Answers - PSLE

Pg 124 Q1
(a) When Cup Y is heated, its volume increases when it expands but its mass remains the same.

(b) The air above the flame gains heat from the flame and hot air rises, pushing cup Y up.

Pg 129 Q6
(a) Five objects

(b) No. Light from the light source will not be blocked by the object.

(c) Move the objects closer to one another.

Pg 130 Q7
(a) When light is completely locked by an opaque object or partially blocked by a translucent object, a shadow is formed.

(b) She is walking away. At the start of period Y, Daisy is directly below the lamp and her shadow is the shortest. Then she starts moving away from the lamp and her shadow becomes longer.

(c) The length of her shadow took 4 seconds to decrease from 3m to 0.5 m i the first part of the graph but it took 2 seconds to increase from about 0.5m to 3m in Period Y.

Pg 133 Q10
(a) Different metals expand at different rates when heated.

(b) Less than 201mm. More heat is needed to heat the thicker rod for it to expand to 210 mm.

(c) It would buckle. .When the metal bridge gains heat from the sun and expands, it will expand. If there are no gaps, there is no space for the bridge to expand.

Pg 143 Q20
(a) As the time decreases, the temperature of the water decreases.

(b) The temperature of the water in set-up A decreases more slowly than set-up B.

(c) Air is a poor conductor of heat. The person will lose less heat to the cold surroundings.

Pg 148 Q 25
(a)It reflects light from the furthest distance from Zainal.

(b) It is to ensure that the results are more accurate.

Note:
Why does xx do the experiment three times?
To REDUCE experimental errors so that the results will be more RELIABLE and CONSISTENT.