- Six Diligence 2010

Friday, October 1, 2010 ; Michelle's Questions

These are questions Michelle post and my answers are in red.

6A

Q7) Each ocean zone has a different amount of light. When you mean shadow, where is the shadow? if fish is at twilight zone, is the shadow as the surface of the dark zone?
I meant a blurry image of the fish. It's not really a shadow, sorry. There will be no shadow in a dark zone unless it's light from organisms.

Q10) The question wrote "In the above set-ups, A and B, bubbles of gas were seen rising in the water when the switches were turned on" What does it mean "bubbles"? How does it form?
Actually, the process is called electrolysis. It is a method to separate different elements like iron, calcium, oxygen, hydrogen, etc, in a liquid using electricity. The bubbles formed are actually the hydrogen and oxygen moving towards the two metal plates called electrodes. They move because of different charges (positive and negative) on the 2 electrodes. This is totally out of the syllabus. It's a very difficult sec 3 science concept. Just take the bubbles as "substances" removed from the solutions. In this case, it's hydrogen and oxygen.

Q23) I don't understand why is the answer 4 and not 2. (2) Herbivore (4) Scavenger?
It's actually not a scavenger but a detritivore. Herbivore is more for organism feeding on living plants or parts of plants. Scavenger feeds on corpse not killed by itself eg vulture. Detritivore feed on dead plants eg earthworm. The so-called best of the worst answer is (4). I think I'll accept (2) too as it involves plants.

Q30) When Pham put several marbles into the can, did he take out the can then put it in or just put in on top of the can? And how does it affect?
Whether he put it in or on top will not affect the total mass. So the force of gravity acting on the can has increased, pulling the can further downwards and caused the water level to rise as the can occupies space.

7A

Q7) Is it true that if there is not cell wall, it is definitely an animal cell?
Not true as yeast has cell wall too. Given the regular shape of both cells C and D, they are plant cells.

? ? ? ?What are parts of the fungi cell? Is is like animals?
Fungi cell is like an animal cell but with a cell wall. This is the basic shape of a yeast cell. Some fungi cell has large vacuole too. But it's not in your syllabus, neither is the shape of yeast cell.

Q9) To a certain extent, amount of carbon dioxide and light affects rate of photosynthesis. Does amount of water affect too?
Yes, but there's a limit to how much a plant can photosynthesise given a high amount of light. For water, the rate of photosynthesis also increases with water till a certain extent. Too much water can cause roots to start rotting.

Q17) You wrote "The more the spring is compressed, the higher the metal ball goes when the spring is released". When it is released, is it all EPE convert to KE, then the KE would convert to GPE when it goes higher? Does it mean that when it just started to move, the KE is highest?
KE is very high but not the highest. Both the GPE and KE get their energy converted from EPE. When the ball's going to hit the ground, then it's the highest. This is because GPE has converted to KE as the ball approaches the ground.

Q19) What caused the iron fillings to stay? <- asked by Yun LIng
Iron filings are in fine powder form. It's like asking how come pepper can get stuck at the test tube or how come dust gets stuck on the inside of the test tube.

Q23) Could temperature be above boiling point? Like ice below freezing point?
Yes, steam can be above 100 degree Celsius as it gains more heat.

Q26) The reason you wrote what strange. I think it is not because of whether nearest to water to decide which is dispersed by water, which is dispersed by animal. Could I write: Because if A is dispersed by water, the children plant should locate lower that A as the flow of river is downwards, and it could not travel upwards, but the second picture shows that the children plant A locates above adult plant A, so it is not likely to be dispersed by water.
I was thinking of possible A upstream. It is mainly because of how A is distributed along the banks of the river that makes it a very natural choice for dispersal by water.

Q27) Does wax and cork gains heat from electric heater too??
Not directly. More of wax gains heat from the metal plate and cork gains heat from the wax.

? ? ? ? ?Is it because of air that allows heat transfer? What allows heat transfer then?
Heat transfers through radiation, convection and conduction. You only need to know conduction whereby heat flows from a warmer object to a colder one.

Q29) If surface Y has more friction, then why take longer time to travel before it stops, even though it travels a shorter distance?
My answer is actually longer distance for X than Y, so X travels a longer distance. Y takes a longer time to travel a fixed distance, not stopping distance. Given a fixed time, say 3 seconds, X will travel further than Y, so the friction between trolley and surface X is lesser.

PSLE Science Q44) The ball should not travel further but travels to a lower height. I don't understand.?
Given a lower force, an object couldn't have travelled further. Furthermore, the height should also reduce. You cannot draw the ball beyond the horizontal distance of the original ball.

Others

Q1) A smooth surface and a similar surface with ups and downs along the way. Why the second surface cause more friction?
It's bumpy and rough, so increases friction.

Q2) When it's dark, our eyes adapts to the changes and then we can see more clearly. Why? And when a light is opened, why do our eyes feel uncomfortable?
Our pupil (in eye) has become bigger in the dark to try to absorb all possible light for us to see. To switch on light suddenly will allow a large amount of light to enter our eyes before the pupil becomes smaller. The sudden influx of light causes us to be "blinded" for a while.

Q3) Respiration: Oxygen+ Food -> Energy + Carbon Dioxide + Water

? ? ? ?Is it that after respiration, heat energy is then converted?
Heat energy is also converted from chemical potential energy. However, not all organisms can use food to convert to energy, eg crocodile.

Q4) Mangrove plants have breathing roots that stick out to the mud. These roots have tiny openings for absorbing oxygen from the air.

? ? ? ?Does leaves exchange gas too?
You mean roots? Yes, the roots do.

? ? ? ?Does other parts of the plant exchange gas too, besides leaves? (to all plants)
Yes, actually all parts of the plant, like roots and stem, do take in oxygen to respire but we focus mainly on leaves having gas exchange.

? ? ? ?Is there a gas transporing tube to transport oxygen to the leaves?
Yes, water-carrying tubes carry dissolved oxygen as well but that's not important.

Q5) Cactus has spines instead of leaves to cut down water loss through transpiration. How?
Spines are very tinny leaves. Small leaves mean small stomata, do less water loss through leaves.

Q6) Experiment shown that when salt is added to ice, the temperature decreased, but you cannot conclude that the meling point decrease, can you?
Melting point as based the change of state of matter from solid to liquid.

Q7) If a food e.g. bread is placed in the fridge and it moulds, how will spores land?
Spores are everywhere, just like dust. It's a matter of whether they have good conditions to grow.

Q8) The air we breathe out include water vapour. Where does it come from? And when the air we breathe goes to the lungs, ?does all air get taken in?
It comes from respiration at cells to use oxygen to covert food to energy. Water and carbon dioxide are produced during respiration.

Q9) How would amount of sunlight affect rate of transpiration?
The warmer it is, the higher the rate of transpiration.

Q10) "Electricity always tries to find the easiest path to the ground". What does it mean?
Did I write that? I don't know what it means too. I must have meant other things for "ground". Short circuit is not in the syllabus.

Q11) What is static electricity? Is it in syllabus?
Nope. It's better not to know static electricity.

Q12) (Plants) Why would rate of respiration decrease during the day? I thought more activities (Photosynthesis), higher rate of respiration?
I agree with you too. Did I write wrongly again?

Regards,
Mr Wan

posted by Allan at 11:03 PM

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