The sun emits heat that has lessened in intensity when it reaches Earth after traveling through a great distance. A spoon placed in a cup of hot milk becomes hot up to its handle. The water in a kettle boils after several minutes of being placed on a heated stove. How do all these happen? How is heat transferred in each of these examples?

When there is a difference in temperature in one area, heat naturally moves from the higher to the lower temperature. This movement causes the transfer of heat, which can take place in either of three natural processes: conduction, convection, and radiation.

Conduction

When two objects come into close contact with each other, the heat in the hotter object will flow to the cooler object so they will achieve equilibrium, or the state where both objects have the same temperature. Heat causes molecules to move faster and collide with the molecules near it, transferring the heat from molecule to molecule. You may not be aware of it but this is what happens when you put ice cubes into a glass of tap water. The molecules in the ice cubes will move faster while those in the tap water will slow down until the water and the ice cubes are of the same temperature. This form of heat energy transfer is called conduction.

Have you wondered why the handles of most steel or copper frying pans are covered with or made of plastic? Metals like aluminum, iron, steel, and copper are examples of conductors of heat. You are likely to burn your fingers if you touch any of these metals while they are hot. This explains why the handles of most frying pans are covered in plastic. Plastic is an insulator, or a material that does not transmit, conduct, or allow heat to pass through.

Many cooking utensils have parts that are made with insulators such as rubber, wood, and plastic for safety purposes.