When looking around supermarkets, we see a variety of foods and drinks. We need to consume food and drink to ensure we have the energy for our daily activities, such as:
Energy can be transferred between different stores, but it is never lost. Food and drinks contain chemical energy. Energy is often measured in calories (kcal), but the scientific units are joules (J) or kilojoules (kJ).
The food we consume provides us with the energy that enables our body to function. The amount of energy in different foods can be found on their outer packaging, on food labels. These food labels provide us with information about the food’s nutrients, which include fat, carbohydrates and salt.
Below is an example of this:
The energy section is shown on the label of the food item above. Each 150g serving of this food contains 1046 kJ of energy, which is the same as 250 kcal.
One calorie is the energy needed to raise the temperature of 1 g of water by 1 °C
Keep in mind, the energy listed might not be for all the food. For example, in the food label above, the energy listed is for each 150 g serving.
Different activities require different amounts of energy. For example:
Running might use up to 3500 kJ per hour
Resting might use up to 350 kJ per hour
Sleeping might use up to 300 kJ per hour
Fuels, such as oil, gas, coal, and wood, store energy. Both food and fuels contain chemical energy.