1

General Science / Why do leaves change colour?

« on: 27/02/2006 19:24:41 »

Why do leaves of some plants change colour in autumn? I know it's somthing to do with singlet oxygen affecting the chlorophyll in leaves but I can't remember exactly. If someone can help me out it will be great.

Angel

2

Chemistry / Nano-Kids

« on: 19/11/2005 09:12:57 »

I saw this on the web the other day. It's amazing what a bit of chemistry can do!

http://cohesion.rice.edu/naturalsciences/nanokids/

ref. Vol. 80 No. 4 April 2003 • Journal of Chemical Education

Angel

3

That CAN'T be true! / Barometer

« on: 09/12/2003 08:30:49 »

This is a story about a physic student.

He was doing an exam at the end of his physics degree and one of the question was "How do you measure the height of a skyscraper using a barometer?" This student wrote, "Tie a string onto the barometer and lower it from the top of the skyscraper and the height of the skyscraper is the length of the string plus the length of the barometer." And (not surprisingly) this student failed his physics exam!

But this student claimed there's nothing wrong with his answer so he wrote to the examiners who later reply, "The answer showed absolutely no understanding of physics at all. However we would like to meet you and ask for an oral response to the question."

During this student's oral exam, he gave another answer to the barometer question. He said, "You could stand on top of the skyscraper, drop the barometer and measure the time taken to reach the ground. Using the mass of the barometer, acceleration due to gravity and time taken to reach the ground, the distance travelled can then be calculated." [] The examiners were shocked. He went on, "Or better still, you could go to the janitor of the skyscraper and say he can have a new barometer if he can just tell me the height of this skyscraper" []

There are rumours saying that the physics student in this story was Neils Bohr who later got a Nobel Prize for Physic [^]

Angel

"Anyone who has never made a mistake has never tried anything new." -Albert Einstein

4

General Science / Pencil lead

« on: 04/11/2004 20:26:45 »

Hello~ I haven't been around for ages...the amount of work to do has got on top of me.

Anyone knows how pencil lead of different hardness (eg. 2B, B, HB....etc) are produced? I say hardness of pencil lead because if it's softer then more graphite will be left on the paper. Is this due to the % compositions of graphite in pencil lead? What other substances are also in pencil lead?

Angel

5

Physics, Astronomy & Cosmology / surrounding temperature

« on: 18/05/2004 08:16:45 »

Does temperature decrease or increase as you going away from the Earth's atmosphere?

Angel

6

Chemistry / Copper (II) complex ion

« on: 30/04/2004 19:14:23 »

This question has been bothering me a while now, maybe Jay can put my mind at rest.

Copper (II) ions form the blue hexaaqua ion with water, [Cu(H2O)6]2+. On adding excess ammonia the blue colour changes into a beautiful deep purple as the tetraammine ion forms, [Cu(NH3)4(H2O)2]2+.

Ligand substitution occurs, but why are only 4 H2O ligands are replaced and not all six?

Angel

7

Chemistry / Phase and state

« on: 26/04/2004 08:24:51 »

What's the difference between phase and state? And which terminology should be used?

Angel

8

Physics, Astronomy & Cosmology / About the Milkyway...

« on: 21/04/2004 08:27:57 »

How come we can see the Milkyway using an astronomical telescope when the Earth is actually in the Milkyway?

Of course the 'Milkyway' I'm referring to is the galaxy and not the chocolate bar! []

Angel

9

Physiology & Medicine / fish oil and other supplement overdose

« on: 10/03/2004 10:43:20 »

My mom is asking about the amount of fish oil capsules, vitamin E and calcium you can have in one day. Is it OK to take one capsule of fish oil + 1 tablet of vit. E + 1 tablet of calcium per day?

Angel

10

Chemistry / What is saltpeter?

« on: 27/01/2004 12:33:58 »

I came across a piece of information that says gunpowder are made of charcoal, sulphur and salpeter. What is salpeter anyway?

Angel

"The people who will succeed are those who see the invisible and do the impossible."

11

Chemistry / Heavy Gases

« on: 23/01/2004 11:06:05 »

Gases usually have small molecule mass, like H2, O2, CO2.
For a compound like SF6 which has a Mr of 108, you would expect it to be solid or liquid at room temperature but it's in fact a gas. How is this possible? Something to do with the interaction between molecles?

Angel

"The people who will succeed are those who see the invisible and do the impossible."

12

Complementary Medicine / Chinese Herbal Medicine

« on: 20/01/2004 09:25:25 »

What does everybody think about Chinese herbal medicine? Anyone tried it before?

