Science Applications Set A

Qn	Answer	Remarks/Explanation
14a	Heat travels from a warmer place to a cooler place. When he applied alcohol on his forearm, his warmer forearm loses heat to the alcohol. The alcohol gains heat and vaporizes. He felt the cooling sensation because the part of his skin lost heat to the alcohol.	When explaining, always try to give : (1) comparison, if there is (2) relevant concept (3) link back to the question
14b	The temperature will drop. Heat travels from a warmer place to a cooler place. Joseph’s tea will lose heat to the cooler alcohol so the temperature drops.	When explaining, always try to give : (1) comparison, if there is (2) relevant concept (3) link back to the question
15a	Blood vessel B has thicker walls than blood vessel A. Blood vessel A has a tissue that prevents blood from flowing backwards, but blood vessel B does not.
15b	Blood vessel B. It has thicker walls which can withstand the high pressures from the fast flowing blood pumped from the heart.
16a	The travellator. The plant transport system comprises of 2 separate set of tubes that moves up and down the plant.
16b	Heart
17a	A and B / AB
17b	The heat from the surroundings
17c	Mark on the y axis any where between -10 to 0.
19	(1)	There is no way a question like this will appear in the PSLE. It is too tedious.
20	(4)
21	(4)
22a	Photosynthesis
22b	Light, Water, Carbon dioxide and nitrogen
22c	When the tree is young, it is not as tall. Thus it is near the forest floor where there is less light. The leaves need to be bigger so that it can trap more sunlight. When the tree is grown, it is taller and thus the leaves are found in the area where there is more light, so the leaves become smaller.
23a	Heat the air in flask X over a flame. OR Cool the air in flask Y will some ice.	Be specific. Don’t just say heat or cool the air.
23b	Matter expands when heated. When the air in flask X is heated, it expands and move up the tube, pushing the ink drop towards Y. OR Matter contracts when cooled. When the air in flask Y is cooled, it contracts. Thus there is more space in the tube causing the ink drop to move towards Y.	When explaining, always try to give : (1) comparison, if there is (2) relevant concept (3) link back to the question
24	(4)
25a	Highest – Gold Lowest – Silver
25b	Aluminium. It has a lower melting point than iron, thus it would be easier to melt the aluminium to make it into the cans.
26	(1)
27	(4)
28	(1)
29a	Join the left dot to dot 1. Joint the right dot to dot 4.
29b	Eliza can control the same lamp from 2 different locations. The 2nd switch allows her to switch off the light from on top of the stairs after she has walked up. Otherwise, she will have the climb the stairs in darkness.
31a	Draw B between the Y axis and line for A.
31b	The air in container A and container B will gain heat from the lamp. The clear plastic sheet will prevent some heat from escaping from the opening thus more heat is retained in container B. This causes the temperature to rise faster than air in container A.	When explaining, always try to give : (1) comparison, if there is (2) relevant concept (3) link back to the question