Key Stage 4
Meaning
Melting point is the temperature at which a solid can become a liquid.
About Melting Points
- Different substances have different melting points.
- The melting point of a substance is determined by the strength of the bonds which hold the particles in fixed positions in a solid. The stronger the bonds the higher the melting point.
- When a substance is heated to its melting point it will remain at this constant temperature until all of the solid has melted.
- The melting point of pure water ice is 0°C or 273 Kelvin.
- Adding salt to ice can lower its melting point, causing it to melt at a lower temperature.
- Transition Metals generally have very high melting points, except for Mercury which is liquid at room temperature.
Detecting Purity
- The purity of a sample can be determined by observing its melting point. If the melting point is spread over a range of temperatures or different from the known values for the pure substance then the sample is not pure. For example to test if a sample of Water is pure it can be melted from Ice which should happen at exactly 0°C if it does not then it is not pure.