ENERGY FROM FOOD Year 7 ScienceEarth’s Resources

Aim To burn a sample of food and calculate its energy content.

Materials•food samples such as: rice cracker, potato chip

•cork

•aluminium foil

•paper clip

•retort stand and clamp

•thermometer

•test-tube

•electronic balance

•small measuring cylinder

Method

1 Using the measuring cylinder, carefully measure 10 mL of water. Pour it into the test-tube.

2 Cut a small piece of your first food sample. Record its mass in your table.

3 Set up the equipment as shown in the diagram so that the food sample will sit about 2 cm below the test-tube.

4 Measure and record the initial temperature of the water using the thermometer.

5 Use a match to set the food sample alight, and then carefully place the burning sample under the test-tube.

6 When the sample stops burning, measure the final temperature of the water and record this result.

7 Repeat the activity using two other food samples.

Results 1 Copy the results table below into your workbook.

Table 1: Change in temperature

2 Calculate the change in water temperature by subtracting the initial temperature from the final temperature. Record your results in Table 1.

3 For each sample, divide the change in water temperature by the mass of the sample. Record your results in Table 1.

Results 4 Using a sheet on graph paper, draw a bar graph to show the change in water temperature/mass of sample using the data from your table.

Your graph must include the following:

•Labels (x and y axis)

•Title

•Use appropriate scale

•Legend

•Accurate data points

•Presentation

Results 5 Copy the results table below into your workbook.

Table 2: Energy stored in sample

6 It takes 4.2 joules of energy to raise the temperature of 1mL of water by 1◦C. So to calculate the heat energy gained from 10mL of water, multiple the temperature rise by 42. The answer will be in joules. Calculate the energy used to heat water (J) for each food sample. Record your results in Table 2.

7 Calculate the estimated energy stored in each food sample (J/g) by dividing the energy used to heat the water by the mass of the sample. Record your results in Table 2.

Energy used to heat water (J)

Energy stored in each sample (J/g)

Results 8 Using a sheet on graph paper, draw a bar graph to show the energy stored in each sample using the data from your table.

Your graph must include the following:

•Labels (x and y axis)

•Title

•Use appropriate scale

•Legend

•Accurate data points

•Presentation Discussion Compare the different samples and list them in order from the one that contains the most energy per gram to the one that has the least energy per gram.

Conclusion “Refer back to aim” talk about the energy content in food