Cooking and food additives

Question 1

Recognise that a chemical change takes place if:

Answer 1

• there is a new substance made
• the process is irreversible
• an energy change takes place

Question 2

Explain why cooking food is a chemical change:

Answer 2

• a new substance is formed

* the process cannot be reversed

Question 3

Relate types of food additive to their function:

Answer 3

• antioxidants stop foods from reacting with oxygen
• food colours give food an improved colour
• flavour enhancers improve the flavour of a food
• emulsifiers help oil and water to mix and not
separate.

Question 4

Explain how baking powder helps make cakes rise

Answer 4

when baking powder is heated, it breaks down to release carbon dioxide. The gas makes cake rise.

Question 5

Test for carbon dioxide

Answer 5

bubble gas through limewater, limewater goes cloudy

Question 6

Explain why the texture of egg or meat changes when

it is cooked:

Answer 6

shape of protein molecules permanently changes.

Question 7

Explain why potato is easier to digest if it is cooked:

Answer 7

• cell walls rupture resulting in loss of rigid structure
and a softer texture
• starch grains swell up and spread out.

Question 8

Explain why an emulsifier helps to keep oil and water

from separating:

Answer 8

• hydrophilic end bonds to water molecules

* hydrophobic end bonds with oil or fat molecules.

Question 9

Construct the balanced symbol equation for the

decomposition of sodium hydrogencarbonate

Answer 9

2NaHCO3 → Na2CO3 + CO2 + H2O

Question 10

Recall the word equation for the decomposition of

sodium hydrogencarbonate

Answer 10

sodium hydrogen→ sodium + carbon + water

carbonate carbonate dioxide

Question 11

Describe emulsifiers

Answer 11

molecules that have a water
loving (hydrophilic) part and an oil or fat loving
(hydrophobic) part.

Question 12

when do the protein molecules in eggs and meat change shape

Answer 12

when eggs and meat are cooked: this

is called denaturing