room temperature. When we describe a material as being a solid, liquid or gas, we are usually describing them at room temperature. We can change a material into its other states by heating it up or cooling it down.
For example, water is a liquid at room temperature.
If we cool it down, it changes into a solid – ice.
If we heat it up, it changes into a gas – steam.
A particular material changes from being a solid to a liquid at a fixed temperature. This is its melting point.
Ice melts to form water at 0 °C. So its melting point is 0 °C.
We can easily reverse this process. If we cool water below 0 °C, it freezes to form ice. So we also call this temperature the freezing point of water.
The melting point and freezing point for any material are the same.
Learners are being assisted by a student Teacher from Wits (Ms Nompumelelo Malinga)