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Why does a paper cup filled with water NOT catch fire even when heated by a flame from below?
AWater reacts with paper to make it fireproof
BWater absorbs heat by conduction, keeping the paper below its ignition temperature
CPaper does not catch fire even when alone
DThe flame cannot touch the paper because of the water
Answer & Solution
Correct answer: B. Water absorbs heat by conduction, keeping the paper below its ignition temperature
As the flame heats the bottom of the cup, the heat is conducted away into the water (and used to warm/boil it). As long as water is present, the paper does not reach its ignition temperature, so it does not catch fire.
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