First post, hello, I have a lot of questions.

[MigL]

Chemical compounds can be separated into 'functunal' groups.

There are acids, a sour, easily wetted substance, readily soluable in water, with an acrid smell that irritates mucous membranes, and turn litmus indicator red.
These react with bases, bitter, slippery and also water soluable, but turn litmus blue.
In modern chemistry, their solutions decompose to OH- ions and H+ ions; the log scale of their ratio gives the pH value you may have heard of.

Two other groups are oxidizers and reducers, which also react with each other, like the previously mentioned hydrazine ( reducer ) and nitric acid ( oxidizer and an acid ) used by the Germans as propellant for their WW2 rockets.
The reaction of these groups, redox reactions, are used to produce chemical energy. Think of the lead and acid in your car battery, the carbon and oxygen of a fire, or the oxygen and hydrogen that produces the thrust of a modern orbital rocket. One of the elements in the compound provides a lower energy state for one or more electrons of the other element's higher state, and this is released as useable energy.

There are other groupings that help distinguish, such as inert, or noble gases, that don't react with others, metals which have a conduction band of electrons above the valence band ( where chemical bonds are made ) and can conduct electricity and orient into magnetic domains, and even one group you may be hearing about in the news, as the American President is extorting Ukraine for its valuable rare earth elements,

Such groupings of similar properties help identify what you are dealing with, or give direction for further testing that will.

Edited Saturday at 09:58 PM by MigL

[studiot]

Just now, Jack777 said:

"Metal ions in the form of chloride salt solution with platinum wire." Now, I know I'm thick, I really am. How in the world did he know it was chloride and how did he know it was platinum? These are what I'd like to know. 

 

Just now, Jack777 said:

Cool. Now, how do they know it's acid?

Sorry for so many newbie questions but this is what I've always wondered about. The simplest most fundamental questions.

No you are not thick and these are basic questions, which as you say, are fundamental.

But they are very good questions.

Don't worry we are covering these.  I hope you are taking in the new terminology. I am trying not to introduce too many new words at once.

So I think we are ready for your first chemical equation

 

ACID  plus BASE  =  (makes)  SALT plus WATER

Note that chemical equations are somewhat different than mathematical ones, although we will come to do some mathematics with them.

Such a chemical equation represents a chemical reaction (or in this case a whole class of chemical reactions)

 

So we have Hydrochloric Acid  plus Sodium Hydroxide makes Sodium Chloride plus Water.

Acids were once called spirits and hydrochloric acid was called spirits of salt.

Sodium hydroxide has a common name as caustic soda. 

So our friend either made the chlorides this way or bought them ready made.

I think MigL has described acids quite well for you. if that is not enough please ask for more.

The 'salt' created by hydrochloric acid is called a chloride.

Why chlorides ?

Well most chlorides are (very) soluble in water. That's how the presenter got the solutions.

There are always exceptions the main ones being the chlorides of silver, lead and mercury are hardly soluble.

 

So next bit of theory.

Solutions are made by dissolving a solute (sugar, salt etc) in a (suitable) solvent.

Thinking back to our earlier posts a solution is a mixture because the parts can be separated by mechanical means boiling off the solvent to leave the solute behind.
This process is called distillation.

Another similar sort of mixture is called a suspension. Here fine particles of one substances is intimately mixed with another  substance. The result is called a suspension.
This is not solution, although the suspended particles may be recovered by boiling, they may also be recovered by passing the suspension through a sufficiently fine filter.

Finally (for this post) we can also separate the solute (or part of it) by a Precipitation Reaction.

Here we take a solution of an obviously soluble salt and add a solution of a different salt which will react with the salt already in solution in such a way as to produce a Precipitate.

This happens when the added new solution contains ions that are insoluble as a salt of the original solute.

As an example we now know that silver chloride is insoluble, and I am now stating (from experience) that silver nitrate is soluble.
So if we add a soluble chloride (such as sodium chloride) to a silver nitrate solution we we observe a (white) precipitate - of silver chloride.
In effect the sodium and silver exchange their type of salt.

This sort of reaction is important in both analytical chemistry and for the preparation of chemical compounds.

The silver chloride can be filtered off or used in a second reaction as in the video.

We are now building up chemical vocabulary to use in the future.

 

 

 

 

Edited Saturday at 11:08 PM by studiot
post appeared double.

[Jack777]

4 hours ago, exchemist said:

That's quite a lot already

Right. Protons, neutrons, electrons, I can understand that despite not seeing it but I take it on faith.

Atomic number and atomic weight, and isotopes. I still need a lot of work here to learn this.

