exchemist
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Posts posted by exchemist
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42 minutes ago, HarvianRoid said:
Hi, currently I also do some experiments with NaOH, just looking for info here and found this topic. About a year ago, I also disassembled fireworks, so that silvery stuff in your fireworks that reacts with NaOH is probably an alkali metal, like strontium or lithium or more likely aluminum. These guys are famous for their shiny look, how they react with bases like NaOH, and for making fireworks light up in different colors. The black stuff left behind? That could be an oxide. As for the gas, it might be hydrogen or something with sulfur in it. If you're still not sure, I'd say hit the books or read some online materials like https://edubirdie.com/docs/harvard-university/chem-40-inorganic-chemistry you're never too old to learn, trust me! Just remember to be careful when messing around with chemicals and stick to the safety rules. It is better to be more careful with flammable substances (unfortunately, I know this from my own experience) But I think in general it's a problem to find information about it on the Internet, because fireworks are easily accessible and therefore become a great material for research
Not an alkali metal, as all of these react pretty violently with oxygen in the air.
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5 hours ago, user801028 said:
Thanks both. Your information made me see it is probably better to just go for the glass made for the job. I also learned a new thing in thermal expansion. When I was looking at the ads for the stove glass again I suddenly did notice thermal expansion mentioned for one and lauded at "nearly 0%".
0% is interesting. There may I suppose be special "stove glass" with an expansion coefficient even lower than Pyrex. Anyway yes, thermal expansion of a part in the middle of a plate, that is hotter than the periphery, will tend to make it bow up or down, or twist, to relieve the strain - i.e. warp. One other thing: glass is a good thermal insulator. So the glass top may also protect whatever is underneath from getting too hot.
Anyway, glad you found the comments helpful and good luck with the repair.
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7 hours ago, Chemysrylation said:
What data banks do they use when they mix perfumes and use acids so they know how high they can go in their concentrations?
What data banks do they use when they make prank sprays that smell bad?
Is there anybody here who knows anything about it or who else could I ask?
Grateful for any hints because I am currently clueless. ❔❓
Well I suppose you could get the MSDS for a start. There will generally be information about eye irritation and inhalation on those. But you may have already done that.
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17 minutes ago, Silverstreak said:
I know that there is Einstein's equation that relates energy and matter. However, I was curious about what would occur if there was a universe where light didn't exist. Assuming that's even possible, would there be any relationship between matter and energy or would they be completely separated? Would they fail to exist in such a place? Thank you for indulging my curiosity.
The relationship would still exist, I think, since both energy and mass are properties of matter that do not depend on light. By the way the equation does not relate energy with matter: it relates energy with mass. That distinction is important.
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7 minutes ago, Sensei said:
You have AOSP. You can download, install, compile, upload your own OS, and modify it the way you want it to work..
Are you living under a rock?
https://www.google.com/search?q=siri+listens+to+everyone
Say "Hey, Siri" or "Hello, Google," etc.
If the app is open, the microphone has to listen to everything to detect your words.
You don't have Siri or equivalent, permanently active, in your TV though, do you?
Obviously if you have Siri active, you have chosen to have it listen to your voice for commands. What this is about is having an IT system listen to (and send data on) your voice without your consent.
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6 minutes ago, StringJunky said:
Some TVs have 5 or more microphones in them, listening for keywords. Ditto other devices.
Do you know that ? I should have though that could be grounds for a lawsuit for invasion of privacy. Can I read about this somewhere? (As it happens, I don't have a TV, but I think it would be scandalous if true.)
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2 hours ago, swansont said:
My reading of the OP is not about the content, it's the fact that they are full-page rather than banner. I don't know if that's affected by which browser you use.
It's a new feature on a number of forums I subscribe to. It started about a year ago, I think. When you attempt to navigate between threads, or return to the home screen, you sometimes - not always - get instead a full page ad, which you have to cancel before you can see the screen you want. For what it's worth I'm on Apple with Safari as my browser.
