← Back to the activity

Grade 7 Science — Heat transfer in nature

Tell conduction, convection and radiation apart by what the particles do, explain land and sea breezes, and follow water from the sea to an aquifer.

Name: ________________________

Before you start

Four pins are stuck along a metal strip with wax, and one end of the strip is heated. Here is the strip, pin by pin.

1234
  1. 1. Pin I
  2. 2. Pin II
  3. 3. Pin III
  4. 4. Pin IV

The heat travels along the strip from the heated end towards the cold one, melting each blob of wax as it arrives. Pin I sits nearest the flame and Pin IV farthest away, so the pins drop one after another in that order. The strip itself has not moved anywhere — just the heat has.

  1. 1.Match each way of transferring heat to what the particles are doing.

    • Conduction
    • Convection
    • Radiation
    • the heated particles themselves move, carrying the heat
    • heat passes along, and the particles stay where they are
    • heat crosses with no medium to carry it

  2. 2.Groundwater levels in many towns are falling. Which pair of causes does the chapter give?

    • a) Rainfall stopping altogether, and rivers changing course
    • b) Heavy extraction for a growing population, and concrete surfaces that leave less room for water to soak in
    • c) Aquifers turning to solid rock, and wells being dug too shallow
    • d) Too much rainwater harvesting, and too many recharge pits

  3. 3.Rain, snow and hail are three forms of the same stage of the water cycle. What is the word that covers them together?

  4. 4.An underground layer of sediment and rock that holds water in its pore spaces, and that a bore well is drilled into, has a name. What is it?

  5. 5.Why is light-colored clothing more comfortable in summer?

    • a) It reflects most of the heat falling on it, while dark surfaces absorb more
    • b) It lets sweat evaporate faster than dark cloth does
    • c) It conducts heat away from the body faster than dark cloth
    • d) It is made of thinner cloth than dark clothing is

  6. 6.Two thin blankets keep you warmer than one thick one. What does the chapter give as the reason?

    • a) Two blankets weigh more, and weight holds heat in
    • b) The outer blanket reflects heat back through the inner one
    • c) Thin cloth is woven more tightly than thick cloth
    • d) Air is trapped between them, and air is a poor conductor of heat

  7. 7.In conduction, what happens to the particles of the material the heat is crossing?

    • a) They travel from the hot end to the cold end, carrying the heat
    • b) They break apart and re-form further along
    • c) They stop moving, which is what makes the material feel hot
    • d) They stay where they are and pass the heat to their neighbors

  8. 8.Sort each material by how readily it lets heat pass through.

    Groups: Good conductor of heat · Poor conductor of heat

    • Wood
    • Glass
    • Air
    • Aluminum
    • Steel
    • Clay

Answer key — Grade 7 Science — Heat transfer in nature

  1. 1. Conduction → heat passes along, and the particles stay where they are; Convection → the heated particles themselves move, carrying the heat; Radiation → heat crosses with no medium to carry it
  2. 2. b) Heavy extraction for a growing population, and concrete surfaces that leave less room for water to soak in
  3. 3. precipitation
  4. 4.
    • aquifer
    • an aquifer
    • aquifers
  5. 5. a) It reflects most of the heat falling on it, while dark surfaces absorb more
  6. 6. d) Air is trapped between them, and air is a poor conductor of heat
  7. 7. d) They stay where they are and pass the heat to their neighbors
  8. 8. Steel → Good conductor of heat; Aluminum → Good conductor of heat; Wood → Poor conductor of heat; Glass → Poor conductor of heat; Clay → Poor conductor of heat; Air → Poor conductor of heat