Question

A thin paper cup filled with water will not catch the fire when it is placed over a flame. The reason for this is
A. water cuts off the oxygen supply to the paper cup
B. water is an excellent conductor of heat
C. the paper cup will not become appreciably hotter than the water it contains.
D. water is a poor conductor of heat

Answer 1

Hint: The ignition point is defined as the fire point, which is the point at which the fuel gets fired. That means the possible least temperature at which the vapour of a fuel is continuing the burning for a minimum of five seconds after the ignition by an open flame having standard dimensions. Any substance will catch fire only when the ignition point I reached. This may help you to solve this question.

Complete answer:
A thin paper cup which is filled with water will not catch up the fire if it is placed over a flame. This is because the paper cup does not become appreciably hotter than the water it carries.
If the paper cup is heated carrying water, the water will be absorbing the heat coming from the burning source and thus stops the paper from reaching its ignition point. Therefore it will not burn. Instead of this, water in the cup becomes hot. This is because of the absorption of heat by water in it.

So, the correct answer is “Option C”.

Note:
Even Though the water carrying paper cups will not catch fire in a flame, this won’t be true if it is placed in a microwave. Paper cups are made to hold hot drinks and food, but it cannot withstand the extreme heat of a microwave. This will cause the paper cups to get leaked.