Thermal Energy

Question 1

describe conduction

Answer 1

• transfer of thermal energy in solids and liquids through the vibration or contact of particles

-as a substance is heated up, the molecules vibrate more hitting each other and causing adjacent molecules to vibrate more, transferring thermal energy (heat) from hot parts to cooler parts

Question 2

describe convection

Answer 2

• transfer of thermal energy in liquids and gases

-convection occurs as molecules in a fluid move from an area of high to low thermal energy by a convection current

-when fluid is heated up, it expands and becomes less dense so rises and displaces the colder fluid

Question 3

describe radiation + example

Answer 3

• transfer of thermal energy which does not require a medium

-infrared radiation

Question 4

everyday examples of the role of convection

Answer 4

-boiling water in a pot
-radiator

Question 5

explain how emission and absorption of radiation are related to surface and temperature

Answer 5

-the higher the temperature and the greater the surface area the more infrared radiation emitted

-black/matt is the best absorber and emitter of radiation
-white/shiny are the best reflectors of radiation

Question 6

explain ways of reducing unwanted energy transfer

Answer 6

-through insulators which are poor conductors (e.g. non-metals: foam, feathers, glass fibre)

-they prevent heat transfer by conduction and the trapper air prevents convection currents

-double-glazed windows/carpets in houses help retain heat

Question 7

what is conduction, convection and radiation

Answer 7

all are types of thermal energy transfer

Question 8

examples of conduction

Answer 8

-barbecue

Question 9

explain how a radiator works

Answer 9

• air is heated by the radiator
  -hot air expands and is less dense so it rises
  -the cool air at the top, goes down because it is more dense
  -forms a convection current
  -this process repeats until air circulates all the thermal energy around the room

Question 10

examples of good conductors

Answer 10

metals

Question 11

examples of bad conductors

Answer 11

non-metals