The diagram below shows a hand warmer. It uses a controlled burn of a type of lighter fluid called naphtha.

Question

The device has a refillable reservoir that holds the naphtha liquid. The fuel moves into a glass fiber burner, which absorbs the fuel and allows it to burn slowly without producing a flame. Oxygen reaches the burner through the holes on the cap at the top of the device. As the fuel is burned, heat is conducted to the metal casing of the device.

When the hand warmer is tested, it becomes too hot and uncomfortable to hold. How could the device be modified to solve this problem?
A.
by replacing the glass fiber burner with a material that does not soak up liquid fuel
B.
by increasing the size of the fuel reservoir so that it can store more liquid fuel
C.
by attaching a covering to reduce the amount of oxygen entering the device
D.
by using a fuel that is more flammable than naphtha so that the fuel can be used faster

Answer 1

To solve the problem of the hand warmer becoming too hot and uncomfortable, the best modification would be:

A. by replacing the glass fiber burner with a material that does not soak up liquid fuel.

This option would limit the amount of fuel that is burned at any given time, reducing the overall heat output and making the device more comfortable to hold. The other options would either increase fuel availability, increase combustion speed, or restrict oxygen, which could worsen the overheating issue rather than alleviate it.