BIOLOGY
PAPER 3
POST MOCK – 2021
MARKING SCHEME
a) .
Food substance Procedure Observation Conclusion
Starch - Put 2cm3 of soln M Solution changes to blue Starch present; Rej.
into the test tube black; acc blue or black Negative form
- Add 2,3,4 drops of alone Acc presence of starch
iodine/dropwise/drop Acc changes from
by drop brown/yellow to
✓ 1 blue/black or black or
blue
Reducing sugars - Put 2cm3 of soln M Blue colour retained Reducing sugars
into the test tube absent;
- Add equal amount of ✓ ✓
Benedict’s soln
- Heat to boil
b) (i) .
Food substance Procedure Observation Conclusion
Starch As above Colour of iodine persists; Starch absent
✓ ✓
Reducing sugars As above Blue colour of Benedict’s Little amounts
changes to green or Or
yellow/brown/orange Presence of reducing
✓ sugars
✓
✓ Don’t award for procedure, already awarded in a
PAPER 3
POST MOCK – 2021
MARKING SCHEME
a) .
Food substance Procedure Observation Conclusion
Starch - Put 2cm3 of soln M Solution changes to blue Starch present; Rej.
into the test tube black; acc blue or black Negative form
- Add 2,3,4 drops of alone Acc presence of starch
iodine/dropwise/drop Acc changes from
by drop brown/yellow to
✓ 1 blue/black or black or
blue
Reducing sugars - Put 2cm3 of soln M Blue colour retained Reducing sugars
into the test tube absent;
- Add equal amount of ✓ ✓
Benedict’s soln
- Heat to boil
b) (i) .
Food substance Procedure Observation Conclusion
Starch As above Colour of iodine persists; Starch absent
✓ ✓
Reducing sugars As above Blue colour of Benedict’s Little amounts
changes to green or Or
yellow/brown/orange Presence of reducing
✓ sugars
✓
✓ Don’t award for procedure, already awarded in a
