Lower Block Science – Revision (ANSWER KEY)

Q	Answer
1	a) Both give birth to young alive. b i) A b ii) C
2	a) to provide warmth to the eggs b) the eggs are not fertilised.
3	2
4	4
5	3
6	1
7	1
8a) 8b)	Both plants have weak stems. The plants need to climb up the supports to be able to maximise the absorption of sunlight (1m).
9a) 9b)	The larger surface area allows the leaves to get more sunlight to make food.          Chlorophyll is still present for photosynthesis but hidden among the red pigments.
10	4
11	2
12	2
13a)	Period B.   Compared to period A, the increase in the length of his shadow was greater / faster over 2 seconds. [1m] OR The rate of increase in the length of his shadow was higher in period B than period A. (Must compare the difference in the rate at which the shadows in different periods changed in length. 13b)      He was walking towards the lamp. His shadow became shorter.
14	4
15	3
16 (a)	Rod Z could be a magnet.
16 (b)	Distance A will decrease.
16 (c)	The heat on the magnet will cause it to lose some of its magnetism, thus making the repulsion weaker.  This will cause Rod Z to move closer to it.
17	3
18	(a) Pupils should label at the 60 ml mark of the cylinder. (1m) (b) A solid’s volume does not change with a change in its shape. (1m)
19 (a)	When the flask was heated, it also heated up the air inside it, which caused the air to expand [½m] and move out through the glass tubing [½m].  The air escaped through the water in the beaker as air bubbles.
19 (b)	The water in the beaker would move up the glass tubing./ The water level in Beaker A decreased.
19 (c)	After the flask has cooled down, the air inside would contract [½m].  This would create more space in glass tubing [½m].  Thus, the water in the beaker would move up the glass tubing to take up the space.
19 (d)	Flask B did not have a stopper [½m], which thus allowed heated air to escape from the flask through its opening and not through the glass tubing [½m].  Thus, no air bubbles were formed this time.
20(a)	Y has a rougher texture than X
20(b)	Material X has a smooth texture and hence it has less friction between body and bench [½m]. It is dangerous to sit at Point A as the boy may slip off the bench [½m]
21	(a)  X : Digestive system Y : Muscular system (b) The muscles at the gullet help to push the food (1m) down to stomach. / The muscles at the mouth help to chew the food (1m) to allow the food to be swallowed. / The muscles near the anus help to push out the waste materials (1m) out of the body.
22	1
23	4