Avogadro's Number and moles -  This might take me centuries to understand.

I like the study of combustion so far.

 

3 hours ago, MigL said:

Chemical compounds can be separated into 'functunal' groups.

Excellent information here but it'll take me a while to "get it." Sadly I'm aspergic so it takes me a while to grasp something but once I do it's grasped forever.

 

2 hours ago, studiot said:

No you are not thick and these are basic questions, which as you say, are fundamental.

But they are very good questions.

Don't worry we are covering these.  I hope you are taking in the new terminology. I am trying not to introduce too many new words at once.

So I think we are ready for your first chemical equation

I very much appreciate your help. And thanks for your kind words.

Yes, I have so far copied all my questions and your posts and created a document which I think I need to read and reread constantly. It's very good stuff. 

I don't think I'm ready for an equation.  About all I know is what most people know and that's H2O. One hydrogen and two oxygen. But my perennial questions are always like, ok, one hydrogen, how do they actually know it's hydrogen? Ditto for oxygen and how do they know you only need one hydrogen and two oxygen. We really need to back up and get even more basic. Like kindergarten basic  

How was hydrogen first discovered? How was oxygen first discovered? I mean, what process did they use to discover them? Was it weighing? Burning? Dunno.

But I find this absolutely fascinating. I can tell you anything you'd want to know about aircraft, how they work, how to fix them, how to fly them, same for woodworking. But chemistry? Not so much. I love studying history so anything history related in regards to who and how and when would be very helpful.

In the video you posted, he said silver nitrate. Where did he get it and how is he sure it's silver nitrate?

Same for silver chloride. How does he know it's silver chloride? And what's silver chloride used for anyway? This is so interesting!

[KJW]

57 minutes ago, Jack777 said:

he said silver nitrate. Where did he get it and how is he sure it's silver nitrate?

He probably got it from a chemical supplier, and he knows it's silver nitrate probably because that's what it says on the label of the bottle it came in. My point is that modern day chemists do not start from scratch. They (to use a well-known quote) stand on the shoulders of giants. It should be noted that knowledge of chemistry developed over time and in parallel with knowledge of physics.

I think that the scope of your questions is too large for anyone here to provide you with genuine help, as much as they may try. I recommend that you study a chemistry textbook aimed at school children. However, you may find this Wikipedia article interesting (though I haven't fully read it myself):

https://en.wikipedia.org/wiki/History_of_chemistry

 

[exchemist]

11 hours ago, MigL said:

Chemical compounds can be separated into 'functunal' groups.

There are acids, a sour, easily wetted substance, readily soluable in water, with an acrid smell that irritates mucous membranes, and turn litmus indicator red.
These react with bases, bitter, slippery and also water soluable, but turn litmus blue.
In modern chemistry, their solutions decompose to OH- ions and H+ ions; the log scale of their ratio gives the pH value you may have heard of.

Two other groups are oxidizers and reducers, which also react with each other, like the previously mentioned hydrazine ( reducer ) and nitric acid ( oxidizer and an acid ) used by the Germans as propellant for their WW2 rockets.
The reaction of these groups, redox reactions, are used to produce chemical energy. Think of the lead and acid in your car battery, the carbon and oxygen of a fire, or the oxygen and hydrogen that produces the thrust of a modern orbital rocket. One of the elements in the compound provides a lower energy state for one or more electrons of the other element's higher state, and this is released as useable energy.

There are other groupings that help distinguish, such as inert, or noble gases, that don't react with others, metals which have a conduction band of electrons above the valence band ( where chemical bonds are made ) and can conduct electricity and orient into magnetic domains, and even one group you may be hearing about in the news, as the American President is extorting Ukraine for its valuable rare earth elements,

Such groupings of similar properties help identify what you are dealing with, or give direction for further testing that will.

All good info, save that this is not what a "functional group" is in chemistry. That term is used in organic chemistry, to denote groups of atoms which are part of an organic molecule, conferring specific types of behaviour, or functionality. Examples would be amine groups or carboxylate groups. Acid/base and redox classifications would not be described as functional groups. More here: https://en.wikipedia.org/wiki/Functional_group

 

8 hours ago, Jack777 said:

Right. Protons, neutrons, electrons, I can understand that despite not seeing it but I take it on faith.

Atomic number and atomic weight, and isotopes. I still need a lot of work here to learn this.

Avogadro's Number and moles -  This might take me centuries to understand.

I like the study of combustion so far.

 

 

I very much appreciate your help. And thanks for your kind words.

Yes, I have so far copied all my questions and your posts and created a document which I think I need to read and reread constantly. It's very good stuff. 

