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chemgoddess 19.10.2007 10:56

Ask a Scientist
 
Okay, I'm gonna try this out. Any burning science questions that people would like answered, hopefully me and the other scientists on the forum can answer.

But remember, I'm a chemist, I'm not omniscient. I'll do my best.:msnnerd:

misterazz 19.10.2007 10:58

Re: Ask a Scientist
 
Hi-
I can help in the field of molecular biology

Kittster 19.10.2007 11:03

Re: Ask a Scientist
 
Great idea for a thread!
Since Psychology gets classed as a science - ask away! ;)

But I have one for Chemgoddess:
When you mix Maizena with a certain quantity of water, it has this weird quality of feeling hard and liquid at the same time (try it, you'll be playing for hours, great for kids). Now I'm not sure how to Google this so my question is - how does that work?

Dodger 19.10.2007 11:17

Re: Ask a Scientist
 
This one is a job for the chemical engineer... sorry chemgodess, you can have the next one ;)

A cornstarch solution is a type of non-Newtonian fluid, a fluid whose viscosity changes with shear.

In the case of a mixture of cornstarch and water, the viscosity increases with the shear rate - so it gets harder the more you stir. This is known as a dilatant material.

The opposite (viscosity decreases with shear) is a pseudoplastic material. A common example of this is tomato sauce - we all know how hard is getting that stuff out of a bottle, but once it starts moving, you can't stop it.

Uncle Max 19.10.2007 11:28

Re: Ask a Scientist
 
If the Universe is expanding, where or what is it expanding into?

I've seen an episode of Heroes and want to develop my ESP. Any tips?

One more: why doesn't the Earth's gravitational force provide / allow a constant law regarding hydrodynamics? :confused: It's complicated and I need an idiots guide. Thanks for any feedback.

nqnln 19.10.2007 11:33

Re: Ask a Scientist
 
Quote:

Originally Posted by Dodger (Post 118437)
This one is a job for the chemical engineer... sorry chemgodess, you can have the next one ;)

A cornstarch solution is a type of non-Newtonian fluid, a fluid whose viscosity changes with shear.

In the case of a mixture of cornstarch and water, the viscosity increases with the shear rate - so it gets harder the more you stir. This is known as a dilatant material.

The opposite (viscosity decreases with shear) is a pseudoplastic material. A common example of this is tomato sauce - we all know how hard is getting that stuff out of a bottle, but once it starts moving, you can't stop it.

The word which describes these processes is nice. Try to fit it into daily conversation: thixotropy or thixotropic

Bartholemew 19.10.2007 11:33

Re: Ask a Scientist
 
I have one: You're boiling water to cook pasta. When the water gets hot enough to add oil and salt, why does the water start boiling like crazy right when you add the salt?


(someone said there are no dumb questions)

Kittster 19.10.2007 11:34

Re: Ask a Scientist
 
Quote:

Originally Posted by Dodger (Post 118437)
This one is a job for the chemical engineer... sorry chemgodess, you can have the next one ;)

A cornstarch solution is a type of non-Newtonian fluid, a fluid whose viscosity changes with shear.

In the case of a mixture of cornstarch and water, the viscosity increases with the shear rate - so it gets harder the more you stir. This is known as a dilatant material.

The opposite (viscosity decreases with shear) is a pseudoplastic material. A common example of this is tomato sauce - we all know how hard is getting that stuff out of a bottle, but once it starts moving, you can't stop it.

Woooow *think wow like those little green alien toys did in Toy Story II*, I feel like my IQ has just gone up five points.

As for the universe, that's a tough one, as there is actually nothing outside of the universe. I find this totally unfathomable and explain this shortcoming with the fact, that my brain has boundaries given by the skull it lives in.

But if you want a really good explanation for that, I recommend Bill Bryson's Short History of Nearly Everything, also available as an audiobook and a brilliant read for people who like simple explanations for complex things.

readingsteve 19.10.2007 11:34

Re: Ask a Scientist
 
Brilliant idea for a thread. Will have to ask some of my nuclear physics friends if they have any decent questions to ask!!:msnnerd:

Kittster 19.10.2007 11:38

Re: Ask a Scientist
 
Apparently, for physicists, physics is the only science, everything else is just stamp collecting. :p

Uncle Max 19.10.2007 11:44

Re: Ask a Scientist
 
Thanks Kittster. I understood there's no evidence suggesting there's anything beyond the Universe, but you seem to have insider knowledge :p

And before the Physicists get all heady, remember Philosophy is the Mother of all Science :cool:




Who am I?
Why am I here?
What's it all about..?

Uncle Max 19.10.2007 11:54

Re: Ask a Scientist
 
Quote:

Originally Posted by Bartholemew (Post 118456)
I have one: You're boiling water to cook pasta. When the water gets hot enough to add oil and salt, why does the water start boiling like crazy right when you add the salt?


