Question

Imagine a campfire on a cold day. At first, the temperature of each log is as cold as the air around it. A few hours after the fire has burned out, the temperature of the ashes will also be cold. But in between, when the fire is burning, the temperature of the logs and surrounding air is very hot. What is the source of this thermal energy? For the answer, begin by identifying the reactants and products for the overall chemical reaction of burning wood. Wood is mostly carbohydrates, the bulk of which is cellulose. Cellulose is made up of hundreds to thousands of glucose groups connectected by oxygen molecules. The chemical formula for cellulose is (C6H12O6)n, where n is the number of glucose groups. For more manageable models, carbohydrates will be modelled as glucose with a chemical formula of C6H12O6.

Answer 1

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Step-by-step explanation:

From the statement of the first law of thermodynamics, energy is neither created nor destroyed, but is transformed from one form to another.

Thermal energy is possessed by the hot air while the fire is burning. This thermal energy was obtained from the chemical energy stored in carbohydrates(cellulose) that is present in wood material. As the combustion proceeds, chemical energy stored in chemical bonds of the wood material converts into thermal energy (heat energy). The chemical reaction involved in the combustion of wood can be simplified as shown below; n represents the number of glucose units that combine to make up the cellulose present in the wood material.

nC6H12O6(s) + 6nO2(g) ===> 6nCO2(g) + 6nH2O(g)

n may even be as much as thousands of glucose units.