Summary of This Week’s Lab Conductometer Thermal Expansion Convection
Conductometer View the Video View the Video -Order from best to worst conductors: Copper Aluminum Brass* Stainless Steel* Nickel * alloys
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
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
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
Convection Look at the following site and copy down the picture of the radiator- mark the heat flow with 2 different colored pens/pencils distribution.html distribution.html distribution.html View the animation View the animation View the animation View the animation View the animation View the animation
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
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
CONDUCTION Heat transfer by contact/collisions Happens in solids Better in high density objects
Convection Hot air/water is less dense and will rise. Cold air/water is more dense and will sink. This results in convection currents.
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