Skip to content
MeerkatSkool Afrikaans
Summaries · Grade 7 Natural Sciences › Energy and heat transfer
Free summary · Grade 7 Natural Sciences

Energy and heat transfer

Conduction, convection and radiation, insulators, and the law of conservation of energy. Read one part at a time and tap “I know this”. Then test yourself in the quiz.

Know it already? Jump straight to the quiz

Your progress0 of 4

Three ways

Conductionthrough a solidConvectionwarm liquid or gas risesRadiationwaves, even through space
Heat moves in three ways.
  • A metal chair feels colder than a wooden one at the same temperature: metal conducts heat away from you faster.
  • A convection current spreads warmth through the air in a room.
  • The Sun’s heat reaches us by radiation.
  • Evaporation is not one of the methods of heat transfer.
Conduction, convection and radiation.
Conduction, convection and radiation.
Tap when you could tell someone without looking.

Insulate and reflect

  • A winter jersey keeps you warm: air is trapped between the fibres.
  • A house’s ceiling is insulated: most heat escapes through the roof.
  • A dark surface absorbs more radiation; in the desert people wear loose white clothing.
  • A vacuum flask: the vacuum (airless gap) stops conduction and convection, the shiny walls reflect radiation back, and the stopper stops heat escaping by convection at the top.
Tap when you could tell someone without looking.

Energy is conserved

In a closed system the total energy stays constant. A runner changes chemical energy into movement; a solar panel changes light into electricity. When a car brakes, movement energy becomes heat. A filament bulb is inefficient: most energy becomes heat.

Tap when you could tell someone without looking.

Insulation at home

  • A hot box (wonder box) is a box full of insulation: put a boiling pot inside, and the food keeps cooking without power.
  • A cool box keeps cold things cold, because the insulation stops heat from coming in from outside.
  • Insulation in the ceiling keeps the house warm in winter and cool in summer. Jerseys, beanies and blankets are insulation for the body.
  • Many traditional homes in South Africa, with thick clay walls and thatched roofs, are built to stay cool in the heat and warm in the cold.
Tap when you could tell someone without looking.

Remember this and test yourself

Remember this: your summary
  • Conduction: heat by direct contact in a solid. Convection: by a moving liquid or gas. Radiation: by waves, even through empty space.
  • Heat always flows from hot to cold.
  • Warm air rises, because it is less dense; that is why a kettle’s element is at the bottom.
  • An insulator conducts heat poorly; air pockets (wool, foam plastic) insulate best.
  • Energy cannot be created or destroyed: conservation of energy. Unit: the joule.

Write these points in your book. Read them again the night before the test.

Memory trick

Conduction = by touching (solids). Convection = by currents (liquids and gases). Radiation = by rays (even through space).

Flash cards · Tap to turn over

Important words

First say what the word means, then turn the card over.

Test yourself · Part 2

True or false?

Read the question and the answer. Is the answer right? Tap True or False.

    Now the real quiz!

    The quiz has many more questions on this topic. Every question shows straight away whether you are right and explains why.

    Take the quiz: Energy and heat transfer
    All Grade 7 Natural Sciences summaries
    For parents
    • Read one part together and ask your child to tell it back in their own words.
    • The ticks (“I know this”) are saved on this device only. We never ask for names or emails.

    Follows CAPS for Grade 7 Natural Sciences. Always check your teacher’s notes and textbook too.

    Free PDF