GCSE Biology required practical activity: Food tests
Using qualitative reagents to test for a range of carbohydrates, lipids and proteins
Risk assessment
Safety goggles should be worn when carrying out the tests.
Wash off spills on skin immediately.
Take care with boiling water.
Method
You are provided with the following:
food to be tested
a pestle and mortar
a stirring rod
filter funnel and filter paper
2 beaker, 250 ml
a conical flask
2 test tube
Benedict’s solution
iodine solution
kettle for boiling water
a thermometer
safety goggles.
Read these instructions carefully before you start work.
1. Use a pestle and mortar to grind up a small sample of food.
2. Transfer the ground up food into a small beaker. Then add distilled water.
3. Stir the mixture so that some of the food dissolves in the water.
4. Filter using a funnel with filter paper to obtain as clear a solution as possible.
The solution should be collected in a conical flask.
5. Half fill a test tube with some of this solution.
6. Add 10 drops of Benedict’s solution to the solution in the test tube.
7. Put hot water from a kettle in a beaker. The water should not be boiling.
Put the test tube in the beaker for about five minutes.
, 8. Note any colour change.
If a reducing sugar (such as glucose) is present, the solution will turn green, yellow, or brick-red. The
colour depends on the sugar concentration.
9. Take 5 ml of the solution from the conical flask and put it into a clean test tube.
10. Add a few drops of iodine solution and note any colour change.
If starch is present, you should see a black or blue-black colour appear.
11. Record your results in a table such as the one below.
Using qualitative reagents to test for a range of carbohydrates, lipids and proteins
Risk assessment
Safety goggles should be worn when carrying out the tests.
Wash off spills on skin immediately.
Take care with boiling water.
Method
You are provided with the following:
food to be tested
a pestle and mortar
a stirring rod
filter funnel and filter paper
2 beaker, 250 ml
a conical flask
2 test tube
Benedict’s solution
iodine solution
kettle for boiling water
a thermometer
safety goggles.
Read these instructions carefully before you start work.
1. Use a pestle and mortar to grind up a small sample of food.
2. Transfer the ground up food into a small beaker. Then add distilled water.
3. Stir the mixture so that some of the food dissolves in the water.
4. Filter using a funnel with filter paper to obtain as clear a solution as possible.
The solution should be collected in a conical flask.
5. Half fill a test tube with some of this solution.
6. Add 10 drops of Benedict’s solution to the solution in the test tube.
7. Put hot water from a kettle in a beaker. The water should not be boiling.
Put the test tube in the beaker for about five minutes.
, 8. Note any colour change.
If a reducing sugar (such as glucose) is present, the solution will turn green, yellow, or brick-red. The
colour depends on the sugar concentration.
9. Take 5 ml of the solution from the conical flask and put it into a clean test tube.
10. Add a few drops of iodine solution and note any colour change.
If starch is present, you should see a black or blue-black colour appear.
11. Record your results in a table such as the one below.
