Holt 10.4 Questions 1-3

1. Why do fluffy down comforters provide more warmth than thin cloth blankets?

They trap more air. Air is a good insulator.

2. Explain how conduction causes the surface of a bridge to freeze sooner than the road surface on either side of the bridge.

The road surface on either side of the bridge is in contact with the ground below it. The ground is a good conductor compared to air. The thermal energy from the ground is conducted to the road, making it cool slower than the bridge, which is in contact with air below it which does nothing to warm the bridge.

3. If you place a heavy piece of canvas on top of a down sleeping bag, you will later feel colder than if you were to place the sleeping bag on top of the canvas. Explain why this happens. (Hint: A large amount of air is present in an uncrushed sleeping bag.)

The air in the sleeping bag is a good insulator. Your body’s thermal energy is not conducted away very fast when next to a good insulator. When you place the heavy canvas on top of the sleeping bag, you squeeze the air out of the sleeping bag, causing it to be a better conductor. So heat from your body conducts into the air more rapidly.