Why is it so cold up there?
Physics Age group: KS3: atmosphere and changes of state
Planes cruise where the air is far below freezing. What does that do to their exhaust?
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Live data for the board
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Worksheet: Why is it so cold up there?
Name: ______________________ Date: ____________
Use the live board for this worksheet.
- The air cools by about 2 °C every 1,000 ft. How cold is it at 35,000 ft if the ground is 15 °C?
- What is a contrail made of, and why does it form?
- Look at the sky above you. Do you see any trails? How long do they last, and what does that say about the air?
- Why does it matter that exhaust contains water vapour?
Class quiz
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Teacher notes and answers
Suggested answers. Many will vary with the live data, so check units and working. The curriculum links are a guide only.
- 15 − (35 × 2) = −55 °C (the real average is about −54 °C).
- Tiny ice crystals. The hot, damp exhaust meets very cold air and the water vapour condenses and freezes.
- Answers will vary. Long-lasting trails mean the air up high is damp; short ones mean it is dry.
- Burning fuel makes water vapour as well as carbon dioxide. The vapour is what freezes into the trail.
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