Affects of Heating and Cooling Lesson 18

In our last lessons we learned that heat will always flow in one direction from hot to cold.

We also learned heat can be transferred from one place to another by three methods: Conduction, Convection and Radiation.

Conduction occurs when two object at different temperatures are in contact with each other. Heat flows from the warmer to the cooler object until they are both at the same temperature.

Convection is the movement of thermal energy by the movement of liquids or gases.

Radiation is a method of heat transfer that does not rely upon any contact between the heat source and the heated object.

When you are transferring heat you can change the properties of the materials you are using.

Heat affects different substances in different ways. When you heat a solid, it melts. In the example where the man put the hot fork on the ice, the ice quickly started to melt.

The solid became a liquid.

If we put the melted ice in the freezer it will eventually refreeze and become solid again.

When we heat a liquid it will turn into a gas. We see this when we boil water. We see steam appear. Steam is water which has turned from a liquid to a gas.

You may notice as you work with heat transfer many kinds of changes occur faster at higher temperatures.

That is because all matter is made up of atoms.

As matter heats, the atoms become more active (since heat is energy), thus making the atoms move more freely.

This looses bonds, and can make a solid object into a fluid (liquid or gas).

Nearly all substances increase in volume when they get hotter. Metal will expand when it gets hot.

=QYIgYc-HHV0 Let’s watch this video about heat and properties of matter.

Some materials are better conductors of heat than other materials.

Conductors : A good conductor of heat is a material that transfers heat energy from a region of higher temperature to a region of lower temperature faster.

Metal will heat quickly and the transfer of heat will go throughout the entire metal cooking pot. This makes metal a great tool to use when cooking food.

Metals are good conductors of heat such as copper, gold and aluminum. Wood is not a good conductor of heat.

Thermal energy can be conducted through the metal handle of this metal pot. By touching the metal handle you can burn your hand.

=OWhZ-WBfATc Let’s watch this video about good and bad conductors of heat.

Let’s review. Answer the attached questions on the worksheet entitled L#18 Affects of Heating and Cooling.

In our next lesson we will review what we have learned about Energy from this unit.

Good Job Today! And remember to….

See you next time!