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Grade 9 Intermediate About 20 min Version 1 Awaiting review Premium

Radiation: black cans and shiny cans

Heat can travel in three ways. Conduction passes it through solids, convection carries it in moving liquids and gases, and radiation sends it as infrared waves that need no material at all; that is how the Sun's heat crosses empty space to reach us. When radiation hits a surface, some is absorbed and some is reflected. Dull, dark surfaces absorb radiation well and also give it off (emit it) well. Shiny, silvery surfaces reflect most radiation and are poor absorbers and poor emitters.

What you will learn

  • Name the three ways heat is transferred.
  • Compare how black and shiny surfaces absorb radiation.
  • Compare how black and shiny surfaces emit radiation.

Before you start

  • Read a thermometer.

Materials

  • Two identical cans, one painted matt black and one shiny silver
  • Water at room temperature and hot water at 80 °C

Equipment

  • Two thermometers and a stopwatch

Procedure

  1. Put the matt black can of cool water in the sun and record its temperature every 5 minutes up to 20 minutes.
  2. Repeat with the shiny silver can.
  3. Fill each can with hot water at 80 °C, let it cool for 20 minutes and record the temperature.

How this simulation is simplified

  • The room is at 25 °C and the sunlight is steady. Both cans also lose some heat to the air by convection.