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Christian Alliance Cheng Wing Gee College
S4 Biology Practical Worksheet
Name: _____________________________ ( ) Class: ________ Date: _______________
Practical 5.1 Detection of food substances by food tests
In the space below, write down the procedures of all the following food tests:

Results
A Test for glucose using Clinistix paper
Sample
Clinistix paper

Original colour
Final colour
Glucose solution

Distilled water

B Test for reducing sugars using Benedict’s test
Sample
Mixture of Benedict’s solution and sample

Observable change
Glucose solution

Distilled water

C Test for starch using iodine test
Sample
Iodine solution

Original colour
Final colour
Starch solution

Distilled water

D Test for lipids using grease spot test
Sample
Presence of translucent spot after drying?

Before immersing into organic solvent
After immersing into organic solvent
Cooking oil

Egg white solution

Distilled water

E Test for proteins using Albustix paper
Sample
Albustix paper

Original colour
Final colour
Egg white solution

Distilled water

F Test for vitamin C using DCPIP solution
Sample
DCPIP solution

Original colour
Final colour
Vitamin C solution

Boiled vitamin C solution

Distilled water

Questions:

1. Do the amount of samples used in food tests need to be measured very accurately?

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2. Why is a boiling water bath preferred to a Bunsen flame for heating up the mixture of glucose solution?

3. How does the