Light without heat

The idea

Bioluminescence is the production of light without heat in living organisms, which happens through a chemical change.

Two lights

On a dark evening, a candle burns and a firefly glows. Both give out light.

Which of them also gives out heat?

• Only the firefly
• Only the candle
• Both of them

Heat or no heat?

Light the candle and watch the firefly. Each light has a heat bar. Does it fill?

Bioluminescence

Fireflies are insects that give out light in gardens and fields in the late evening. Their light is produced by a chemical change.

The production of light without heat in living organisms is called bioluminescence.

• Light from | Heat given out? | It is a
• A burning candle | yes | chemical change
• A firefly | no | chemical change

Notes

Bioluminescence is the production of light without heat in living organisms. Fireflies make light by a chemical change.

Check yourself

Which of these shows bioluminescence?

Bioluminescence is the production of _ in living organisms.

The light of a firefly is produced by a _.

What is true for both a candle and a firefly?

• A burning candle. A candle gives out heat as well as light.
• Burning magnesium ribbon. It gives out a dazzling light and also heat.
• A glowing firefly — correct. Yes! A living insect makes light without heat.
• light together with heat. That is what burning gives out. Bioluminescence has no heat.
• light without heat — correct. Yes! It is light without heat.
• heat without light. Bioluminescence is about light.
• chemical change — correct. Yes! The light is produced by a chemical change.
• physical change. The light of a firefly comes from a chemical change.
• no change at all. Something has to change to make the light. It is a chemical change.
• Both give out heat. A firefly gives out light without heat.
• Both give out light — correct. Yes! Both give out light.
• Both are living things. A candle is not a living thing.