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 attaching a covering to reduce the amount of oxygen entering the device
C.
by using a fuel that is more flammable than naphtha so that the fuel can be used faster
D.
by increasing the size of the fuel reservoir so that it can store more liquid fuel

Answer 1

To solve the problem of the hand warmer becoming too hot and uncomfortable to hold, the best option among the provided choices is:

B. by attaching a covering to reduce the amount of oxygen entering the device.

Explanation:

• The heat produced by the hand warmer is a result of the controlled burning of naphtha, which requires oxygen. By reducing the amount of oxygen available to the burner, the combustion process will slow down, leading to less heat produced and thus preventing the hand warmer from becoming excessively hot.

The other options are less effective at addressing the overheating issue:

• A would likely increase the amount of fuel available for burning, thus exacerbating the overheating problem.
• C would allow the fuel to burn faster, which could create more heat output and aid in overheating.
• D increases the fuel supply but does not address the issue of excessive heat generation.

Thus, option B is the most effective modification to control the heat output of the hand warmer.