Question

A fire is started in a fireplace by striking a match and lighting crumpled paper under some logs. Explain all the energy transfers in this scenario using the terms exothermic, endothermic, system, surroundings, potential energy, and kinetic energy in the discussion.

Short answer

In this scenario, the system is the match, crumpled paper, and logs, while the surroundings are the fireplace and room. When the match is struck, friction provides kinetic energy to the chemicals on the match head, converting it into potential energy in an endothermic reaction. As the match ignites the paper, exothermic reactions occur, converting potential energy into thermal energy and light. The burning paper then transfers heat to the logs, causing them to ignite in another exothermic reaction. The logs' heat release warms the surroundings, further demonstrating the exothermic energy transfers taking place.

Step-by-step solution

Define the system and surroundings

In this scenario, the system consists of the match, crumpled paper, and logs. The surroundings include the fireplace and the room the fireplace is in.

Understand exothermic and endothermic reactions

An exothermic reaction is a chemical reaction that releases heat into the surroundings, while an endothermic reaction is one that absorbs heat from the surroundings. In the process of lighting a fire, we will identify which reactions are exothermic and which are endothermic.

Lighting the match

When the match is struck, the friction between the match head and the striking surface provides kinetic energy (K.E) to the chemicals on the match head. This kinetic energy converts into potential energy (P.E) stored in the chemical bonds of the match head. The reaction happening here is endothermic as it absorbs energy from the surroundings to go underway.

Match igniting the paper

When the match head burns, it undergoes an exothermic reaction, converting the stored potential energy of the chemicals into thermal energy (heat) and light. The released heat is then transferred to the crumpled paper, increasing the kinetic energy of the molecules in the paper until it catches fire.

Paper burning and igniting the logs

The burning of paper is also an exothermic reaction, with the potential energy stored in the molecular bonds of the paper being converted into thermal energy (heat) and light. This heat released warms the logs, increasing their kinetic energy and causing them to ignite, too. The combustion of logs is another exothermic reaction in which potential energy stored in the logs is converted into thermal energy (heat) and light.

Transfer of energy to surroundings

As the logs burn, they emit heat, which warms the surroundings, increasing the temperature of the fireplace and the room. This transfer of heat into the environment is a classic example of an exothermic reaction, where energy is released into the surroundings. Overall, we observe several energy transfers in this situation - from kinetic to potential energy, and from potential energy (in the form of chemical bonds) to kinetic and thermal energy (through exothermic reactions).