What makes it newly tiresome for me is this aggressively advertised Chinese outfit TEMU, presenting you with a totally random range of crap, sometimes including completely unidentifiable objects. I've no idea who these people are - a sort of Asiatic Amazon perhaps? - but they are of zero interest.
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27 minutes ago, MSC said:
Actually that makes sense. My ex converted to the church of latter day saints and I've hosted their missionaries for dinner and sometimes had to google something to do with their beliefs. It's not you science forum, it's me.
Sometimes I swear the algorithms are getting data from our phones mics though, there have been more than a few occasions where we have definitely not keyword searched or clicked on anything related to something we've talked about and all of a sudden... it pops up, unless it can also make predictions about what people are going to be thinking or discussing? Either prospect is creepy as hell.
Actually that suspicion about phone mics is something I have also heard from other people. Either it's just a meme or there is something in it. Perhaps we should look the topic up on the web, oh wait ..........
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7 hours ago, user801028 said:
Maybe a rudimentary question for yall but was not getting much useful information from diyers.
I have a cooktop in a van with the normal heat resistant glass but due to the bumping around when driving as well probably to poor design quality of the glass it cracked.
Rather than replace with another glass one which is liable to crack I thought why not replace with metal instead.
The size I want is relatively small at 29x29cm. Thickness 1-3mm will do.
In my naivety I did not consider the issue of warping at all and just bought standard 3mm mild steel since it was cheaper.
Placing the metal in the recess and firing up the cooker the appliance didn't even have a chance to get through its run up cycle to reach full heat and the metal was already bending. At first I wondered what on earth was happening when I saw it raising off the ground then I twigged it was warping from the heat. This also caused diesel fumes, as that is what it runs on, to bellow out so I had to shut it down quick.
Now I still have the option to use glass which is made for the job of withstanding cooking heat but if there is some metal that will resist the bending under cooking temperatures, I suppose a few hundred Celsius, then metal would still be preferable due to lack of breakage factor.
As I thought and read a little more I realized stainless steel is used for much cookware and that doesn't warp. Also bbq and fast food cooktops I noticed use some kind of sheet metal where they fry stuff right off the cooktop so there must be some metals which will withstand it. Is that likely stainless steel too? Price wise it also seems not too much more than normal mild steel. So will that suffice? It really does have to be well resistant to bending because once placed on the cook surface, after testing it works, it will have to be sealed with heat resistant sealant to keep the fumes contained in the burn chamber and vented out. So it must maintain its form under constant heat and over time.
Will stainless steel still be suitable given those requirements or is something else better, again, considering price? It should be at most as much as a ceramic/glass cooktop which comes to about 40-80 gbp for the size I want.
I'm no expert in this area but I'll have a go, to start off the discussion.
I presume the warping you refer to is due to thermal expansion of the metal, in those areas where it gets hot, whereas the rest of it stays cool. There is a table of coefficients of thermal expansion here:
https://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html
According to this, the coefficient for stainless steel almost double that of mild steel, so it would be expected to expand more with heat and warp more. This is just for metals but here is one that includes glass: https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
According to this, plate glass is similar to stainless steel while unqualified "glass" is similar to mild steel.
Given that glass is brittle, it will crack if it experiences too wide a temperature variation across the specimen. That being so I am wondering what the design of this cooker is and whether you may have inadvertently removed something that avoids a large temperature differential from being created, or else you have not included a gap, or cut, or flexible fixing, somewhere, that permits differential thermal expansion.
Alternatively it may be a question of thickness. Frying pans are commonly made of steel and cheap ones can bow upward in the centre if they are too thin. However better quality ones (heavier, thicker ones) seem not to, presumably because they can contain the thermal stresses within the metal without bending appreciably.
Regarding glass if, it was not just glass but Pyrex, this has a lower coefficient of expansion (~3 x 10⁻⁶mm/mm/ Cdeg) than any of the above materials and can be made thicker and a lot more thermally resistant.
