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  #881  
Old 23.12.2009, 14:26
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Re: Ask a Scientist

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OK. I have an "Englishman-abroad" themed question....

As many EFs will agree, a cup of tea has to be made with boiling, or near boiling water - it just doesn't taste the same with "hot water", one of the reasons, I think, that cups of tea bought or served in hotels, restaurants and coffee shops in Europe (quite generally) taste different.

1) What is the critical temperature needed to release the flavours we tea-lovers associate with our tea?
...
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1) Temperature is not the critical factor, rather time. If the water is too cold, of course you'll get nothing, but the infusion time is a greater driving force than the water temperature.
So what you're saying is that temperature is and is not the critical factor.

As any high-altitude climbers here would confirm; to make decent black tea, temperature
is the critical factor which can be partly compensated for by additional brewing-time.
.
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  #882  
Old 27.12.2009, 23:58
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Re: Ask a Scientist

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Why does red wine become thinner with age and white wine becomes more viscous?
But is it true? Read a nice quote today:
"In God we trust. All others bring data."

You need a lot of small molecules to make water noticably more viscous. Small amounts of polymer (long molecules) would be much more efficient.
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  #883  
Old 28.12.2009, 03:13
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Re: Ask a Scientist

Why does water expand when it freezes? Also, why is water incompressible?

Edward J. Cunningham
Derwood, MD
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  #884  
Old 30.12.2009, 11:51
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Re: Ask a Scientist

Second things first...

For "most practical purposes", water can be regarded as
incompressible; the underlying reality however is that water
has low (but not no) compressibility.


When normal ice forms, at temperatures round 0C and pressures
round 1 atmosphere, the crystalline structure that the molecules
adopt is wider-spaced than that of the liquid form, hence a given
mass of water will "expand" when changing phase to solid.

IIRC... there are 13 or 14 different "types" of ice; the type depends
on the temperature/pressure combo under which it forms, and most
are denser than water.
.
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  #885  
Old 30.12.2009, 13:44
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Re: Ask a Scientist

Not to step on anyone's toes, but the answer seemed a bit over simplified, and lost the rational behind the observation; though the end answer is the same.

For ice vs. water density,

The molecular structure of water being H2O, the H repels H, being electropositive, and the O repels O, being electronegative. this creates a molecule that appears somewhat like a ^ with O at the point, and H on the ends.
Note that an H of one molecule is still attracted to the O of another. They bond in a "Hydrogen bond", an electrostatic bond that is weaker than both an ionic, and covalent bond.

This structure interacts with the other molecules in its environment, and as liquid state, moves quite a bit in an out of the polarity equilibrium, filling the space as Hydrogen bonds are formed and broken.
As ice, the molecules move considerably less, and are generally "frozen" into an equilibrium state. This creates small spaces as the molecules are asymmetrical, and therefore takes up more space overall.

Here's a pic of the structure that I found: http://www.benbest.com/cryonics/icecryst.gif Note: the posts are hydrogen bonds.

Oh, and there are 15 types of ice, of which hexagonal is the only "naturally" occurring.
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  #886  
Old 02.01.2010, 18:08
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Re: Ask a Scientist

I was peering at a diamond today, as one does, and it suddenly occurred to me how strange it should be that one can see right through a solid piece of stone.

Could somebody, therefore, explain transparency to me?

Please use simple words and concepts, because I'm not very clever. Thank you.

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  #887  
Old 02.01.2010, 18:48
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Re: Ask a Scientist

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I was peering at a diamond today, as one does, and it suddenly occurred to me how strange it should be that one can see right through a solid piece of stone.

Could somebody, therefore, explain transparency to me?

Please use simple words and concepts, because I'm not very clever. Thank you.

My guess is that big gaps between the teeny weeny things that make up the substance allows the light through. By big, I mean big compared to the size of the teeny weeny bits.
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  #888  
Old 02.01.2010, 21:14
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Re: Ask a Scientist

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My guess is that big gaps between the teeny weeny things that make up the substance allows the light through. By big, I mean big compared to the size of the teeny weeny bits.
One of my physics teachers, when we first began discussing X-ray diffraction, said something like "and never say 'the light goes through the gaps in the atoms'".

Quick answer.
The particular allotrope of carbon, known as diamond, is transparent because it does not have (m)any electrons in energy states that correspond to the energies of photons in the visible spectrum.

Longer answer.
The colour of something is due to the wavelengths or frequencies said substance does not absorb; or absorbs and then emits without changing the wavelength, or frequency, of said photon. In a sense, the colour of something is precisely not its colour.

Because photons are the quanta of the electromagnetic interaction, all this absorption, emission and so on is due to the electromagnetic interaction of photons with matter. At frequencies below hard X ray frequencies all this happens as a consequence of electrons interacting with photons.

So now we only need to consider two agents in understanding why something has a particular colour: photons and electrons.

For any wave, and a photon behaves like a wave under the right circumstances, there is a simple relation between the wave's speed, frequency and wavelength.

There is another ingredient though. This ingredient is energy.

The energy of a photon is constant, and is proportional to its frequency.

The energy of an electron is more complicated. However one idea always applies, which is that an electron can only change its energy state by the emission or absorption of a photon. But an electron in a diamond does not have an unlimited choice of energy states accessible via emission or absorption. It is constrained by its local environment.