I don't think I'm ready for an equation.  About all I know is what most people know and that's H2O. One hydrogen and two oxygen. But my perennial questions are always like, ok, one hydrogen, how do they actually know it's hydrogen? Ditto for oxygen and how do they know you only need one hydrogen and two oxygen. We really need to back up and get even more basic. Like kindergarten basic  

How was hydrogen first discovered? How was oxygen first discovered? I mean, what process did they use to discover them? Was it weighing? Burning? Dunno.

But I find this absolutely fascinating. I can tell you anything you'd want to know about aircraft, how they work, how to fix them, how to fly them, same for woodworking. But chemistry? Not so much. I love studying history so anything history related in regards to who and how and when would be very helpful.

In the video you posted, he said silver nitrate. Where did he get it and how is he sure it's silver nitrate?

Same for silver chloride. How does he know it's silver chloride? And what's silver chloride used for anyway? This is so interesting!

I don't understand your question about silver nitrate. This video does not relate to the dawn of chemistry in the c.18th, when there were real issues with correctly identifying the substances they worked with. For the last 100 years at least, people have been able to obtain chemical compounds from commercial suppliers.

Are you serious or are you messing us about?

[studiot]

5 hours ago, Jack777 said:

I don't think I'm ready for an equation.  About all I know is what most people know and that's H2O. One hydrogen and two oxygen. But my perennial questions are always like, ok, one hydrogen, how do they actually know it's hydrogen? Ditto for oxygen and how do they know you only need one hydrogen and two oxygen. We really need to back up and get even more basic. Like kindergarten basic  

H2O is a chemical shorthand formula. It is not an equation. Equations have and equals sign, so some formulae but not all,  are also equations.

Equations do not need to use shorthand symbols, they can be much easier without when you first start using them.  This is why I haven't yet got to symbols, atoms, molecules etc. You need some basic stuff to work with for those symbols to have any meaning.

So don't worry there is method in my madness and we will get there.

Also I have carfully selected my examples to follow from each other so here goes with some more.  There are two videos and one picture this time.

Many substances occur naturally in the world around us. You asked where their names came from.
As humans began to explore their world they named materials they found around them, particularly those they found to be useful.
This naming started thousands of years ago and is still going on today.

The result of this is that some chemicals with modern names can be simply refined or extracted from our natural world.
Some folks actually make a business of this.

 

However of the 4000 or so minerals that we know of only about 10 are very very common (over 90% of the earth's surface).
The rest are uncommon. Even carbon (which is not mentioned in the next video) is only 0.02% of the Earth's crust.
So I hope the video will show why I am not launching straight into more advanced chemistry including the periodic table, formulae and so on.
These will come, but you need to have a reason to look at them.

 

 

6 hours ago, Jack777 said:

How was hydrogen first discovered? How was oxygen first discovered? I mean, what process did they use to discover them? Was it weighing? Burning? Dunno.

As I said I am following on from previous posts. The discovery of Hydrogen and oxygen and other gases is fascinating, but they made many mistakes in those days so it is better to wait for these.

Finally sliver nitrate.

I mentioned that this is the basis of photography so here is a nice short video about this.

I live near the Fox-Talbot museum, which is a fascinating place to visit.

 

[Jack777]

3 hours ago, exchemist said:

Are you serious or are you messing us about?

I am not messing about! I find that to be very insulting. 

Why would I register on a chemical forum just to mess about? I came here to learn about chemistry. I'm sorry I don't have the body of knowledge you think I ought to have.

Good day sir.

[exchemist]

34 minutes ago, Jack777 said:

I am not messing about! I find that to be very insulting. 

Why would I register on a chemical forum just to mess about? I came here to learn about chemistry. I'm sorry I don't have the body of knowledge you think I ought to have.

Good day sir.

Well, there are funny people about, as those of us who have spent time on these forums know, to our cost. Establishing the bona fides of a new poster takes a bit of time, so you will have to excuse me for being cautious.
 

It was a very odd question for you to ask, that’s all. Why did you ask it? Did you really not realise that chemicals can be bought from commercial suppliers?

Edited Sunday at 02:03 PM by exchemist

[Jack777]

4 minutes ago, exchemist said:

Well, there are funny people about, as those of us who have spent time on these forums know, to our cost. Establishing the bona fides of a new poster takes a bit of time, so you will have to excuse me for being cautious.
 

It was a very odd question for you to ask, that’s all. Why did you ask it? Did you really not realise that chemicals can be bought from commercial suppliers?

