1. Thermal Energy 11/1/2011

2. What is thermal energy? Thermal energy is also known as heat and is the kinetic energy of all the molecules in a material. If molecules are moving fast… – (1) Do they have more or less kinetic energy? – (2) Does the material have more or less thermal energy? – (3) Do you predict it will be a high or low temperature?

3. Temperature Temperature is a number related to the average kinetic energy of the molecules of a substance. Heat, however, IS the energy in a substance and is measured in Joules, just like all the kinds of energy we have been talking about. http://phet.colorado.edu/en/simulation/gas-properties What happens to the molecules in a gas when you add more energy or heat to the gas? Describe what you see in the simulation.

4. Heat Heat is thermal energy that is transferred between two bodies due to a difference in temperature. If one object is higher temperature than the other, heat will flow from high to low temperature. Heat transfer is the process of increasing the kinetic energy of a materials’ particles from a material of high temperature to one of lower temperature.

5. Three kinds of thermal energy transfer Conduction Convection Radiation

6. Conduction Conduction is the transfer of heat by direct contact (mostly with solid objects). Molecules in one material can increase the energy of molecules in the other material. Materials that allow heat to flow through them are called conductors (metals are good conductors). Materials that do not conduct heat well, such as plastic and wood, are called insulators.

7. Convection Convection is the transfer of heat by the movement of the medium itself and occurs in liquids and gases but not in solids. Hot areas of the material flow and mix with cool areas (like in air conditioning). Convection transfers heat over a distance faster than conduction but cannot transfer to solid objects.

8. Radiation Radiation is the transfer of heat in the form of waves through space. Hot objects give off infrared electromagnetic radiation, which can be absorbed in another object and heat it up. Transfer of heat by radiation moves at the speed of light and can go great distances, for example from the Sun to the Earth.

9. Exit Slip (turn in!) What is thermal energy? If you add heat to air in a balloon by putting it over a candle, what kind of heat transfer are you using? For that balloon, what do you think would happen to the air molecules inside?