Convection (C+20)

  C+20+0 Heat water in "O" shaped tube adding a dye.
  C+20+5 Crooke's radiometer with flashlight, arc lamp or IR source.
  C+20+10 Cardboard strip drawn from glass tube extinguishes candle.
  C+20+15 Hot air balloon: Dry cleaner bag over Bunsen burner rises to ceiling.
  C+20+20 Applet: Balloons & Buoyancy