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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Food Energy Content Practical
Food provides us with energy to carry out our daily activities. But how do we measure exactly how much energy different foods contain? In this practical, we'll explore how to measure the energy content of food samples using a simple calorimeter setup. This is a key practical for understanding how the food we eat fuels our bodies.
Key Definitions:
Food energy measurements help us understand:
This practical is based on the principle that when food burns, it releases chemical energy as heat. By capturing this heat and measuring the temperature change in water, we can calculate how much energy was stored in the food sample.
A food calorimeter is a simple device that allows us to measure the energy released when a food sample burns. The heat from the burning food is transferred to water and we measure the temperature increase.
1. Measure 100ml of water using a measuring cylinder
2. Pour the water into the metal can
3. Record the initial temperature of the water
4. Weigh your food sample
5. Mount the food sample on a needle or paperclip
1. Light the food sample
2. Position it under the can
3. Allow it to burn completely
4. Stir the water gently
5. Record the highest temperature reached
6. Weigh any unburnt food remains
• Always wear safety goggles
• Use a heat-proof mat
• Keep hair tied back
• Have water nearby to extinguish flames
• Never leave burning food unattended
Once you've collected your data, you can calculate the energy content of your food sample using the following steps:
To calculate the energy released by the food sample:
If you burned 1.2g of peanut and the water temperature rose from 20°C to 45°C:
A class conducted the food energy content practical with different food samples and obtained these results:
They noticed that foods with higher fat content generally released more energy per gram. This aligns with our understanding that fats provide about 37 kJ/g, while carbohydrates and proteins provide about 17 kJ/g.
Like all scientific experiments, the food calorimeter has limitations that affect the accuracy of results. Understanding these can help us improve our experimental design.
Understanding food energy content is crucial for human nutrition. Our bodies need energy for basic functions (basal metabolism), physical activity and growth. The energy we consume in food should ideally match our energy requirements.
Different people have different energy requirements based on factors like:
For example, a teenage boy might need around 2,750 kcal per day, while a teenage girl might need around 2,100 kcal per day. Athletes and very active people need more energy than those who are sedentary.
Food manufacturers use sophisticated bomb calorimeters to determine the energy content of their products. This information appears on food labels, usually in kcal (kilocalories) and kJ (kilojoules).
When you see that a chocolate bar contains 250 kcal, this means it will provide your body with 250 kcal of energy. If you were to burn it in a perfect calorimeter, it would release the same amount of energy as would be needed to heat 250 litres of water by 1°C.
Food labels help consumers make informed choices about their energy intake and maintain a balanced diet.
The food energy content practical is a hands-on way to explore how different foods store chemical energy. Though our simple calorimeter isn't as accurate as professional equipment, it demonstrates the scientific principles behind measuring food energy and helps us understand why different foods provide different amounts of energy to our bodies.
Remember that while high-energy foods like fats are often considered less healthy in large amounts, all food types play important roles in a balanced diet. The key is understanding energy content so we can make informed choices about what and how much we eat.
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