Summary of This Summary of This Week’s LabWeek’s LabConductometer Conductometer

Thermal ExpansionThermal Expansion

ConvectionConvection

ConductometerConductometer

View the VideoView the Video

-Order from best to worst conductors:-Order from best to worst conductors: CopperCopper AluminumAluminum Brass*Brass* Stainless Steel*Stainless Steel* NickelNickel

* alloys* alloys

Thermal ExpansionThermal Expansion

Ball and Ring Lab - Ball and Ring Lab - View the VideoView the Video Thermal Expansion – when molecules are Thermal Expansion – when molecules are

heatedheated Molecules Molecules move further apartmove further apart and take up more and take up more

spacespace Objects get biggerObjects get bigger

Contraction – when molecules cool downContraction – when molecules cool down Molecules Molecules move closer togethermove closer together and take up less and take up less

spacespace Objects become smallerObjects become smaller

PBS activityPBS activity

Everyday ExamplesEveryday Examples

Bridges have “teeth” or expansion jointsBridges have “teeth” or expansion joints Concrete sidewalks have spaces or Concrete sidewalks have spaces or

groovesgrooves

Exception to the rule: between 32 and Exception to the rule: between 32 and 39 water freezes and expands39 water freezes and expands Ice is less dense than water and floatsIce is less dense than water and floats

ConvectionConvection Heat transfer caused by density Heat transfer caused by density

differencesdifferences Liquids and gasesLiquids and gases

Hot gases or liquids- Hot gases or liquids- riserise because it’s because it’s less less densedense

Cold gases or liquids- Cold gases or liquids- sinksink because it’s because it’s more more densedense

ConvectionConvection

Look at the following site and copy down the Look at the following site and copy down the picture of the radiator- mark the heat flow with picture of the radiator- mark the heat flow with 2 different colored pens/pencils2 different colored pens/pencils

http://www.stovesonline.co.uk/stove-heat-http://www.stovesonline.co.uk/stove-heat-distribution.htmldistribution.html

View the animationView the animation

View the animationView the animation

RadiationRadiation

Transfer of energy by electromagnetic wavesTransfer of energy by electromagnetic waves Doesn’t require a medium (solid, liquid or gas) or Doesn’t require a medium (solid, liquid or gas) or

particlesparticles How heat/infrared energy gets here from the sunHow heat/infrared energy gets here from the sun

Example: outer space- Example: outer space- vacuumvacuum

Lab- Radiometer Lab- Radiometer pgs 53-55pgs 53-55

Overall summaryOverall summaryHeat 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 CONDUCTION

•Heat transfer by contact/collisions

•Happens in solids

•Better in high density objects

ConvectionConvection•Hot air/water is less dense

and will rise.

•Cold air/water is more dense

and will sink.

•This results in convection currents.

RadiationRadiation

•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