Q&A - PSLE Science

[P5G]

Please help.


Q1. Which one of the following illustrates the correct sequence in which plants lose excess water through the leaves?

(1) Root hairs –> leaf veins –> xylem vessels –> stomata

(2) Root hairs –> xylem vessels –> leaf veins –> stomata

(3) Root hairs –> stomata –> xylem vessels –> leaf veins

(4) Root hairs –> leaf veins –> stomata –> xylem vessels




Q2. The diagram shows the side view of water molecules exiting a stoma.

Why do plants have to waste all these water that they take in?

A: To prevent the plants to uptake nutrients.

B: To allow the plant to be cooled down as the water evaporates.

To allow carbon dioxide to enter the leaves.

To allow the plants to take in even more water.


(1) All except A.

(2) All except B.

(3) All except C.

(4) All except D.



Q3. Which direction does the food (sugars) manufactured in the leaves flow?

(1) Up only

(2) Down only

(3) Up and down only

(4) Up, down and sideways


TIA.

[Dbdad]

Hi Everyone,


I have a couple question. I need help.

Q1) What happens when the ribcage moves in and downward?

Q2) Description of the cells that were studied under the microscope are listed below.
a) They have large nuclei
2) They have cytoplasm
3) They have large number of chloroplasts ]

2a) Which of the following were the samples of the cells taken?
a) Cheeks cells b) Stem of the balsam plant c) Feather from a sparrow
d) Leaf of lily pad e) skin if an earthworm f) Yeast cell

Which one of the above description helps you make your decision?

Thanks in advance.

DB

[starlight1968sg]

Dbdad:

Hi Everyone,


I have a couple question. I need help.

Q1) What happens when the ribcage moves in and downward?

Q2) Description of the cells that were studied under the microscope are listed below.
a) They have large nuclei
2) They have cytoplasm
3) They have large number of chloroplasts ]

2a) Which of the following were the samples of the cells taken?
a) Cheeks cells b) Stem of the balsam plant c) Feather from a sparrow
d) Leaf of lily pad e) skin if an earthworm f) Yeast cell

Which one of the above description helps you make your decision?

Thanks in advance.

DB

Hi,
My answers are no guaranteed to be correct!

2) (d) The presence of chloroplasts means the sample contains chlorophyll.

[tianzhu]

Hi


For Q1, please refer to the primary science textbooks and PSLE Science Guide Book (Marshall Cavendish).There are detailed explanations.

As for Q2,in the Unit of Life. students learnt that about parts of a cell. I shall not elaborate here as they are detailed in the science textbooks and PSLE science Guide book.

Chloroplasts contain a green pigment called chlorophyll which helps plants to capture sunlight to make food.
Therefore, option (a), and (e) are offside.

Lily pads are floating leaves; hence option (d) is the right choice.

Best wishes

[tianzhu]

Hi


Most of the water which travels upwards is lost from the leaves through pores called stomata - a process called transpiration.Transpiration helps to cool a plant due to evaporation.
The transport system in plants is made up of two kinds of tubes
•\txylem to transport water and minerals.
•\tphloem to transport manufactured food.
Water and mineral salts are absorbed through the roots by a force called transpiration pull.

For Q1 ---- The answer is option (2).
For Q2 ----- The answer is option (1).
For Q3 ----- I would go for option (4).Manufactured food by leaves is transported to all parts of the plant — buds, flowers, fruits, roots and storage organs. I’ve included sideways because of upwards/downwards in stem and branching out sideways to buds, flowers, etc.

Please let us have the answers when you receive them from your teacher.

Best wishes

[tianzhu]

James Ang:

I reasoned that the correct answer is (3) and not (1) for the below reasons;


1. Water vapour escape from the surface of the water rather than from the bottom of the container. (kinetic particle theory - where the active particles leave the surface of the liquid and become gas, leaving the remaining particles to have less average energy per particle)
2. Water contains dissolved air which is necessary for the survival of living things that live in water. Boiling will expel the dissolved air from the water. That's why water animals cannot live in boiled water that has cooled down as the water does not contain dissolved oxygen.

I am sure the above reasons are convincing and scientific for you.

Hi P5G

Let’s us revisit this question again.

My answer is same as you .It is water vapour. James has a different answer.
Have you checked with your science teacher? For the benefits of PSLE 2010 kiasu kids, please let us know the correct answer.

Best wishes

[tianzhu]

atutor2001:

Ask farmers, \"How to plant carrots?' and they will tell you to use seeds.


Ask a Singapore PSLE student the same question and they will tell you to use a carrot.

Both are right.

However, planting carrot using carrot doesn't make sense because we will get back the same carrot, perhaps a bigger one after some time (but the carrot will be too old). Technically speaking we are growing back the old plant so I don't think it is really a reproduction process. So if we really need to show that carrot can reproduce from its roots, we should use only the top part of the carrot (the bottom part of the carrot can be our meal).

Hi atutor2001

I agree with your first statement. However for the second one, I’ve my reservations. From the highly popular PSLE Science Guide, first edition (MC), pg 133, students learned that carrots are grow from seeds.I think the revised second edition has included vegetative propagation as a form of reproduction for carrots.

We can grow carrots from cutting the top of an existing carrot.However,this method is not frequently used.

http://www.doityourself.com/stry/different-carrot-propagation-methods

Best wishes

[P5G]

tianzhu:

Hi P5G


Let’s us revisit this question again.

My answer is same as you .It is water vapour. James has a different answer.
Have you checked with your science teacher? For the benefits of PSLE 2010 kiasu kids, please let us know the correct answer.

Best wishes

My personal notes after discussions with my Science teacher.

Before boiling -- Air bubbles (air dissolved in the water)

During boiling - Water bubbles (water in the gaseous state, that is water vapour)

When water is heated to 100 degree C -- it refers to before boiling. So Worksheet answer is correct.
(Time when water is below 100 degree C to 100 degree C)

Confusion - 100 degree C.

Hope that my personal notes are accurate and correct and are useful to all.

[tianzhu]

P5G:

My personal notes after discussions with my Science teacher.

Before boiling -- Air bubbles (air dissolved in the water)

During boiling - Water bubbles (water in the gaseous state, that is water vapour)

When water is heated to 100 degree C -- it refers to before boiling. So Worksheet answer is correct.
(Time when water is below 100 degree C to 100 degree C)

Confusion - 100 degree C.

Hope that my personal notes are accurate and correct and are useful to all.

Hi P5G

Thank you for your quick reply.

You’ve brought up a very interesting point regarding the definition of when.

We are given the understanding that
When water is heated to 100 degree C -- it refers to before boiling.

This means water has not reached its boiling point of 100 degree C according to your discussion with your teacher.
Should we interpret it in this way? I am not so sure, maybe, some members who are more proficient in English may help to clarify?

Best wishes

[P5G]

tianzhu:

Hi P5G


Thank you for your quick reply.

You’ve brought up a very interesting point regarding the definition of when.

We are given the understanding that
When water is heated to 100 degree C -- it refers to before boiling.

This means water has not reached its boiling point of 100 degree C according to your discussion with your teacher.
Should we interpret it in this way? I am not so sure, maybe, some members who are more proficient in English may help to clarify?

Best wishes

The water is heated to 100 degree C, its boiling point.

According to my teacher to see water bubbles, we need to continue to supply heat. The heat will be used to change water from liquid to gaseous state. It also explains why the temperature remains at 100 degree during boiling.