Page 36 - Biology Form Two
P. 36
Biology for Secondary Schools
(iii) Fats and oils dissolve in organic 6. Tabulate your results showing
solvents such as ether, chloroform, food sample tested, procedures,
acetone, and alcohol. observation and inference.
(iv) When water is added to a fat or oil Food
3. FOR ONLINE READING ONLY
that has dissolved in an organic sample Procedures Observation Inference
solvent, a white milky suspension tested
is formed. This is called an
emulsion.
(v) When fat is rubbed against paper, Questions
the paper becomes translucent. 1. Is the area of the piece of paper
(vi) In a mixture of water and oil, oil rubbed with seeds similar to the
takes up Sudan III dye to form unrubbed section of the paper?
a red layer or ring on the top, 2. What did you see after exposing
leaving the water clear. the paper to light?
(vii) Oils react with osmic acid and
stain black. 3. What other seeds can you use to
perform the grease spot test?
Activity 1.7 (a): Test for the presence
of lipids in groundnuts by the grease Activity 1.7 (b): Test for the presence
spot test of lipids in cooking oil by using Sudan
Materials III reagent
Groundnuts seeds and a piece of white
paper Materials
Sudan III reagent, 5 ml of cooking oil,
Procedure test tube, measuring cylinder (10 ml),
1. Peel the groundnuts seeds. and water
2. Rub the peeled seeds on a piece Procedure
of paper. 1. Pour 3 ml of water in the test tube
Expose the paper to light. followed by 2 mls of cooking oil.
4. Compare the part of the paper 2. Add 2 drops of Sudan III reagent
rubbed with seeds with the part in the mixture.
that was not rubbed. 3. Shake well the mixture.
5. Record what you see. 4. Leave the mixture for 3-5 minutes
to settle.
30 Student’s Book - Form Two
05/10/2024 15:36:20
BIOLOGY FORM 2 NEW.indd 30
BIOLOGY FORM 2 NEW.indd 30 05/10/2024 15:36:20
