Cumulative General Science/Technology Quiz

[Mise]

But the question asked at STP. Is hydrogen solid then?

The least dense gas at s.t.p. is what I meant.

 

[Perfection]

Yup!

It's even been hypothesised that metallic hydrogen can be formed, with a separation between atoms less than the Bohr radius.

I don't know whether neutron stars or black holes are more dense than solid hydrogen, but the point of the question was that Hydrogen forms the least dense gas and the most dense solid (of all the elements <-- maybe I should've specified that!).

Stickciv / dutchfire 's up, depending on who asks first I guess.

I'm very skeptical of this mise.

It seems to me that while yes, hydrogen can be compressed into a solid that is denser then the solids observed at around STP, I see no reason why other elements can't be compressed further too (and I know for a fact they can be)! In fact, it seems to me that elements in the middle of the perioidic table like iron can probably be compressed into much denser solids, because unlike hydrogen they don't undergo energetically favorable fusion reactions under huge pressure.

 

[Genocidicbunny]

Perfection is right. I put the Solid Hydrogen in as a joke..never expecting it to be the actual answer. The only reason Hydrogen would form a dense solid is because its a single proton, meaning that Hydrogen can theoretically be compressed down to a very high density. Its not very feseable though, especially considering that one would have to overcome what is basically an almost perfect proton-proton repulsion.

 

[Perfection]

Well, we should keep going (though Mise should comment), I think Stick deserves a whack at asking the next question.

 

[Genocidicbunny]

Naw, dutchfire can have it. Im better at answering than thinking up of questions.

 

[dutchfire]

Describe how a critical nuclear reactor can be brought to a higher power.

 

[ainwood]

What is the least dense gas in existence? (at s.t.p.)

Not that it actually affects the answer, but standard temperature & pressure is very ambiguous: It is a different set of conditions depending on industry, country etc.

http://en.wikipedia.org/wiki/Standard_temperature_and_pressure#Definitions_in_current_use

 

[Mise]

I'm very skeptical of this mise.

It seems to me that while yes, hydrogen can be compressed into a solid that is denser then the solids observed at around STP, I see no reason why other elements can't be compressed further too (and I know for a fact they can be)! In fact, it seems to me that elements in the middle of the perioidic table like iron can probably be compressed into much denser solids, because unlike hydrogen they don't undergo energetically favorable fusion reactions under huge pressure.

1. There's two things here, solid Hydrogen, which is just Hydrogen that's frozen (NOT AT STP, obviously...).

2. Metallic Hydrogen, which is an allotrope of Hydrogen that is stable at STP, and whose nuclear separation is less than the Bohr radius (on the same scale as the DeBroglie wavelength of an electron).

Solid Hydrogen is denser than the solid form of any other element, which is what I was getting at...

It's just one of those random facts that I picked up along the way. Thought it would make an interesting question!

 

[Perfection]

I'm skeptical that frozen hydrogen is that dense, where did you get that from?

 

[dutchfire]

Describe how a critical nuclear reactor can be brought to a higher power.

Anyone want to answer that question?

 

[brennan]

Remove the moderators.

 

[Perfection]

I agree.

 

[dutchfire]

Remove the moderators.

No, not quite. You have to remove something though.

 

[Brighteye]

Add more uranium.

 

[Perfection]

The Coolant?

 

[brennan]

I agree.

I can't believe I said that with you around.

 

[GoodGame]

Move the reaction rods closer together, add a bit more water and a a turbine with longer fan arms?

(rAdio70qical NoOb).

 

[Mise]

Throw petrol on it?

 

[peter grimes]

From what I understand about nuclear reactors, there are two things mediating the reaction: Fuel (usually Uranium), and Neutrons. So adding either, or removing the absorbtive medium (usually graphite) will increase the rate of the chain reaction.

But I honestly have no idea

 

[dutchfire]

From what I understand about nuclear reactors, there are two things mediating the reaction: Fuel (usually Uranium), and Neutrons. So adding either, or removing the absorbtive medium (usually graphite) will increase the rate of the chain reaction.

But I honestly have no idea

I suppose you could add more Fuel, but you don't really want to have to go into a working nuclear reactor every time you want to change it's power


A nuclear reactor is a chain reaction. 1 Neutron hits a Uranium (usually) core, splitting it into two smaller cores, and releasing several (3/4) new neutrons. These neutrons can then hit new uranium cores.

The problem with this is that if all new neutrons would set about a new reaction, the number of reactions (= power) would increase exponentially. This would quite quickly result in too much power to handle, and then entire thing would explode/meltdown/become too hot.

Therefor, there are control rods to catch a certain percentage of the free neutrons, so that from the neutrons created in a single reaction, only 1 will start a new reaction. This is called "the k-factor is 1". That means the power is constant.

To increase it, you temporarily remove the control rods (you lift them up a bit), the k-factor becomes larger than 1, the power starts increasing, and once you reach the desired level, you lower the control rods again, the k-factor will be 1 again, and the power will be constant (but higher).