RELATIVITY QUESTIONS! (and other common queries)

[The-Rabid-Monkey]

I think I may have found an argument for intelligent design: thermite was "intelligently designed" so it's hard to make, to avoid idiots melting their faces off

Not saying you are one, good luck with that. Al is closer to Lithium than Cu in here (I never remember how to use the reduction potentials) so Cu will not be oxidized by it.

It's not hard to make, it's hard to obtain the Al powder, for specific reasons.
And I wasn't wanting to oxidise the copper, I was wanting to transfer the Sulphate from the Al to the Cu, but after talking to my chem teacher, he reckons that won't work.
And I had a look at that data and I don't overly understand it, but would I be correct in saying magnesium is more reactive than aluminium? Meaning that this might work:
Al + 3HCl ==> 3H + AlCl₃
2AlCl₃ + 3Mg ==> 2Al + 3MgCl₂
Or is that just wrong? And besides, I don't know where to get concentrated HCl.

[AFedchuck]

If you didn't know that copper wouldn't reduce aluminium, I would recommend staying away from conc HCl and thermite, unless your practical skills are significantly better than your theoretical. Magnesium will reduce aluminium, just about, but if you have access to Mg, there doesn't seem to me to be much need to have Al (unless Al is particuarly good for thermit due to some physical properties).
Incidentally, you WERE trying to oxidise copper, as you were trying to react copper to produce Cu II, i.e. lose electrons, which is oxidation.

[The-Rabid-Monkey]

I was pretty sure from the start that copper wouldn't work in that reaction, but i wanted to check.
"The aluminium reduces the oxide of another metal, most commonly iron oxide, because aluminium is highly combustible. The products are aluminium oxide, free elemental iron, and a large amount of heat."
That's why you use Al not Mg
Stupid paint shops and their not selling Aluminium powder...

[jmorgan3]

Mg should actually work just as well. It is even more combustible than Al (not the best way to phrase that, btw). The only thing that Al has over Mg is a resistance to corrosion. That might affect the reaction, as MgO-covered Mg powder might not react quickly enough.

[thoughtfully]

No discussion of burning magnesium would be complete without this. There are a lot of these stories and videos out now, but this is the original, and probably the neatest. Alas, no video.

[The-Rabid-Monkey]

Ok different topic now. I've just decided to get aluminium from the metal work room at school.

Now, this afternoon, just for shits and giggles I decided to put some bleach in a jar, put some water in, and chuck in a couple of iron rods that are connected to an AC adapter. Almost instantly the positive rod started bleeding some orange precipitate everywhere and the negative one started fizzing.
I predicted the fizzing, but this precipitate isn't something I predicted. I've looked through google for something to do with this, but didn't see anything that made sense. So here is my question. What is this orange precipitate? And it's probably a good idea to make sure the gas coming off is Hydrogen. I'm sure it isn't Chloride, because I don't start gagging and dying when I inhale it.
2NaOCL + 2Fe + 2H₂O ==> 2NaOH + H₂ + 2FeOCl is all I can think of, although it's probably wrong.

EDIT: I have just stopped the reaction now. I have done some testing to confirm the liquid in the container is a base of some sort (aka I stuck my finger in and it went all soapy).
Also for added information. Liquid is transparent and smells funny, closest I can think of is bleached lemons perhaps?
Precipitate is Copper coloured.

[Blokey]

I have done some testing to confirm the liquid in the container is a base of some sort (aka I stuck my finger in and it went all soapy).

This reminds me of way back in a Physics lesson, where we were doing tests on current, resistance etc of bulbs. The teacher wanted us to work out how to work out the temperature of the bulb. Of course, the correct technique was to work out the temperature coefficient using room temperature as a rough anchoring point for the resistance.
My friend instead took the, er, 'hands-on' approach. Funnily enough, the teacher did not consider 'fuck! that fucking burns!' to be a quantifiable data point.

[Steppenwolf]

I'm sure it isn't Chloride, because I don't start gagging and dying when I inhale it.

Be seeing you...

http://darwinawards.com/darwin/darwin2008-06.html

[The-Rabid-Monkey]

I didn't jam my nose in the jar and snort it haha.
I merely waffed some my way with my hand.

