Simple Tests

Question 1

Test for lipids:

Answer 1

Ethanol emulsion test.
If substance is solid, crush it first.
If lipids are present, there will be a cloudy white substance on the surface of the water.

Question 2

Test for proteins:

Answer 2

Biuret test.
Color change in proteins: blue to violet
Color change in peptides: blue to pink

Question 3

Test for starch

Answer 3

Iodine test.
To prep leaves, boil it in water for 30 seconds. Then boil in ethanol for 2 minutes to remove chlorophyll (to prevent color mixup). Finally, rinse and wash the leaf before adding iodine.
Change: brown to blue-black

Question 4

Importance of a ‘control’ in an experiment

Answer 4

• to validate the results of the experiment
• to compare between the outcome from optimal conditions and the outcome from conditions being tested during the experiment

Question 5

Test for reducing sugars:

Answer 5

Benedict's reagent.
Heat solution and mix reagent.
If reducing sugars are present, color change:
- greenish/yellowish if low conc.
- red if high conc.