vrus

Oxygen need something to burn with. If you have a gas jar filled with oxygen, it will require something to burn with to use up the oxygen in the same.

Also' date=' when in its liquid form it seems to defy a lot of the laws of physics, it climbs up the side of beakers and stuff - its really wierd!

 

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One of my book says that there exists a 'super-fluid allotrope' of Helium, the can climb out of its cantainer !

A super-fluid is a fluid that has or creates no friction right ?

This whole thermite thing gives me the feeling of someone trying to push something with high inertia but once that thing starts moving its unstoppable !

Also, it can be done with other reactants right ? My teacher told me the larger the difference in reactivity the more violent it is. Has anyone done it using different reactants ? What was it like ?

Did you know that, when lightning occurs as we see it, it is actually the scond part of the lightning process ? So actually, an 'invisible' charge goes up from the ground upto the clouds and then we see the flash that strikes the exact same place the the charge went up from. So maybe, if we can actually cause/ control the place it goes up from, we could control where the lightning hits. An insulated conductor with a high static charge artificially created by direct contact/ induction...

keep thinking....

Sounds like....

 

Dosen't Carbon Monoxide form a strong bond with Haemoglobin' date='forming Carboxyhaemoglobin, thus rendering the molecule usless? I would consider that a cumulative effect given enough of it inhaled... Although the blood cells would quiteprobptly be destoyed as a result...

 

Cheers,

 

Ryan Jones[/quote']

 

But caboxyhaemoglobin can be removed from the blood by breathing pure oxygen right ? My source was an IGCSE book I think ..... : )

Can someone help me out and give me a good explanation about Pyroelectric crystals and Piezoelectric crystals ? Help appreciated ! THnks.

Similar to what douglas said, I found out from one of my old books, that in these kind of situations, the two objects are connected by a copper wire first.

So basically planes never get charged ? Well, well, well...! Is there any website that explains more about this ? Thnks. for the help !

Man ! after reading this thread, I ain't going anywhere close to this stuff! No way. Not for me !

the spark lasts maybe all of a millisecond so both planes will be equally charged(if there happens to be one for some absurd reason) by the time the fuel starts flowing so it won't be lethal in any way.

 

planes are earthey on the ground because they make fantastic targets for lightning. it is also to prevent possible faulty wiring from electrocuting people and making sparks. on the ground it is earthed for exactly the same reason your toaster is' date=' to prevent YOU getting a shock for faulty wiring. the thing about clods charging planes up is mostly myth. while it is possible for a plane to get a slight electrical charge it is dissipated to colliding air quite rapidly[/quote']

 

I am no expert in static electricity . But I know that planes are insulated conductors. Their bodies are metal alloys (conductor) but when on earth, they are insulated by their rubber tires. So they would keep the charge without earthing it.

 

But surely, planes get charged while flying ?

Planes get charged up when flying through clouds right? That's why they're earthed when they land. But in the case of mid-air refuelling, the planes can't be earthed. If there is a spark, then things can be lethal. How do they prevent this from happening ?

Do they make the refuelling probe out of rubber or an insulator ?

What countries are involved in the F-35 project ? I know USA and Britain are. Any others ?

Two points ppl.

First, the F-35 DOES NOT have thrust vectoring. Only the Raptor does.

Second, this thread is supposed to be about a RUSSIAN 5th gen. fighter! For the JSF, etc start a new thread. In fact I'll do it myself and we can argue about thrust vectoring ther !

Entropy is a measure of disorder. It's kind of an abstract value and I'm not fully sure how it's directly measured' date=' but basically speaking the more entropy a system has, the less ordered the molecules/atoms are. Solids have low entropy because the atoms are aligned in a set pattern, while gases have a lot of entropy because they can go in any which way.

 

Being spontaneous means the reaction will proceed on its own without any need to input energy. If you mix hydrogen gas and oxygen gas, it will slowly happen, but the two will react and form water. (If you add a catalyst or a little bit of heat, then it proceeds quite rapidly). As a result, the Delta G for the reaction of hydrogen and oxygen is pretty negative. On the other hand, if you have hydrogen fluoride dissociating into hydrogen and fluorine gas, the Delta G for that reaction is VERY positive. That means that no matter how long you wait, you will NEVER see the HF dissociate into H and F. The only way it will happen is if you put energy into the system.

