Section 2 - Human Nutrition P2

Question 1

Describe a practical where you can test the amount of energy there is in different types of food:

Answer 1

1) you need dry food that’ll burn easily
2) weigh a small amount of food and then skewer it on a mounted needle
3) add a set amount of water to a boiling tube held with a clamp this is to measure the amount of energy produced
4) measure the temperature of the water and light your food with a Bunsen burner, make sure the Bunsen burner isn’t near your tube so that it doesn’t affect your results
5) immediately hold the burning food under the boiling tube until it goes out, then relight th food and hold it under again do this until it won’t catch fire
6) then measure the temperature of the water again

Question 2

What’s the equation for calculating the amount of energy in joules?

Answer 2

Energy in food(J)=mass of water in g X temperature change in water°C X 4.2

1g=1cm3
4.2 is the amount of energy needed to rise the temperature of water by 1°C

Question 3

What’s the equation for calculating the amount of energy per gram?

Answer 3

Energy in food(J)
Energy per gram of food(J/g)=———————————
Mass of food(g)

Question 4

Why do you need to calculate the amount of energy per gram?

Answer 4

To be able to compare the foods fairly

Question 5

How can the accuracy of the testing energy in food experiment be increased?

Answer 5

• experiment isn’t perfect quite a lot of heat is lost to the surroundings
• insulating the boiling tube e.g. With foil, would minimise heat loss and keep more energy in the water making your results more accurate