Question

Carlos was camping and getting cold as the sun went down. He wanted to light a fire for warmth and light. However, he discovered that the nearby wood was wet, and would have no light. He had to look under some leaves and debris to find dry wood. He piled the wood and surrounded it with a circle of stones to keep the fire contained. Then he put some dry leaves around the logs to help the fire to get started. He lit the leaves. Soon the leaves had burned away, his fire was burning nicely, and Carlos was getting warmer.
1. Is the chemical reaction produced by Carlos's fire exergonic or endergonic?

2. Is the reaction in Carlos's fire endothermic or exothermic? Explain

3. Do you think the leaves were a catalyst for the fire? Why or why not?

Answer 1

1. The chemical reaction produced by Carlo's fire is exergonic because energy is "going out". As the reaction proceeds, entropy increases as the energy stored in the dry wood and leaves are used up as fuel to create the fire which produces low quality light and warmth.  

2. This reaction is a classic example of an exothermic reaction. Exothermic reactions are characterized with the presence of heat and light in the products. Combustion reactions are always exothermic in nature.

3. Catalyst are substances that are used to speed up reactions by lowering the activation requirement. Catalysts aren't consumed in the reaction and can still be chemically retrieved afterwards. In this situation, the leaves cannot be retrieved after the reaction ends. The leaves speed up the heating of the wood but it does not behave as a catalyst.