Experiment 6 (Reducing heat loss)

How does a thermos flask stop hot water from cooling down?

• A thermos flask
• A thermometer
• Hot water

(Implied by the aim) The thermos flask will keep the hot water hot for a long time.

1. Look at the outside of the thermos flask. What is it made of?
2. Take off the lid. What is the lid made of?
3. Carefully take apart the flask to see the inside. What color is the inside part?
4. Put the thermos flask back together.
5. Pour hot water into the thermos flask.
6. Use the thermometer to measure the water's temperature and write it down.
7. Close the lid tightly.
8. Wait for one hour.
9. Use the thermometer to measure the water's temperature again and write it down. What do you see?

• The outside of the thermos flask is made of plastic or metal.
• The lid is made of something that doesn't let heat pass through easily, like plastic or wood.
• The inside of the flask has a shiny silver surface.
• The hot water stayed hot for more than one hour.

• This experiment shows that a thermos flask stops heat from escaping.
• The materials it's made of (plastic, silver, and a space with no air) help stop heat from moving out of the flask.