Observation

Many candidates answered this question, while some did quite well, others performed badly.
In (a),some candidates were able to explain the evidence that photosynthesis occurred in a green leaf while some candidates merely explainedthe experiment that it is done in the laboratory to test for starch and that starch is a product of photosynthesis.

In question (b), some candidates were able to name the gases involved in photosynthesis but could not state the source of the gases named.

In question (c), some candidates could not explain the reason a newborn baby’s food is in liquid form but a few candidates could. Also many candidates were able to name food substances present in breast milk.

Questions (d) was a poorly answered question, as most candidates could not state explain the food test well.

The expected answers are:

• (a)  Evidence that photosynthesis has occurred in a green leaf
• The presence of starch in a green leaf indicates that photosynthesis has occurred/taken place;
• the starch is usually tested using iodine solution; the leaf is boiled in hot water;
• then decolorized by placing in hot alcohol/ethanol using water bath;
• the decolorized leaf is washed with hot water;
• and placed on a white tile;
• add a few drops of iodine solution;
• the leaf turns blue black;
• indicating the presence of starch.

(b)  (i)  Gases involved in photosynthesis on a sunny day

• Oxygen;
• Carbon (IV) oxide/carbon dioxide.                                             

Note: spelling must be correct to score.

(ii) Source of each of the gases mentioned above
Oxygen - produced by plant after photosynthesis/photolysis of water;
Carbon (IV) oxide/carbon dioxide – obtained from respiration/exhalation by animals/plants/living things/putrefaction/decaying of organic matter/atmosphere.                                                                                                                                    
(c)  (i)  Reasons newborn baby’s food is always in liquid form

Water is needed for digestion;

and a newborn baby’s digestive system is not fully developed/functional;

a baby does not also have teeth to chew solid food.

  
(ii)  Food substances in breastmilk

• water
• proteins
• carbohydrates
• vitamins
• mineral salts
• fats/oils/lipids

(d) How Biuret test would be carried out on egg white solution

• Put (2cm3) egg white solution in a test tube;
• Add (1cm3) sodium hydroxide/bench solution;
• Shake the content thoroughly;
• Add 1% Copper (II) sulphate in drops;
• Shake after each drop;
• Colour will change to violet/purple;
• Showing the presence of protein.