[anouk]

if it smells like bleached lemons it probably have to be chlorine, wouldn't it? cause the bleach smell would have to come from the Cl as for the lemons... was it lemon scented bleach? lol or perhaps the bleach smell was just unreacted bleach, and its smell can hang around pretty well

but i just remembered, with the H₂0 you added (and the liklyhood of there being H₂0 in the bleach), shouldn't that react on the electrode before the i've forgottern exactly why, bah! everything has become a fuzz since i left school

you don't necessarily die as soon as you smell it either (other wise i wouldn't not be typing this post, lol) i got a pretty strong whiff of it at work, someone had poured some very strong (lab strength) bleach in the sink with hot water and didn't rinse the sink, and i managed to lean over it and get a very big noseful of it. the wikipedia page for 'bleach' has some specific numbers, i think a couple of lungfulls of 1000ppm is fatal. actually that page might be able to help you... lots of simple equations and the like.

the orange precipitate sounds like it would of been rust, iron oxide

lol

[TheQuestion]

I don't think this warrants its own thread but heres my question:

What is the scientific definition of measurement, specifically:

If I mass a potato on a scale, then measure the volume of the potato by displacement of water.
If I divide those two numbers, have I just measured the density of the potato? Or have I calculated it?

Wikipedia says:
Measurement is the process of estimating the magnitude of some attribute of an object, such as its length or weight, relative to some standard (unit of measurement), such as a meter or a kilogram.

Which makes it seem like combination of measurements do not qualify as measurements.

[anouk]

I don't think this warrants its own thread but heres my question:

What is the scientific definition of measurement, specifically:

If I mass a potato on a scale, then measure the volume of the potato by displacement of water.
If I divide those two numbers, have I just measured the density of the potato? Or have I calculated it?

Wikipedia says:
Measurement is the process of estimating the magnitude of some attribute of an object, such as its length or weight, relative to some standard (unit of measurement), such as a meter or a kilogram.

Which makes it seem like combination of measurements do not qualify as measurements.

hmm... you took some measurements to calculate the density?

[masher]

or have I calculated it?

My gut says you've calculated it.

You've carried out two measurements and then calculated a third result.

[Kodyack]

Ok, my science teacher says everything has a melting point, but wood doesn't melt, it burns. Why doesn't wood melt?

Do we have a melting point?

[eternauta3k]

Wood and people don't melt because they decompose first. If you could somehow keep them from doing that, you would see them melt.

[Sir_Elderberry]

Ok, my science teacher says everything has a melting point, but wood doesn't melt, it burns. Why doesn't wood melt?

Do we have a melting point?

Wood would melt if you heated it up in an oxygen-free environment. Or something. I've read of people doing this and it separates out into individual substances I believe. I want to try this sometime.

[ATCG]

Wood would melt if you heated it up in an oxygen-free environment. Or something. I've read of people doing this and it separates out into individual substances I believe.

You're describing pyrolysis, a process that breaks down and drives off the volatile components of organic matter (such as wood), leaving behind a residue which in the extreme is nothing more than carbon (charcoal). It is the basis for destructive distillation

[justaman]

Besides the burning, it has to do with the fact that wood is made up of many different compounds all intertwined. Wood is composed of fats, carbohydrates, various minerals, in fact, all the components required for plant life, which all have different physical properties and as such different melting points (some are melted at room temperatures).

[smallfried]

I have two questions that have been on my mind and should not be too hard to answer with the right knowledge:

If you put three gyroscopes on orthogonal axes of each other, does the resulting object resist any kind of rotation or do they cancel each other out? If the first, could you use a large version in space to measure rotation of the solar system/galaxy/whatever?

If you rotate a natural magnet at 500000 rotations per second (assuming it won't explode), could you create an AM radio by using shielding that you can vary (rotating half a metal shell at around 440 rotations/sec around it for instance) ?

[drunken]

What do scientists call energy that doesn't cost money? Like energy that you get at work when you plug your phone in to charge it, or energy you get from putting your things in ths sun to dry them, or wehn someone gives you a can or petrol for your birthday. I was confused by the OP for a moment and then I realised why people give me such funny looks when I say that I think it's important to find sources of free energy. I understand exactly what the OP meant of course but I want to be able to talk about 'sources of energy that don't cost money/resoucres/work to collect'. Is there a word for this distinction I could use to avoid confusion around scientists?

[thoughtfully]

If you put three gyroscopes on orthogonal axes of each other, does the resulting object resist any kind of rotation or do they cancel each other out? If the first, could you use a large version in space to measure rotation of the solar system/galaxy/whatever?

