Physics - Fizik

Most subtances enlarge or expand as they heat up, and becomes smaller or contract as they get colder. But water is unusual. It contracts as it cools down to 4 0C. Then, as it gets even colder and freezes into ice, it expands again. This means a lump of ice at 00C weighs less than the same sized lump of water at 100C. So ice from an ice cube in a drink to a giant iceberg in the ocean- floats on water.

The energy we receive from the Sun is called solar energy. It consists mainly of light and heat that travel through space. These forms of energy come from atoms smashing into each other in the centre of the Sun and joining together, or fusing. This process is called nuclear fusion as we study in form 5. Energy thar comes from the centres or nuclei of atoms is called nuclear energy. The form of nuclear energy in nuclear power stations here on Earth comes from nuclear fission, when atoms split apart.