burning food

 

(a) Calculate how much energy was absorbed by the water.

The formula for calculating heat absorbed is:

$$\text{Heat} = \text{mass of water} \times \text{temperature change} \times 4.18 \, \text{J/(g°C)}$$

• Mass of water: 50 mL = 50 g (density of water is 1 g/mL)
• Temperature change: Final temperature $-$ Initial temperature (recorded during the experiment)

For example, if the temperature of the water rose from 25°C to 45°C:

$$\Delta T = 45 - 25 = 20 \, \text{°C}$$ $$\text{Heat} = 50 \, \text{g} \times 20 \, \text{°C} \times 4.18 \, \text{J/(g°C)} = 4180 \, \text{J}$$

Energy absorbed by the water = 4180 J

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(b) Where did this energy come from?

The energy absorbed by the water came from the combustion of the nut. The burning nut releases stored chemical energy as heat, which is transferred to the water.

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(c) Calculate the amount of heat produced per gram of fuel (nut) burned.

To calculate heat produced per gram of the nut:

$$\text{Heat per gram} = \frac{\text{Heat absorbed by water}}{\text{Mass of nut burned}}$$

If the mass of the nut burned was 0.5 g:

$$\text{Heat per gram} = \frac{4180 \, \text{J}}{0.5 \, \text{g}} = 8360 \, \text{J/g}$$

Heat produced per gram of nut = 8360 J/g

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(d) Compare combustion to digestion of the nut.

Aspect	Combustion of Nut	Digestion of Nut
Reactants	Nut + oxygen (O₂)	Nut + enzymes
Products	CO₂, H₂O, heat energy	Glucose, fatty acids, energy
Total Energy Production	Releases energy quickly as heat	Releases energy slowly for bodily functions
Energy Storage	No storage; all energy is released	Energy is stored as ATP in cells
Efficiency	Low efficiency, energy is lost as heat	High efficiency; energy stored for use

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(e) Sources of Experimental Error and Improvements

Sources of Error:

1. Incomplete combustion of the nut (not all energy released).
2. Heat lost to the surroundings instead of being absorbed by the water.
3. Measurement inaccuracies in mass, temperature, or water volume.
4. Variability in nut size or energy content.

Improvements:

1. Use an insulated setup to minimize heat loss to the environment.
2. Ensure complete combustion by using a controlled oxygen supply.
3. Use a digital thermometer and more precise measuring tools.
4. Perform multiple trials and average the results for accuracy.

Let me know if you'd like further clarifications! 😊