Lesson 5 energy and food
Aim – Calculate the energy content of two different brands of crisp
5 minutes – recap of the last two lessons about renewable energy and fossil fuels.
This lesson is has two parts – In the first part discuss and identify our energy related need for food. In the second part is an experiment.
10 minutes Starter Living things such as people transform the energy provided by food into other forms
We need heat to maintain our body temperature. Energy from food is transformed into movement including the movement needed to make our lungs breath air and our heart pump blood. The food we eat combines with oxygen to make the energy.
If we eat more than we need the food is converted into fat.
You need to remember that humans convert the chemical energy from food into movement (kinetic) energy and heat energy.
Some types of food provide more energy than others. The energy content of food can be measured in units called Joules. If you throw an apple about 1 metre into the air then you use up about 1 Joule of energy.
30 minutes Main activity and experiment
Comparing the energy content of two different types of crisp
Measure out 10 ml of water and pour it into a boiling tube.
Carefully place the tube in a clamp stand.
Use a thermometer to record the starting temperature of the water.
Carefully light the crisp using a Bunsen burner and hold underneath the boiling tube.
Once the crisp has extinguished record the finishing temperature of the water.
The specific heat capacity of water is approximately 0.42 Joules/g. We can work out the energy content of each crisp by using the equation…
Energy content = temperature change of water x 42 (10 grams of water)
Megan and Georgina's energy content = 19 x 42 = 798
Energy content of 100g of crisps = Energy content/mass of wotsits x 100.
Megan and Georgina's energy content of crisps = 798 Joules / 1.5 grams x 100 = 53,200 Joules
Do our results agree with what the food labels on the crisps say?
According to the label a 100g of Wotsits contain 2,270,000 Joules.
What!?! So where did all the energy go? Thats what we will be finding out in the next unit 'Heating and Cooling'.
Grading
Level 4
List the eight forms of energy
Level 5
Describe some energy transfers including some which involve living things
National curriculum links
Sc4 5a Energy resources
Sc1.2g- observations
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