 

Here's another analogy. Let's say that you have a block of ice outside on a warm day as well as a beaker of water. The 'reaction' of the ice melting into water is a spontaneous occurance. It might take a while, but if you wait long enough all the ice will melt. The delta G of the reaction H2O(s) => H2O(l) at 300K is negative. The solid will spontaneously form the liquid. On the other hand, the reaction of H2O(l) => H2O(s) is NOT spontaneous. You can wait all you want, but the water will not solidify at 300K. The delta G for the 'reaction' is positive. You have to put energy into the system in order to get the water to solidify.[/quote']

 

 

That's a great explanation! Thanks again!

A negative value indicates a spontaneous reaction. A positive value indicates a non-spontaneous reaction.

Thanks. That really clears things up. However, how would you define spontaneous ? I've never really used that word before. I think I know, but its better if you clear it up.

Another thing; doesn't entropy have many different meanings ? Someone told me it it is a calculation of all the possible ways a reaction can go ?

What do you say about this ?

Hello' date='

 

You know how you go to the refrigerator and take out the bottle of ketchup and it is cold and sealed tightly? So you think a little warm water would ease it. When you turn on the tap and stick the bottle neck onto the warm water, the bottle neck cracks!

[/quote']

 

I think it is called unequal expansion of solids. Honestly, I don't know how it happens, but I think it could be because there is such a large temperature change and since the glass is a bad conductor of heat, in the warmed region, molecules are gaining lots of KE much faster than the others causing a large fluctuation in energy levels. Can someone confirm this pls. ?

enthalpy entropy and gibbs free energy are all related by

i use d instead of delta here(need to learn latex)

 

dG=dH-TdS

 

where

dG = change in gibbs free energy(J)

dH = change in enthalpy(J)

T = temperature(kelvin)

dS = change in entropy(J)

Yeah I heard about that formula, but what do they actually mean ?

What are entropy & enthalpy ? Are they related ? If so, how ? And what is 'Gibb's free energy' ? Thnks.

I'm curious on whether esters are dangerous if consumed directly ?

So these ions are'nt dangerous to us ? I mean what about alpha radiation, it is basically a Helium ion and if it penetrates, its trouble ! Thats the example i couldn't understand.

this is one thing i hate

the F-22 does have stealth cababilities but that doesnt mean that its not invisible to radar' date=' it only means that the signiture is decreased and on the less sophisticated radar nothing comes up at all

stealth planes are only invisible to radar to some extent[/quote']

 

You're right!

And its getting easier to do it. Obviously its not that easy, but applying radar-absorbent paint causes some effect of some extent!

Can you give me an example of them existing on their own ?

I thought the Su-47 project was cancelled as they found problems at high speeds due to the froward swept wings?

And I also read that the MiG-1.42 was not going to be used, but used as a Tech. Demonstrator ?

Can ions exist on their own ? ( In terms of stripping off or adding electrons to elements ) Will they combine with things in the air ?

get dilute salt slution' date=' dip in 2 iron electrodes, hook them up to dc current. mine was 30 volts adapter. id run that for a few hours, the bucket would be full of stuff floating around. id poaur the stuff in a cup, then let it settle, then pour off the execc, and repeat. after a while i had like a cup of the gunk still in water. id set that under a lamp for a day or two, and id get a good amount. after u dry it its like brow, but after u heat it in a dish its nice and red.

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I did somenthing similar, but not the same. I had a 30 V DC adaptor too. I striped the copper wire of insulation and put it in an electrolyte of plain tap water. The other electrode was an old iron nail connected witha croc. clip. I kept on getting loads of reddish/brownish stuff. After the whole vessel was like dark brownish, I emptied it and filled it up with clean water again to continue, since I have no use for whatever the substance was. It smelt like Iron though. I am presuming it is Fe2O3.

 

On another occasion, I kept on elctrolysing sea water! with different electrodes( the last and longest used was the iron nail) until the solution was of a similar colour to that mentioned before. I removed as much excess liquid and left the vessel to evaporate. Two days later, I was left with a crust of solid with liquid beneath it. On turning, atirring and leaving for another day, I formed a fine red/brown powder, again smelling of Iron. What could this be?

I don't understand why on earth you want Rust ? What's the use ? (none that I know). It doesn't smell great either !