Problem 3 - Chemistry An Atoms First Approach

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.

Step-by-Step Solution

Answer

Striking a match generates heat through friction, converting potential energy into kinetic energy as thermal energy. The subsequent exothermic reaction ignites the match, transferring heat to the crumpled paper. As the paper and logs burn, endothermic and exothermic reactions occur, with potential energy transforming into thermal and light energy. This energy transfer heats up the system (fireplace) and surroundings, increasing their kinetic energy. In summary, potential and kinetic energy transformations, along with endothermic and exothermic reactions, are involved in igniting a fire and heating the environment.

Step 1: Striking the match

The action of striking the match causes friction between the matchstick and the striking surface. This friction creates heat, which converts some of the matchstick's potential energy (stored in the chemicals in the match head) into kinetic energy in the form of thermal energy.

Step 2: Igniting the match

When enough heat is generated, the chemicals in the match head undergo an exothermic reaction. In this reaction, the chemical potential energy is converted into kinetic energy as the released heat ignites the match.

Step 3: Lighting the crumpled paper

The burning match head is then used to light the crumpled paper. The heat energy (kinetic energy) from the match is transferred to the paper's molecules, raising their temperature and speeding up their motion. When enough heat is absorbed by the paper, it reaches its ignition temperature, and the paper begins to burn, converting its potential energy (stored in the chemical bonds) into kinetic energy in the form of thermal energy.

Step 4: Endothermic and exothermic reactions in burning paper and logs

As the burning paper heats up the logs, their temperature also increases, and their molecules absorb energy, causing an endothermic reaction. When the logs reach their ignition temperature, they start to burn and release energy through an exothermic reaction. This chemical potential energy is converted to thermal energy (kinetic energy) in the form of heat and light.

Step 5: Heating the system and surroundings

The heat energy released by the exothermic reaction of burning logs flows through the system (fire in the fireplace) and is transferred to the surroundings (the room, walls, and objects around the fire), increasing the temperature in the environment. This energy transfer increases the kinetic energy of the molecules in the surroundings, resulting in a rise in temperature in the entire room.

Step 6: Emitting light energy

In addition to producing heat, the burning fire also emits light energy that illuminates the surroundings. This radiant energy is also a form of kinetic energy, as it results from the motion of the excited particles in the system. In conclusion, the process of igniting a match and starting a fire involves several energy transfers, involving potential and kinetic energy and both endothermic and exothermic reactions. The chemical potential energy stored in the match head, paper, and logs is converted into kinetic energy in the form of heat and light, heating both the system and its surroundings.