REquired practical 4: Food tests

Question 1

How to test for starch?

Answer 1

• place a few cm^3 of the food solution in a test tube.

- add a few drops of iodine solution (an orange colour).

Question 2

What observation will you see in a test for starch which is positive?

Answer 2

the solution will turn a blue-black colour from orange.

Question 3

How to test for sugars (reducing sugars(e.g. glucose))?

Answer 3

• place a few cm^3 of the food solution in a test tube.
• add a few (10-ish) drops of Benedict’s solution (a blue colour).
• place test tube with the solution in a beaker and half will with boiled water.
• leave for around five minutes.

Question 4

What observation will you see in a test for sugars which is positive?

Answer 4

the solution will change colour based on the amount of sugar present from blue.

• green(small)
• yellow(more)
• brick-red(a lot)

Question 5

How to test for protien?

Answer 5

• place a few cm^3 of the food solution in a test tube.

- add a few drops of Biuret solution (blue colour).

Question 6

What observation will you see in a test for protien which is positive?

Answer 6

the solution will turn a purple-pink colour from a light blue.

Question 7

How to test for Lipids?

Answer 7

• place a few cm^3 of the food solution in a test tube.
• add a few drops of ethanol.
• place a bung on the top of the tube.
• shake vigourously.

Question 8

What observation will you see in a test for lipids which is positive?

Answer 8

the soulution will turn a cloudy white colour from colourless.