An unlit match contains approximately 1,000 J of chemical energy. When it burns, the match releases thermal energy and light energy. After it has burned, the remaining match contains 250 J of chemical energy. If the thermal energy was measured to be 400 J, how much light energy did the match emit?

350J

Explanation:

Based on the first law of thermodynamics, which is the law of conservation of energy, energy can neither be created nor lost but can only be transformed. This implies that energy input of a system must equate the energy output as no energy can be lost.

In this case regarding an unlit match that contains 1000J of chemical energy. It burns to emit light energy and heat/thermal energy. If the amount of emitted thermal energy measured is 400J and the remaining/left over amount of chemical energy is 250J, this means that the missing amount of energy has been emitted as light energy.

To find the amount of light energy emitted, we say;

Amount of chemical energy - (thermal energy emitted + remaining chemical energy)

= 1000 - (400 + 250)

= 1000 - 650

= 350J

Hence, the amount of light energy emitted is 350J. This satisfies the law of conservation of energy because the output energy is equal to the total energy in the system.