Bona fides? What, do I have to pass an exam or something? Do I have to give you my life's history for YOU to be satisfied I'm just a person who's never been taught chemistry.

And yes,I have never in life considered that chemicals can be bought from suppliers. It was never important to me. And I do not find it odd. I'm sorry I don't have the knowledge base you do.

 Maybe it would be better if you let the other guy answer my questions.

[exchemist]

27 minutes ago, Jack777 said:

Bona fides? What, do I have to pass an exam or something? Do I have to give you my life's history for YOU to be satisfied I'm just a person who's never been taught chemistry.

And yes,I have never in life considered that chemicals can be bought from suppliers. It was never important to me. And I do not find it odd. I'm sorry I don't have the knowledge base you do.

 Maybe it would be better if you let the other guy answer my questions.

Don’t be so touchy. On the internet we don’t know who we are dealing with and I’ve got burnt in the past by timewasters, as have many others here.It takes a while to develop a rapport and trust with someone new. That’s what I mean by bona fides. It was a peculiar question for you ask so I became a bit suspicious, that’s all.

But  up to you if you prefer to continue with someone else, of course.

Edited Sunday at 02:40 PM by exchemist

[Jack777]

8 hours ago, exchemist said:

Don’t be so touchy. On the internet we don’t know who we are dealing with and I’ve got burnt in the past by timewasters, as have many others here.It takes a while to develop a rapport and trust with someone new. That’s what I mean by bona fides. It was a peculiar question for you ask so I became a bit suspicious, that’s all.

But  up to you if you prefer to continue with someone else, of course.

Ok, no problem. It's past.

Now, on to my question. That video lost me at silver nitrate. Let's say someone gives me a bottle of silver nitrate, how in the world do I know it's silver nitrate and what's silver nitrate anyway? I imagine it involves getting some silver and some nitrate and combining them? But then down the rabbit hole it goes, how does he know it's actually silver and how does he actually know it's nitrate?

10 hours ago, studiot said:

H2O is a chemical shorthand formula. It is not an equation. Equations have and equals sign, so some formulae but not all,  are also equations.

 

Thanks. I will need a little time to read this and digest it and then I'll be back and reply.

[KJW]

Broadly speaking, you are asking how a chemist knows what a given substance is. In the modern day, we have several instruments that provide spectroscopic data that helps identify the structure of a substance. It should be noted that this depends on the purpose of the investigation. For example, if we simply wish to check that the substance is what it is claimed to be, then one can simply compare a spectrum of the unknown with a spectrum of a known sample. The spectrum itself need not provide much information about the structure because all one needs is that the two spectra be the same, like comparing fingerprints. By contrast, if the substance is truly unknown, then one would choose spectroscopic data that provides useful information about the structure. And different instruments provide different information about different aspects of the structure. For example, a low-resolution mass spectrum tells one the molecular mass of the substance. A high-resolution mass spectrum tells one the molecular formula of the substance. A proton nuclear magnetic resonance spectrum provides information about the environment of each hydrogen atom in the molecule, including couplings to adjacent hydrogen atoms. X-ray crystallography provides what is more or less an actual picture of the molecule, including precise bond lengths and bond angles (though this does require a good quality single crystal of the substance, and substantial computer processing of the diffraction data, and may not provide a complete picture). There is of course a lot more that could be said, but I think the above provides a glimpse into the world of the working chemist.

 

[Jack777]

22 hours ago, studiot said:

Also I have carfully selected my examples to follow from each other so here goes with some more.  There are two videos and one picture this time.

Outstanding! Thanks for these videos. In the first one I never knew most of the Earth's crust was oxygen and silicon. And when he mentions quartz and feldspar I imagine these two as well as most of the 4000 are not on the periodic table but the table of elements make up quartz and feldspar. Very interesting stuff here.

And that second video about the negatives, also interesting. Right, when she said they coated it in silver nitrate, back then how did he know he actually had silver and also nitrate. This is what I think my most fundamental question is about chemistry. Did he burn it back then? How did they actually know?

I watched three YT's about the history of chemistry that were dramatized, they were fantastic. So I've been binge watching more YT's. 

I learned a little about spectroscopy, it was pure genius to pass light through a prims. As someone on the video said each element has its own barcode. I thought this was a cool way of looking at it.

[exchemist]

12 hours ago, Jack777 said:

Ok, no problem. It's past.

Now, on to my question. That video lost me at silver nitrate. Let's say someone gives me a bottle of silver nitrate, how in the world do I know it's silver nitrate and what's silver nitrate anyway? I imagine it involves getting some silver and some nitrate and combining them? But then down the rabbit hole it goes, how does he know it's actually silver and how does he actually know it's nitrate?