It will resist any rotation. Orthogonal forces have no affect on one another; to have any cancellation, there must be an opposing force in the same direction, or at least with some component in that direction.

You can measure the rotation of the Earth with a Foucault Pendulum. In principle, I think it would work for the stuff you mentioned, but the effect would be far beyond anything detectable.

IIf you rotate a natural magnet at 500000 rotations per second (assuming it won't explode), could you create an AM radio by using shielding that you can vary (rotating half a metal shell at around 440 rotations/sec around it for instance) ?

A changing magnetic field will emit EM radiation. You have created a transmitter, not a receiver/radio.

@drunken: maybe power that didn't come from a power company? That doesn't mean it didn't cost money, you know. Solar cells cost money, too. Your "free energy" could be more expensive than what comes from the power company, since they get economies of scale. The cheapest "free energy" is conservation, anyway.

In terms of physical quantities, its all the same. Its an economic distinction, not a scientific one.

[drunken]

@drunken: maybe power that didn't come from a power company? That doesn't mean it didn't cost money, you know. Solar cells cost money, too. Your "free energy" could be more expensive than what comes from the power company, since they get economies of scale. The cheapest "free energy" is conservation, anyway.

In terms of physical quantities, its all the same. Its an economic distinction, not a scientific one.

What you say is true but the problem is not that the economic world and the scientific world are nicely seperate and contained. In fact they are the same world, and while living in them I often talk to people who use the scientific term 'free energy' and also many other people who like to save money. I can't stop scientists from giving me evil looks and thinking I am an idiot when I use the scientific term in the economic meaning. Given that the economic meaning is much older than the scientific meaning it is really not my problem if I cause confusion using the same term for both. I want a new less ambiguous term for the scientific meaning, or a new equally unambiguous term for the economic meaning. A wikipedia search for 'free energy' gives the following:

Science

* Thermodynamic free energy, the total amount of energy in a physical system that can be converted to do work, in particular:
o Helmholtz free energy, the amount of thermodynamic energy in a system that can be converted into work at a constant temperature and volume (called work content in chemistry)
o Gibbs free energy, the amount of thermodynamic energy in a system that can be converted into work at a constant temperature and pressure
+ Free-energy relationship (or linear Gibbs energy relation) help understanding the reaction mechanism for a chemical reaction and makes it possible to predict reaction rates and equilibrium constants.
* Free energy perturbation, is a method based on statistical mechanics that is used in computational chemistry for computing free energy differences from molecular dynamics or Metropolis Monte Carlo simulations.

Conspiracy theory

* Free energy suppression, the notion that special interest groups deliberately suppress technologies that may provide energy at very little cost

So it seems relatively simple to me: unless one of the terms 'thermodynamic free energy' 'Helmoltz free energy' 'Gibbs free energy' or 'free energy pertubation' or some similar scientific quantifier then we can assume that the speaker is referring to the economic/social concept of energy that costs nothing to harvest. A lot of people confuse this with cheap energy but that is something else again.

edit (@oxoiron): I already gave examples. Here is another. I am lying on the ground, I am cold, I need energy to get warmer. Then the sun comes out from behind a cloud and I am warmed. Where is the cost?

PS I am going to leave this now I feel like I am derailing what looks like a very useful thread. If I think of more things to say I'll make a new thread and link it here

[oxoiron]

So it seems relatively simple to me: unless one of the terms 'thermodynamic free energy' 'Helmoltz free energy' 'Gibbs free energy' or 'free energy pertubation' or some similar scientific quantifier then we can assume that the speaker is referring to the economic/social concept of energy that costs nothing to harvest. A lot of people confuse this with cheap energy but that is something else again.

I will grant that cheap energy exists (at least relative to other forms of energy), but I can't think of any form of energy that costs nothing to harvest.

[TheQuestion]

Regarding the uncertainty principle:

If I measure the position( and I don't know its momentum) of something with light of wavelength X, does that mean that
my uncertainty in it's position is literally +/- the wavelength? Or is that a simplification of the uncertainty principle?

[Teppic]

Regarding the uncertainty principle:

If I measure the position( and I don't know its momentum) of something with light of wavelength X, does that mean that
my uncertainty in it's position is literally +/- the wavelength? Or is that a simplification of the uncertainty principle?

