1. Summary of This Week’s Lab Conductometer Thermal Expansion Convection

2. Conductometer View the Video View the Video -Order from best to worst conductors:  Copper  Aluminum  Brass*  Stainless Steel*  Nickel * alloys

3. Thermal Expansion  Ball and Ring Lab - View the Video View the VideoView the Video  Thermal Expansion – when molecules are heated  Molecules move further apart and take up more space  Objects get bigger  Contraction – when molecules cool down  Molecules move closer together and take up less space  Objects become smaller  PBS activity PBS activity PBS activity

4. Everyday Examples  Bridges have “teeth” or expansion joints  Concrete sidewalks have spaces or grooves  Exception to the rule: between 32 and 39 water freezes and expands  Ice is less dense than water and floats

5. Convection  Heat transfer caused by density differences  Liquids and gases  Hot gases or liquids- rise because it’s less dense  Cold gases or liquids- sink because it’s more dense

6. Convection  Look at the following site and copy down the picture of the radiator- mark the heat flow with 2 different colored pens/pencils  http://www.stovesonline.co.uk/stove-heat- distribution.html http://www.stovesonline.co.uk/stove-heat- distribution.html http://www.stovesonline.co.uk/stove-heat- distribution.html  View the animation View the animation View the animation  View the animation View the animation View the animation

7. Radiation  Transfer of energy by electromagnetic waves  Doesn’t require a medium (solid, liquid or gas) or particles  How heat/infrared energy gets here from the sun  Example: outer space- vacuum  Lab- Radiometer pgs 53-55

8. Overall summary Heat is transferred in 3 ways: Conduction Convection Radiation It travels from hot to cold places. It is measured in calories. Temperature change = Final Temperature – Initial Temperature Heat = Volume X Temperature change

9. CONDUCTION Heat transfer by contact/collisions Happens in solids Better in high density objects

10. Convection Hot air/water is less dense and will rise. Cold air/water is more dense and will sink. This results in convection currents.

11. Radiation Doesn’t require a medium (solid, liquid or gas) Can happen through outer space or empty space (a vacuum) Energy travels as light wave and some of it is then converted back to heat