OB4 read and interpret the energy values indicated on food product labels and compare the energy content per 100 g of a number of foods, and identify the food types on the label that form part of a balanced diet.

Quite simply, Guideline Daily Amounts (GDAs) can be used to take the guesswork out of what we should be eating, making planning a healthy balanced diet much easier.

Take control of your sugar, fat and salt intake

The GDA for calories for an average adult is 2000.

A calorie is the amount of Energy that is required to raise the temperature of 1g of water by 1oC. This is not a lot of energy so usually people talk in Calories as opposed to calories. 1 Calorie = 1000 calories, have you noticed the difference between Calories and calories ??

The GDA for sugars for an average adult is 90g.

The GDA for fat for an average adult is 70g.

The GDA for saturates for an average adult is 20g.

The GDA for salt for an average adult is 6g.

contents of a variety of food products as described on their labels

List out the values of 3 foods of your own choice

OB5 investigate the conversion of chemical energy in food to heat energy

MandPractivity Practical Activity 2

investigate the conversion of chemical energy in food to heat energy


  1. Warm the piece of food to be burned.
  2. Using a beaker to support an empty test tube on a mass balance, find the mass of the glassware
  3. Add water to the test-tube, about 25g of water
  4. Find the Initial (starting) temperature of the water, keep the thermometer in the water do not take it out. (why not?)
  5. Get the mass of the piece of food that you will burn.
  6. Check the temperature of the water again, make sure it is the same as the 1st reading
  7. Light a piece of food and hold it under the test tube and by turning it make sure that it all burns.
  8. As soon as the flame goes out re-read the temperature of the water


Mass of crisp = g

mass of empty test tube = g

mass of test tube + water = g

mass of water = g

starting temperature of water = oC

final temperature of water = oC


This Formula is how we can find out the energy that went into the water.

m = mass of water

c = the specific heat capacity of the water,

this is a constant value it does not change, it is 4.2Jg-1oC-1

or 4180 J/kgC

T = change in temperature of the water.

If we find these 3 values & multiply them out

we find the energy given off by the food.

If we divide this answer by the mass of the food

we get the energy per gram.

This is a convienient value, of Joules per gram but it might be very small,

we usually will see the energy per 100g,

so multiply the value you got by 100

Now compare the value you got to the one printed on the back of the packet.

the chemical of food energy


Find out more here