Q&A - PSLE Science

[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.

[verykiasumummy]

J and J:

verykiasumummy:

[quote=\"Zhu99\"][

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.[/quote]

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

oh no... i didnt see the question correctly... the mass is weighed together with the test tube... i thought only weigh the leaves... that's why i had explained it differently..

if weigh the plant together with test tube, then ans is 3. cos water does not get evaporated because of the oil, and does not leave the plant thru its stomata.. so yes, answer is 3...

pardon me...

[unclelee]

The leaves trap air, thus air cannot pass in or out easily.

[paranoid]

http://i48.tinypic.com/24268ll.jpg\">


Answer key says 2 but my answer is 3...please help :?:
Thanks in advance.

[NY1969]

I think your ans is correct. Given all conditions remains the same, the only variable is the direction of the light bulb.

[charsen]

Bottle Gardens

A really attractive and unsual way of growing plants indoors is to create a bottle garden. If carefully made a bottle garden can last a long time needing very little attention and with great advantage that the plants do not get dusty and pest, draughts and fumes are excluded. Select a suitable glass container with a lid. The more air tight the lid the less watering the plants will need.
(abstract from: http://www.greenchronicle.com/gardening/bottle_gardens.htm)
Based on the information from the abstract above, explain how the plants in the bottle garden can last a long time with little watering.
Given answer in the assessment paper :
When the plants transpire, water is given out in the form of water vapor. This water vapour will condense on the cool surface of the glass container to form water droplets. The water droplets will flow back into the soil to moisten it.
Can this be explained with an alternative answer?
The plants have a controlled transpiration. As the bottle is air tight, the water vapour in the air gets saturated with transpiration by plants after sometime. Hence the rate of transpiration will be slower thus retaining the water for a longer period of time

[charsen]

paranoid:

http://i48.tinypic.com/24268ll.jpg\">


Answer key says 2 but my answer is 3...please help :?:
Thanks in advance.

The answer 2 is correct I think. The aim is to check if the plant grows towards light. Independant variable should be the position of the light source. Change the position of the light source and see if the plant grows towards different directions. Option 3,4 is crossed out as it deals with brightness of bulb which is not the aim. Option 1 does not say anything about bulb A, C in Set up Y. Hence the answer should be 2, with which position of the bulbs are varied with 2 set up.