Question 1 Report
| container | temperature drop in 20 min / °C |
|---|---|
| glass beaker | 28 |
| metal can | 41 |
| plastic cup | 19 |
| vacuum flask | 3 |
The table compares how quickly the same mass of hot water cools in four containers left in the same room. Which container is the best insulator?
The correct answer is vacuum flask. The best insulator is the container that loses the least heat, and the vacuum flask drops only 3 °C in 20 minutes compared to 19 °C for the plastic cup, 28 °C for the glass beaker and 41 °C for the metal can. The vacuum between its double walls prevents heat loss by conduction and convection, and the silvered surfaces reduce radiation.
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