Thats not really the uncertainty principle. That's an empirical resolution issue. You're measuring the position of something rather like the way sonar or bats work; a reflected wave bounced off a moving object. You are quite correct though that the theoretical limit of the certainty gained from this is the length of the wavelength.

You stated why this is not an uncertainty issue (I believe if you worked through the definition it would be part of the reason of the wavelength limit) because you are only measuring one variable. position not momentum. rather than position and momentum.

[Teppic]

What do scientists call energy that doesn't cost money? Like energy that you get at work when you plug your phone in to charge it, or energy you get from putting your things in ths sun to dry them, or wehn someone gives you a can or petrol for your birthday. I was confused by the OP for a moment and then I realised why people give me such funny looks when I say that I think it's important to find sources of free energy. I understand exactly what the OP meant of course but I want to be able to talk about 'sources of energy that don't cost money/resoucres/work to collect'. Is there a word for this distinction I could use to avoid confusion around scientists?

I dont know about the scientist bit, but the term bandied about is "over unity" IE it has an efficiency of >100%. Example being a matchstick. When you strike a match (kinetic energy) you get more energy out (heat, flame) than you put in...

If you found matches naturally in nature.

[drunken]

I have another question:

What online resources do people here use for science related stuff. If I want to write a serious thread or post I want to know my facts are right. Also if someone else makes some claim like "it is scientifically possible to cook eggs by singing to them" and qoutes some scientific study, how do I find either the study they are referring to or another one that contradicts or confirms their claim.

The best resource I know of is wikipedia and thats a pretty sad thing to say from a scientific perspective. That or putting very specific terms into google which usually requires a great investment of time to get results from.

[Minerva]

I don't think this warrants its own thread but heres my question:

What is the scientific definition of measurement, specifically:

If I mass a potato on a scale, then measure the volume of the potato by displacement of water.
If I divide those two numbers, have I just measured the density of the potato? Or have I calculated it?

Wikipedia says:
Measurement is the process of estimating the magnitude of some attribute of an object, such as its length or weight, relative to some standard (unit of measurement), such as a meter or a kilogram.

Which makes it seem like combination of measurements do not qualify as measurements.

It's what you'd call an indirect or inferential measurement.

[drunken]

The best resource I know of is wikipedia and thats a pretty sad thing to say from a scientific perspective.

Wikipedia is actually pretty accurate for most stuff that you need to discuss..

There is a lot of stuff that simply isn't covered by wikipedia. Especially research that is either too old or to specialised in certain sub field.

Here is an example. I was reading a book, written by a scientist (S. W. Tromp) in the late 40s. The author is not listed on wikipedia, neither is the book.
I have many questions about this book and the facts that it mentions. The part I want to read more about the most is where he talks about 'electro magnetic phenomena connected with organic processes'. I found one article on wikipedia that vaguely related: biophotonics, but I was interested in really getting down to how research had progressed since the book was written.

If there is no real internet resource for this sort of thing (a google search turns up stuff about altrnative medecine with electro-magnetic fields and similar stuff about the health effects of overhead powerines and so forth) would it be acceptable for me to post a thread in this science forum simply asking 10 or 15 scientific questions? I don't want it to seem like I am too lazy to do my own research and am just using other people for it. But I really tried and also no one here can help me do it better for myself.

[Minerva]

Ok different topic now. I've just decided to get aluminium from the metal work room at school.

Now, this afternoon, just for shits and giggles I decided to put some bleach in a jar, put some water in, and chuck in a couple of iron rods that are connected to an AC adapter. Almost instantly the positive rod started bleeding some orange precipitate everywhere and the negative one started fizzing.
I predicted the fizzing, but this precipitate isn't something I predicted. I've looked through google for something to do with this, but didn't see anything that made sense. So here is my question. What is this orange precipitate? And it's probably a good idea to make sure the gas coming off is Hydrogen. I'm sure it isn't Chloride, because I don't start gagging and dying when I inhale it.
2NaOCL + 2Fe + 2H₂O ==> 2NaOH + H₂ + 2FeOCl is all I can think of, although it's probably wrong.

EDIT: I have just stopped the reaction now. I have done some testing to confirm the liquid in the container is a base of some sort (aka I stuck my finger in and it went all soapy).
Also for added information. Liquid is transparent and smells funny, closest I can think of is bleached lemons perhaps?
Precipitate is Copper coloured.

