Free PDFGrade 5 · Science · 35 min
Ghost flame
Why does a flame have almost no shadow, but its smoke does?
I can explain why some things make a shadow and others do not.
A science experiment video with a free worksheet and answer key for teachers
About the video
In the video a torch shines through a candle flame onto a wall, and the flame casts almost no shadow while the smoke does. At home your child sets up a candle 30 cm from a white wall in a dark room, holds a torch 1 m behind it and compares the shadows of the holder, the flame and the smoke.
Solid things block light and make dark shadows, but a flame is mostly hot gas that lets light through, and it makes its own light too. Smoke is millions of tiny particles that block and scatter light, so it leaves a grey shadow.
What your child learns
- Explain why solid things make dark shadows
- Compare dark, faint and almost invisible shadows
- Describe how smoke particles block and scatter light
What's on the worksheet
- 1Predict first
- 2Shadow check
- 3What did you see?
- 4The science behind it
- 5Match the words
- 6Light through or blocked?
- 7True or false
- 8Shadow maths
- 9Draw the wall
You need
1 candle in a holder, 1 strong torch or phone light, 1 white wall (or a white sheet of paper taped to a wall), matches and an adult.
Safety
Only an adult lights and blows out the candle. Keep paper at least 30 cm from the flame. Do not touch the hot wax.
Tip for the adult
Make the room as dark as possible and look for the faint wavy shimmer above the flame, which is hot air bending the light.
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