Should there be no energy states available to an electron in a material (for example diamond), that correspond to the energies of photons in the visible spectrum, then the electrons in a diamond cannot "see" these photons, and the substance appears to be transparent.
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  #889  
Old 02.01.2010, 21:25
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Re: Ask a Scientist

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So what you're saying is that temperature is and is not the critical factor.

As any high-altitude climbers here would confirm; to make decent black tea, temperature
is the critical factor which can be partly compensated for by additional brewing-time.
The question related to the serving of tea in a generic European restaurant, not at the top of a mountain.

As I said in my answer, if you are below a certain temperature, of course you will get nothing at all. But the question was this: why does tea taste different here in Europe compared to in the UK? In both cases, the temperature of the water is the same, but the infusion time is different, leading to the differences in flavour as previously described. So, to answer the original question, time is more important than temperature.

At higher altitudes, water boils at a lower temperature due to the reduced atmospheric pressure. Therefore you can boil water and still have the water at a less-than-desirable temperature for the preparation of tea. So if you can't reach a good temperature, of course the tea will be terrible, no matter how long the infusion time may be. So, in this respect, you are right. But, as I said, this situation is different to that given in the original question: at lower altitudes, reaching the right temperature (drinkable or undrinkable tea) is far simpler than getting the right time (getting the flavour to match your personal preferences).
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  #890  
Old 02.01.2010, 21:31
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Re: Ask a Scientist

The water itself is also a major factor.
Rain water, town supply with added chemicals, well water, melted snow water, all completely different and make a completely different tasting cup of tea, irregardless of the boiling temperature.
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  #891  
Old 02.01.2010, 22:15
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Re: Ask a Scientist

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Quick answer.... Longer answer
Nice one, thank you!

I'd be lying if I said I understood it all, but the responsibility for the lack of comprehension lies with me.

I'll read it properly when I haven't got a quarter of a bottle of brandy inside me.
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  #892  
Old 02.01.2010, 22:27
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Re: Ask a Scientist

I have a question. If we look into outer space, we possibly see a star that is presently non-existent anymore but because the light still reaches us, we still perceive a star. If we would hypothetically speaking, travel into outer space towards a star that actually still exists...and we would look back at earth...where would the threshold lay of actual existence and mere light reaching us?
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  #893  
Old 02.01.2010, 22:29
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Re: Ask a Scientist

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If we would hypothetically speaking, travel into outer space towards a star that actually still exists...and we would look back at earth...where would the threshold lay of actual existence and mere light reaching us?
The moment you left earth.

In fact, the moment you looked down at the ground, even before you'd taken off.
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  #894  
Old 04.01.2010, 15:39
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Re: Ask a Scientist

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The water itself is also a major factor.
Rain water, town supply with added chemicals, well water, melted snow water, all completely different and make a completely different tasting cup of tea, irregardless of the boiling temperature.
Yes, a very good point. I forgot that. Thanks for bringing that up.
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  #895  
Old 04.01.2010, 16:23
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Re: Ask a Scientist

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At higher altitudes, water boils at a lower temperature due to the reduced atmospheric pressure. Therefore you can boil water and still have the water at a less-than-desirable temperature for the preparation of tea. So if you can't reach a good temperature, of course the tea will be terrible, no matter how long the infusion time may be.
A snippet I recall from junior school was the inability to make decent tea faced by early Everest climbers, due to the altitude and lower boiling point of water.

According to our teacher later expeditions used some kind of pressurised kettle to get around the problem, but I've never heard of such a piece of kit since. I didn't drink tea myself at that tender age, and couldn't see what the fuss was about

So my question is:-

Are there such things as pressurised kettles for high altitude mountain climbers, with the sole purpose of making a decent cuppa?

(I would have thought that in order for one to be safe it would need to be quite heavy and therefore to be avoided.)

Last edited by JVC; 04.01.2010 at 16:57.
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  #896  
Old 04.01.2010, 16:35
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Re: Ask a Scientist

Im sure you can. A quick google search brought up this (not an actual kettle as such but you get the idea)

http://www.thefind.com/sports/info-m...t-titan-kettle

Ive seen some sort of kettle around before, but there are tonnes of high altitude products out there.
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  #897  
Old 09.01.2010, 10:54
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Total acids and pH

Would a solution containing 10g/l of tartaric acid with a ph of 3 taste more acidic than a solution of 20 g/l of tartaric acid with a ph of 3.2

How does ph relate to the measurement of acidity found?
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  #898  
Old 12.01.2010, 14:49
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Everything you wanted to know about String Theory...

...answered in 60 seconds.

And folk once accused The Times of dumbing down!!!
.
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  #899  
Old 12.01.2010, 14:55
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Re: Ask a Scientist

How do you measure laziness?
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  #900  
Old 12.01.2010, 15:39
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Re: Total acids and pH

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Would a solution containing 10g/l of tartaric acid with a ph of 3 taste more acidic than a solution of 20 g/l of tartaric acid with a ph of 3.2

How does ph relate to the measurement of acidity found?
IIRC, "sourness" varies independently with pH, concentration, and specific
anions(s) involved.

So, I have a sneaking suspicion that only empirical data would answer this
question satisfactorily.

Is there a wine question lurking behind this one?
.
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