Q&A - PSLE Science

[atutor2001]

WS1234567:

atutor2001:

[quote=\"WS1234567\"]The timing is not important in such answers.

However, the question is very specific : \"What is the aim of the experiment?\" the answer given must be \"sure correct one\" (based on the facts given). How are we to know for sure that the person is interested in finding out how well the soil will absorb water?

To know the aim of the experiment, we actually need to know what the person is measuring at the end of the experiment.

The soil that is better able to absorb water will not allow all the water to be flow out of it so quickly, thus giving a timing that is slower.[/quote]Thank you

[leesf]

Hi, will appreciate help on the following 2 questions. Thanks


Q1) Which of the following is wrongly stated?
A) Both plants and animals can move
B) Both plants and fungi cannot move
C) All plants, animals and fungi release carbon dioxide
D) Both fungi and animals depend on other living for nutrition.

1) A
2) B
3) C
4) D

Ans : 2

Reason being although plants cannot move from one place to another, they can respond by growing towards light.

I just like to confirm the above answer and explanation is correct as we always have the concept that plants cannot move.


Q2) Four painted tins were placed under the sun. A thermometer was inserted into each tin. After 30 minutes, the temperature of each tin was recorded
Tin A - painted black, Tin B - painted silver, Tin C - painted white, Tin D - painted brown
Which tin will have the lowest temperature reading?

Ans : Tin B

I thought answer should be white as white will reflect heat and will not be able to absorb heat as much as silver.

[youngtay]

Hi,


Can anyone explain to me for question 4,why is the answer (2)?

http://www.orlesson.org/orp/09Sc/2009-Sc-CA1-MahaBodhi.pdf


TIA

[Muffins]

Hi Youngtay, it's 2 because:


for A1, freezing does not take up heat from the surroundings, so cross that out.

For A3, Evaporation does change the state of a substance, from loiquid to gaseous, so cross that out.

For A4, Freezing does not require heating, so cross that out.

Using the simple yet effective elimination method, you can figure out that the answer is A2.

[meimeitan]

Hi! All,


May i know:

three batteries are arranged in series in a curcuit set-up and with a blub. One of the batteries is used up energy, then will be the blub still lit up?

thanks.

meimeitan

[leesf]

Hi, appreciate if you could help on the following.

http://postimage.org/image/73y2cr9g/


a) What would she observe on the inner surface of the bell jar in set-upA after one day?

b) Explain clearly your answer in (a),

c) How can she improve on her experiment to show that water vapour is lost mainly through the leaves of plants?

Thanks

[the kiasu student]

leesf:

Hi, appreciate if you could help on the following.

http://postimage.org/image/73y2cr9g/


a) What would she observe on the inner surface of the bell jar in set-upA after one day?

b) Explain clearly your answer in (a),

c) How can she improve on her experiment to show that water vapour is lost mainly through the leaves of plants?

Thanks

My answers:

a) She would observe tiny water droplets.

b) The water from the soil in the pot in set-up A evaporated into water vapour, the water vapour touched the cooler inner surface of set-up A and condensed on it.

c) She should use a plastic bag to warp up the pot in both set-ups to prevent any water from the pot from evaporating. She should also remove any other moisture left in the set-up before the experiment.

May not be right, but that is how i would answer it. :celebrate:

[Tang]

leesf:

Hi, appreciate if you could help on the following.

http://postimage.org/image/73y2cr9g/


a) What would she observe on the inner surface of the bell jar in set-upA after one day?

Water droplets

b) Explain clearly your answer in (a),

Water vapour evaporated from the moist soil and condensed into water droplets when it touched the cool inner surface of the bell jar.

c) How can she improve on her experiment to show that water vapour is lost mainly through the leaves of plants?

She should cover the pots with plastic bags, with a hole just right for the stem to go through, to prevent water in the soil from evaporating into the bell jars.


Hi,

My answers are in bold.

Thanks

[Tang]

meimeitan:

Hi! All,


May i know:

Three batteries are arranged in series in a circuit set-up and with a bulb. One of the batteries is used up energy (flat), then will be the bulb still light up?

Yes, as there are two batteries working.

But this is bad for operation, as the flat battery may leak and spoil the equipment.

thanks.

meimeitan

[atutor2001]

leesf:

Q2) Four painted tins were placed under the sun. A thermometer was inserted into each tin. After 30 minutes, the temperature of each tin was recorded
Tin A - painted black, Tin B - painted silver, Tin C - painted white, Tin D - painted brown
Which tin will have the lowest temperature reading?

Ans : Tin B

I thought answer should be white as white will reflect heat and will not be able to absorb heat as much as silver.

If we can create a perfect white body, then it will reflect all heat. However, the \"white\" we have is imperfect and will absorb some heat.

Silver can reflect more heat than \"imperfect white\" because it contains pigments (not in Pr syllabus) that helps to reflect heat. So silver will reflect more heat than \"imperfect white\".