Q&A - PSLE Science

[jewelbox]

Here is the other qn. thanks. http://i45.tinypic.com/280uu8h.jpg\">

[PSLE student]

jewelbox:

Here is the other qn. thanks. http://i45.tinypic.com/280uu8h.jpg\">

The first answer is 3, while the second answer is 2. READ the question CAREFULLY!! It says, \" After 3 days,.....\" Thus the decrease in mass must be big. So, it is E and H.

[charsen]

jewelbox:

Hi, need help on 2 qns attached. Both my ans are 3 but both ans given are 2. Thanks.

http://i48.tinypic.com/jt2jqo.jpg\">

Hi
Circuit A has its batteries and its bulbs arranged in parallel
as same amount of eletric current flows through each bulb and the brightness
remains the same.

The disadvantage of bulbs in parallel is that it lasts for a shorter time since the bulbs are in series.
Hence,the answer should be 3 and never 2.

Circuit B has both the batterires and the bulbs in series.The electric current flown through each bulb is the same but the brightness is lower than before.
Charsen

[Nebbermind]

PSLE student:

jewelbox:

Here is the other qn. thanks. http://i45.tinypic.com/280uu8h.jpg\">

The first answer is 3, while the second answer is 2. READ the question CAREFULLY!! It says, \" After 3 days,.....\" Thus the decrease in mass must be big. So, it is E and H.

The plants coated with oil will have least water loss, ya?
Shouldn't it be 3?

[verykiasumummy]

Nebbermind:

PSLE student:

[quote=\"jewelbox\"]Here is the other qn. thanks. http://i45.tinypic.com/280uu8h.jpg\">

The first answer is 3, while the second answer is 2. READ the question CAREFULLY!! It says, \" After 3 days,.....\" Thus the decrease in mass must be big. So, it is E and H.

The plants coated with oil will have least water loss, ya?
Shouldn't it be 3?[/quote]the leaves coated with oil cannot photosynthesise, cannot exchange gases, so will shrivel up, hence will have greater mass loss.

[Zhu99]

jewelbox:

Hi, need help on 2 qns attached. Both my ans are 3 but both ans given are 2. Thanks.

http://i48.tinypic.com/jt2jqo.jpg\">

The correct answer is 3. The bulbs in Circuit A are arranged in series, so more current is drawn from the batteries. Hence the life span of the batteries in Circuit A is shorter than that in Circuit B.

[Zhu99]

jewelbox:

Here is the other qn. thanks. http://i45.tinypic.com/280uu8h.jpg\">

The correct answer is 3. The water loss for F and G are lower, hence their leaves are coated with oil, so transpiration (loss of water through stomata) could hardly take place.

[shell]

DD needs help with this question –

Qn: Why is air stagnant in leaf litter habitat ?


many thanks, shell

[verykiasumummy]

Zhu99:

jewelbox:

Here is the other qn. thanks. http://i45.tinypic.com/280uu8h.jpg\">

The correct answer is 3. The water loss for F and G are lower, hence their leaves are coated with oil, so transpiration (loss of water through stomata) could hardly take place.

based on your explanation, it means all other plants w/o leaves coated with oil will continue to become smaller and lighter in mass due to water loss?

no, it should be 2. leaves coated with oil cannot exchange gases (true that it will have less water loss), but it cannot photosynthesize (make food will increase its mass). so means after 3 days, it would be deprive of food, hence explain the great mass loss..

just sharing my views, i dun mean to pinpoint anything.

[J and J]

verykiasumummy:

Zhu99:

[quote=\"jewelbox\"]Here is the other qn. thanks. http://i45.tinypic.com/280uu8h.jpg\">

The correct answer is 3. The water loss for F and G are lower, hence their leaves are coated with oil, so transpiration (loss of water through stomata) could hardly take place.

based on your explanation, it means all other plants w/o leaves coated with oil will continue to become smaller and lighter in mass due to water loss?

no, it should be 2. leaves coated with oil cannot exchange gases (true that it will have less water loss), but it cannot photosynthesize (make food will increase its mass). so means after 3 days, it would be deprive of food, hence explain the great mass loss..

just sharing my views, i dun mean to pinpoint anything.[/quote]The plant itself will produce carbon dioxide as it respires also in both day and night. It's only during the daytime the rate of photosynthesis is faster than its rate of respiration, so needs to take up carbon dioxide from external sources. So after 3 days, it may not be deprive of food but restrict its growth.
So I think the water loss due to transpiration is a better reason for the mass.