(someone said there are no dumb questions)

Salt causes the water to boil quicker, that's why. Add it before it boils, and save a few Rappen / Cents from your electricity bill. Remember to stir, though, as salt also corrodes.

Don't bother adding oil, it's useless. Use more water instead - hence deep pasta pans :cool:

chemgoddess 19.10.2007 11:59

Re: Ask a Scientist
 
That's not a dumb question at all, actually a quite interesting one and not trivial at all.

So when we think about what happens when water boils. You have liquid water getting heated up enough that it has enough energy to go from the liquid to the gas phase, a phase transition. Nucleation is the term for a phase transition that occurs in small region. The spots on your pot where see the tiny bubbles at the bottom of soon to be boiling water, could be considered nucleation sites, you have some water molecules trying to go from liquid to gas. Nucleation is a pretty difficult, not fully understood concept but it tends to happen on surfaces. Generally your pot is pretty smooth so there aren't a bunch of nucleation sites but eventually your liquid to gas bubbles grow bigger, and your gaseous water gets enough energy to break free.

But as I said previously nucleation sites occurs on surfaces, when you add salt you add a whole bunch of little tiny places where your water can undergo it's phase transition and hence it all starts going to the gas phase, i.e., boiling all at once.

It's kinda the same phenomena as the mento's/diet coke explosion. When you put in the rough surfaced mento, all the CO2 dissolved in the soda has a ton of new nucleation sites and hence can fly outta the bottle, i.e., outgas.

Hope that makes sense.

Quote:

Originally Posted by Bartholemew (Post 118456)
I have one: You're boiling water to cook pasta. When the water gets hot enough to add oil and salt, why does the water start boiling like crazy right when you add the salt?


(someone said there are no dumb questions)


chemgoddess 19.10.2007 12:00

Re: Ask a Scientist
 
Actually, if you add the salt before, it raises the boiling point of water, so it would take longer to boil. Please see above post for explaination.

Quote:

Originally Posted by Uncle Max (Post 118480)
Salt causes the water to boil quicker, that's why. Add it before it boils, and save a few Rappen / Cents from your electricity bill. Remember to stir, though, as salt also corrodes.

Don't bother adding oil, it's useless. Use more water instead - hence deep pasta pans :cool:


bozothedeathmachine 19.10.2007 12:08

Re: Ask a Scientist
 
Quote:

Originally Posted by chemgoddess (Post 118486)
Actually, if you add the salt before, it raises the boiling point of water, so it would take longer to boil. Please see above post for explaination.

That's true, but from what I understand in order for salt to affect the boiling point of water in a pot in any noticeable way, one would have to add so much salt to the water that it would make anything boiled in it unpalatable.

Of course, I'm no chemist.

chemgoddess 19.10.2007 12:10

Re: Ask a Scientist
 
Yes, in a noticable way. But that still doesn't detract from the fact that salt raises the boiling point of water as a rule. And of course you'd have to consider how much and what type of trace minerals are in your water, etc. etc.

Quote:

Originally Posted by bozothedeathmachine (Post 118490)
That's true, but from what I understand in order for salt to affect the boiling point of water in a pot in any noticeable way, one would have to add so much salt to the water that it would make anything boiled in it unpalatable.

Of course, I'm no chemist.


Bartholemew 19.10.2007 12:17

Re: Ask a Scientist
 
I love this thread - great idea of the scientists' part!

Does anybody watch Die Sending mit der Maus on German TV Sundays? They do cool explanations for things too, although there's no particular focus on science there.

bozothedeathmachine 19.10.2007 12:19

Re: Ask a Scientist
 
Quote:

Originally Posted by Uncle Max (Post 118450)
If the Universe is expanding, where or what is it expanding into?

Technically, the answer is "nothing". I guess it depends on which theory du jour you subscribe. Hyperspace theory claims that the instant before the big bang, a 10-dimension space decayed into 2 "pieces", of which:
1) one piece expanded into an infinite 4-dimension macro space in which our universe is expanding
2) the other piece contracted/collapsed into an infinitesimal 6-dimension space about the size of the Planck length.

Dodger 19.10.2007 12:35

Re: Ask a Scientist
 
Quote:

Originally Posted by Bartholemew (Post 118497)
I love this thread - great idea of the scientists' part!

Does anybody watch Die Sending mit der Maus on German TV Sundays? They do cool explanations for things too, although there's no particular focus on science there.

That is a fantastic show (from your avatars, you are clearly also a fan). No matter how old you are, there is something to learn here. The way that they are able to explain complicated things in a way that even pre-schoolers can understand it is commendable. Reminds me of the good ol' Curiosity Show we had in Australia when I was little.

bubbles4352 19.10.2007 12:49

Re: Ask a Scientist
 
Here's a social psychology question: how do people instinctively know when they are being looked at? Or is it a myth?


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