P.S. cross-posted just now with @swansont
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1 hour ago, MSC said:
Some of the ads are also pretty... tasteless or just don't fit the venue of a science forum. I had one telling me my guardian angel was watching over me, but since it was an ad I couldn't comment asking it to provide hard evidence of angels.
no fair!
I don't think whatever algorithm selects the ads to display considers the forum they are displayed on. It's probably much more to do with what it thinks based on whatever it has gleaned about your browsing and on-line purchase history. Since I do what I can to minimise this , e.g. via blocking trackers, I get weird ad selections: funeral services, drilling machinery, women's fashion and ads in Chinese characters. (When I looked up a few words in Dutch for another forum, I started getting Dutch websites popping up on my search engine too - it's all rather creepy.)
All a bit baffling and annoying, but I tell myself the alternative would be that we would have to pay a subscription for a forum like this, so it doesn't do to grumble too much.
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4 hours ago, TheVat said:
Tired of harassment-level ads that constantly drop over the page one is trying to navigate to. Is there a way to get some feedback to @blike and go back to the usual banner ads or other formats one can scroll past? Does anyone really think they're going to sell a product by shoving it in our cyber-faces over and over? I would think there is an inverse relationship between rudeness of ads and sales generated. SFN is better than this.
And no, I don't want to change my wifi provider, thanks.
This looks like another example of “enshittification” : https://en.wikipedia.org/wiki/Enshittification
Cory Doctorow gave an excellent lecture on this in January. Here is a link to the transcript. It’s very well written, rather in the style of Michael Lewis’s Liar’s Poker: https://doctorow.medium.com/my-mcluhan-lecture-on-enshittification-ea343342b9bc
Long, but very readable - and worth the read.
He muses that we may be entering the enshittocene era.
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1 hour ago, Sensei said:
Philosophy is a pseudoscience. Physics is a real science. Too often you ask philosophical questions.. ask physical questions, such as "how to measure the speed of something", "how to measure some physical quantity", etc., and you will get the right, truthful answers..
..one water molecule hits another molecule, which hits another molecule, and there is a momentum transfer between them in all directions, they hit something, while molecule remain at place (plus, minus, a little margin of tolerance (in global scale) )..
They are called photons..
Philosophy is not a pseudoscience.
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13 minutes ago, KJW said:
Hmmm. I'm actually somewhat surprised that in the fusion from hydrogen to iron, the first step to helium provides about 80% of the energy (or am I interpreting the diagram incorrectly?).
That's how I interpret the diagram. Though one has to keep in mind this is binding energy per nucleon. What intrigues me, not being a nuclear physicist, is the spike at helium, and the smaller one at oxygen. These elements seem to have stability that lies off the curve. Are they filled nuclear shells or something?
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9 hours ago, ALine said:
Is there a metal out there you can bombard with electrons to get gamma radiation?
I don’t think so.
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2 hours ago, ALine said:
No, I am turning alpha particles into a proton pair and then waiting for them to fuse by applying energy.
If you have a naturally decaying radioactive source such as C-60 which emits gamma radiation then you would not need to worry about input energy. Its just naturally supplied.
But what's the point? All you do is make deuterium, which we can easily extract from seawater anyway, from alpha particles, by a process with <0.01% efficiency that consumes a lot of energy however it is supplied. What have you achieved? A net fission of helium into deuterium. What use is that?
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16 hours ago, jajrussel said:
Okay, I was thinking for the first question that if both ma and GMm/R2 equaled force I could write it F=ma=GMm/R2 . Which is not exactly how I wrote it the first time but I borrowed the shorthand from swansont for the latter portion. What I thought I was writing is force equals mass time acceleration ,and force equals G times mass one times mass two divided by the radius squared. Since force is described as equal to both expressions. I assumed it would be okay to write F=ma=Gmm/R2 since the expression on each side of the equal signs I presumed to be equal.
