Heat and Temperature

Question 1

Thermal Energy

Answer 1

Can be transferred by conduction, convection, radiation or evaporation

Question 2

Temperature (°C) difference

Answer 2

causes thermal energy to flow from hot to cold.

Question 3

Conduction

Answer 3

Transfer of KE through a substance from molecules to neighbouring molecules through collisions.
Metals-collisions passing energy between free electrons-good conductor. Non-metals poor
Solids best-spacing and bonds between molecules
Trapped air-v. poor conductor, good insulator. Eg. saucepans

Question 4

Convection

Answer 4

Transfer of KE (TE) through a fluid by movement of whole regions of fluid.
A region of fluid is heated => molecules move faster so it expands => its density decreases => it rises taking KE with it and less dense fluid replaces it-convection current. Eg: freezer

Question 5

Radiation

Answer 5

Transfer of TE using electromagnetic waves (infra red)
Can travel through vacuum-no particles needed
Dull, dark surfaces = good emitters and absorbers of heat radiation. Shiny, light surfaces opposite. Eg. toaster

Question 6

Evaporation

Answer 6

High KE atoms near the surface of a liquid escape, lowering the average KE of the liquid as a whole => lowering its temp.

Question 7

Convection demonstration

Answer 7

Book

Question 8

Radiation Exp.

Answer 8

Book

Question 9

Preventing heat loss (home insulation)

Answer 9

Cavity wall insulation-traps air
Loft insulation-traps air
Shiny foil behind radiator-prevents radiation

Question 10

Vacuum Flask

Answer 10

Reduces the transfer of heat by conduction, convection or radiation.
Conduction-plastic case + vacuum-traps air
Convection-Stopper + vacuum
Radiation-Silvering