Have you ever formally learned about electrochemistry? Look at a table of electrochemical potentials, and see if you can work out the reactions that will go on, which might look roughly like this:

Fe(s) ---> Fe²⁺(aq) + 2 e^-

2  H₂O(l) + 2  e⁻ ---> H₂(g) + 2 OH^-(aq)
2 ClO^-(aq) + 2  H₊(aq) + 2  e⁻(aq) ---> Cl₂(g) + 2 OH^-(aq)

Are you sure you're not getting Cl₂? Perhaps the bleach has got some perfume crap in it which masks the smell?

There are three gases you could possibly get - hydrogen, oxygen and chlorine, and you should be able to prove the identity of the gas if you can collect a sample.

[anouk]

I have an odd question, probably silly to anyone who knows anything on the topic.

So when you drink alcoholic drinks, the ethanol gets absorbed into your blood stream, your kidneys filter it out... blahdy blahdy blah, does that mean that you would have alcoholic urine?

[thoughtfully]

Alcohol is not excreted by the kidneys. It is metabolized/detoxified, mainly in the liver. Hence too much drinking being bad for your liver. Cue the disgusting pics of splotchy livers affected by severe cirrhosis.

[Mr_Rose]

I have an odd question, probably silly to anyone who knows anything on the topic.

So when you drink alcoholic drinks, the ethanol gets absorbed into your blood stream, your kidneys filter it out... blahdy blahdy blah, does that mean that you would have alcoholic urine?

In normal humans, ethanol is metabolised first into acetic acid via acetaldehyde (the same process that turns wine into vinegar) and then Acetyl-CoA which is neatly inserted into the Krebs cycle and eventually converted into CO₂ and H₂O. The problem here is the acetaldehyde, which is volatile and can form free radicals. Which is how cirrhosis occurs - too much alcohol vs too few antioxidants = radical damage to cells, potentially causing mutation and cancer but usually just cell death.

[anouk]

Cool, thanks guys, very interesting.

[eternauta3k]

I have an odd question, probably silly to anyone who knows anything on the topic.

So when you drink alcoholic drinks, the ethanol gets absorbed into your blood stream, your kidneys filter it out... blahdy blahdy blah, does that mean that you would have alcoholic urine?

A small percentage is excreted through the kidneys, another part through the lungs. Most of it is metabolized like they said. So yeah, alcoholic urine.

[The-Rabid-Monkey]

Ok I was once again messing around with electricity and substances in a ionic solution and did this.
I had a steel nail connected to positive terminal, a Copper doorhinge connected to negative terminal.
The solution was high mol.L^-1 saline solution.
I put the nail and doorhinge in and flicked on the power. The nail bubbled away furiously for ages, a flame held over the jar grew quite large. I didn't notice any chlorine smell or anything.
I now have a container of dark blue precipitate and setting on top, is an orange precipitate. I'm still evaporating the liquid off.
My question, what were the reactions???
In the container was steel, Cu, NaCl, H₂O and a shit load of electric current.

[oxoiron]

I'll bet you anything that the orange precipitate is rust. The blue precipitate is most likely a copper complex, but I don't have time right now to look up which of the possible options is/are insoluble.

The flame was produced when the electrons from the iron reduced the protons in water and the resulting H₂ ignited as it left the solution.

EDIT: Are you sure the hinge is actually copper?

[thoughtfully]

It's probably brass, so copper and zinc.

Funny, I was wondering if the nail was galvanized, but I guess there could be zinc at both ends

Also, a steel nail will have carbon, and sometimes other stuff like chromium in it.

[The-Rabid-Monkey]

Yes the hinge is copper.
And I didn't really think about the nail being galvanized, but yes it is.
I sort of had an idea the orange precipitate was rust. The main question I suppose was, does any one know what on earth the blue one was? I figured it had copper in because it's blue, duh, but none of the possible ones I can think of are a deep dark blue like this.

[oxoiron]

The main question I suppose was, does any one know what on earth the blue one was? I figured it had copper in because it's blue, duh, but none of the possible ones I can think of are a deep dark blue like this.

If the precipitate is a fine powder, it will look much darker than if it is crystals large enough to be seen with the unaided eye. I've synthesized lots of blue, green and violet crystals that are so dark in powder form that they look black.