As for the second question.Are you saying that by canceling mass out, force and acceleration are shown to be the same?
As the little "m" s appear once on each side of your equation you can cancel them, but that leaves the big M. So the "a" in F=ma should be set equal to GM/r².
There has to be an M in it because the acceleration due to gravity depends on whether you are standing on, say, the Earth, or the Moon which has less mass and therefore weaker gravity. Newton's expression is completely general and can be used for any body, dialling up and down M according to the mass of the body in question.
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53 minutes ago, ALine said:
how much does it cost to remove a neutron?
Irrelevant. All you need to know is the binding energy per nucleon of the reactant species at the start and of the product species at the end and do the arithmetic. The route by which you carry out the change has no effect on the overall energy change between the two.
What you are proposing is the reverse of the fusion people are trying to achieve with Tokamaks etc. You are turning a helium nucleus into 2 deuterium nuclei rather than the fusion process of turning 2 deuterium nuclei (or one deuterium and one tritium) into helium. Since that process releases energy, which is why people are trying to do it, your proposed process must necessarily absorb the same amount of energy.
The binding energies per nucleon are shown on this graph, which shows the enormous gap between ²H and ⁴He:
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22 minutes ago, mcstroom said:
I was not expecting that awnser. It depends on the reaction I am doing. Wow. I'am doing many reactions. There are many.
-Alchols recting with acidified di chromate
-Alchols reacting with hot sulfuric acid
-oxidation and reaction reactions
-acetic acid reactions etc
The way I understand is that the product that that used to be a reactant and had the nucluphile has to have no formal charges but evreything else that was formed by leaving groups can have a formal charge. How far away I am from being correct
What you are now writing seems to have no connection to your original question. A discussion of reaction mechanisms and formal charges seems to have nothing to do with how you can tell that a reaction is complete or not.
I can't comment any further unless you can be clearer about what you are trying to do.
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55 minutes ago, mcstroom said:
What indication is there that a organic chemistry reactions is finnished
I think that will depend on the reaction in question, won't it? Do you have a particular type in mind?
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12 hours ago, mcstroom said:
I thought that you keep on doing attacks untill you give evrey atom its proper valance electrons but according to the reaction in the video I saw I was wrong so can someone please help.
The pictures don't help without a lot more explanation. What are you talking about?
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12 hours ago, Zenith29 said:
Though there is a lot of importance given to renewable energy but is it really not the solution to energy problem because
nich market and a tough competition with existing fossil fuel industry
it is still expensive
Is not 100% reliable
Your premise appears to be false. Renewable generation is now competitive with fossil fuel electricity production: https://www.weforum.org/agenda/2020/06/cost-renewable-energy-cheaper-coal/
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2 hours ago, ALine said:
It shows that the resultant of fusion is not beta(-) decay but instead beta(+) decay.
But that process has nothing to do with the one you were asking us to consider. What you were proposing was conversion of ²He into D. That process, which is only followed in <0.01% of cases, is indeed β+ decay, but it is not fusion.
The net conversion achieved by your proposal, starting from α-particles, is ⁴He -> D. This is a convoluted fission process, not fusion and, surprise, surprise requires a net input of energy to achieve it.
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56 minutes ago, ALine said:
But it also says that there is a <0.01% decay into 2H through beta decay.
Yup, so 2/10 of F-all .
You think you can run a viable fusion reactor on that basis?
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56 minutes ago, ALine said:
No I mean that if you remove the neutrons in the alpha particle the protons would be close enough to allow for the protons to fuse. That is done using gamma radiation from a natural source. It would then form deuterium and not helium-4.
If you consult the table in the link I provided, you will see >99.99% decay into 2 x 1H, i.e. the 2 protons just fly apart.
52 minutes ago, ALine said:isn't He-2 isotope decaying into H-2(deuterium) just fusion?
But it doesn't.
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Tell me true or false?,,,,,,why?
in Religion
Posted
Is what true or false?