Western medicine tend to be antibiotics, painkillers...etc. I tried hebal medicine few times, they seem to tackle the problem in another way. For example if your liver is weak they give you something to make you liver function better and the medical problems related to a bad liver will just disappear gradually. This is just how I think they work but it could be completely rubbish. Honestly, I have no ideal how herbal medicine work.

Angel

"The people who will succeed are those who see the invisible and do the impossible."

13

Complementary Medicine / Potato peel prevent bacterial infection

« on: 05/12/2003 12:36:24 »

People use to put potato peels over the wound to prevent bacterial infection. Apparently, this old remedy does work.

Potato peel contain a substance that block the binding site on bacteria preventing it binging to body cells and therefore cannot manifest itself over the wound causing an infection.

So instead of using an antibiotic to kill the bacteria and worry that it might eventually become resistant to the drug, blocking the binding site on bacteria with a similar shaped molecule would also work. It is an approach which I think will go a long way.

Angel

"Anyone who has never made a mistake has never tried anything new." -Albert Einstein

14

Physiology & Medicine / Thyroxin Disorder

« on: 03/09/2003 19:31:31 »

Recently got the news that my aunt has thyroxin disorder[]. Her thyroid gland produces too much thyroxin that the metabolic rate of the body becomes too high. She's lost a lot of weight....poor thing. Fortunately, she discovered this condition early and now her doctor puts her on medicine treatment for a year. What could be the cause of this kind of disorder?

Angel

15

Complementary Medicine / soya and osteoporosis

« on: 17/05/2003 08:32:33 »

Anybody seen the article about soya and infants in this week's New Scientist?

It said that babies that are fed with soya-based formula are more likely to have discomfort during menstruation. And baby boys born from vegetarian mothers were 5 times as likely to have genital abnormalities. All these is due to higher levels of phytoestrogens in the body. Does anybody know why?

The article also mentioned that phytoestrogens have been claimed as remedies for osteoporosis.

Osteoporosis is caused by the break down of pyrophosphates, which our bones are made of, by an acid (HCl) secreted by 'jellyfish-like cells' present in the fluid surrounding the bones. This disease is currently treated by replacing lost pyrophosphates with biophosphates, which have similar chemical structures and are acid stable. A powerful drug also cause the 'jellyfish-like cells' to self-destruct.

Back to the question, how does phytoestrogens help to reduce osteoporosis? Any expert in this field?

Angel

16

Physics, Astronomy & Cosmology / What happens if you drill a hole through Earth ?

« on: 05/07/2003 19:47:21 »

Right, this is an interesting one.

Say if you drill a hole through the centre of the earth and drop a ball into the hole, what will happen to the ball?

I think some of you guys have heard this one before. And Tom, you can't answer because you know the answer already.

Angel

17

Physiology & Medicine / Laser Eye Treatment

« on: 09/06/2003 21:55:22 »

My mum is thinking about doing a laser eye treatment but is concerned about the safety of the procedure and the effectiveness of the treatment. I have the following questions:-

 

• How does the treatment actually work?
• what is success rate of this treatment at the moment and how safe is the operation?
• Does anybody know people who have done laser eye treatment and what did they think about it?

Angel

18

The Environment / What are the rules regarding the use of biodiesel?

« on: 04/06/2003 16:42:16 »

I saw an article on a science magazine about 'biodiesel'. Basically, it's to do with using sunflower oil in engine rather than diesel. I think a lot of people probably have heard this before.[]

Apparently, engines can be modified to run on sunflower oil. Isn't it a great news? Don't know about Australia or Canada but the petrol in UK is really expensive (at least I think so). Also sunflower oil has low CO2 emmission and no harmful combustion products. Even better, it's renewable![^]

The ridiculously, a man was caught and fined for using sunflower oil to run his car![:0]

Angel

19

Chemistry / Crystal Formation

« on: 28/05/2003 16:09:14 »

Why does crystal grow bigger when you allow a hot liquid to cool slowly? For example, basalt has small crystals because it's formed by rapid cooling of molten rock whereas granite has large crystals. Is it because the molecules have more time to move into position abd bond with neighbouring molecules to form a regular lattice structure?

Exodus, I think you should be able to answer this question. So help!

Angel

20

Chemistry / How do indicators work in chemistry?

« on: 23/05/2003 08:00:48 »

How do indicators work?

For example, why is the universal indicator able to change into different colours according to the acidity of the substance? I'm guessing that this is to do with the redox of the chemical in the universal indicator, probably one of the transition metals because they are the only ones which can have varied oxidation states and produce different colours.

Angel