Physics heat

1. Yes, both processes require a medium.
Any metalic substance (e.g. iron, copper) is a good conductor of heat. Any fluid (liquid or gas, e.g. water, air) is a medium for convection to take place.

2. Infrared radiation is commonly known heat-rays. It is a means of transferring heat by the radiation process.

In theory, any heated substance can emit electromagnetic waves at other wavelengths apart from infared. But infared contributes to the highest intensity among the emitted waves.

3. Evapoartion normally occurs on the surface of a liquid, and takes place at temperatures below the boiling point. Boiling occurs in the whole liquid (i.e. not limited to the surface) and is more vigorous.

As such, you could still say that evaporation occurs on the surface at boiling point. But at that time, boiling dominates.

4. Fire is in the "plasma state"(等離態), the 4th state of matter.

5. Heat is transferred by direct contact.

6. A fluid is a substance that has no definite shape. It normally takes the shape of its container.

All liquids and gases are fluid.

想當年,這topic非淺。