Thanks. I will need a little time to read this and digest it and then I'll be back and reply.

I'm still baffled by your question. You know it's silver nitrate because that's what it says on the bottle and you bought it from a reputable supplier.

But if, for instance, some idiot transfers it to an unlabelled bottle, you can confirm it is silver nitrate by carrying out some characteristic reactions with a small sample of it: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Qualitative_Analysis/Characteristic_Reactions_of_Select_Metal_Ions/Characteristic_Reactions_of_Silver_Ions_(Ag)

You can also confirm nitrate by infra red spectroscopy and silver by its visible/UV spectrum: https://www.atomtrace.com/elements-database/element/47     

Is that OK as an answer? I have the feeling I may not quite have grasped the significance of your question.

Edited Monday at 12:14 PM by exchemist

[Jack777]

10 hours ago, KJW said:

Broadly speaking, you are asking how a chemist knows what a given substance is. In the modern day, we have several instruments that provide spectroscopic data that helps identify the structure of a substance. It should be noted that this depends on the purpose of the investigation. For example, if we simply wish to check that the substance is what it is claimed to be, then one can simply compare a spectrum of the unknown with a spectrum of a known sample. The spectrum itself need not provide much information about the structure because all one needs is that the two spectra be the same, like comparing fingerprints. By contrast, if the substance is truly unknown, then one would choose spectroscopic data that provides useful information about the structure. And different instruments provide different information about different aspects of the structure. For example, a low-resolution mass spectrum tells one the molecular mass of the substance. A high-resolution mass spectrum tells one the molecular formula of the substance. A proton nuclear magnetic resonance spectrum provides information about the environment of each hydrogen atom in the molecule, including couplings to adjacent hydrogen atoms. X-ray crystallography provides what is more or less an actual picture of the molecule, including precise bond lengths and bond angles (though this does require a good quality single crystal of the substance, and substantial computer processing of the diffraction data, and may not provide a complete picture). There is of course a lot more that could be said, but I think the above provides a glimpse into the world of the working chemist.

 

Hi KJW, this is an absolutely fantastic explanation, it's very much appreciated! I need to research what these low and high resolution spectrums are though, like what they look like and how they work. 

1 minute ago, exchemist said:

I'm still baffled by your question. You know it's silver nitrate because that's what it says on the bottle and you bought it from a reputable supplier.

But if, for instance, some idiot transfers it to an unlabelled bottle, you can confirm it is silver nitrate by carrying out some characteristic reactions with a small sample of it: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Qualitative_Analysis/Characteristic_Reactions_of_Select_Metal_Ions/Characteristic_Reactions_of_Silver_Ions_(Ag)

You can also confirm nitrate by infra red spectroscopy and silver by its visible/UV spectrum: https://www.atomtrace.com/elements-database/element/47     

The links you sent me with the symbols are so far over my head as to be gibberish. I know you mean well but I get the feeling you assume I have a body of knowledge I simply do not have. When I say kindergarten level I mean just that, idiot level is more accurate. 

And you baffle me with your bafflement. What is it you don't understand about the question I ask? Let's approach it differently.

Say it's 1500 years ago and I was an alchemist and I wanted to make whatever. If someone told me I needed to use silver, or copper, or any other periodic element, how would I be sure those are actually silver or copper?

[exchemist]

32 minutes ago, Jack777 said:

Hi KJW, this is an absolutely fantastic explanation, it's very much appreciated! I need to research what these low and high resolution spectrums are though, like what they look like and how they work. 

The links you sent me with the symbols are so far over my head as to be gibberish. I know you mean well but I get the feeling you assume I have a body of knowledge I simply do not have. When I say kindergarten level I mean just that, idiot level is more accurate. 

And you baffle me with your bafflement. What is it you don't understand about the question I ask? Let's approach it differently.

Say it's 1500 years ago and I was an alchemist and I wanted to make whatever. If someone told me I needed to use silver, or copper, or any other periodic element, how would I be sure those are actually silver or copper?

OK, I didn't expect you to be able to follow all the methods. I just wanted to indicate we have standard ways of identifying these compounds, so that is how it would be done if the question were to arise today with an unknown sample.  

But if what you are after is how these elements and compounds were identified historically, i.e. before modern day analytical chemistry was available, that's a lot trickier. I think I would have to try to explain that by examples. I gave you one example previously, of what Lavoiser deduced from burning phosphorus. He got a lot out of that:

- 2 components of air: azote and oxygene

- A compound (ash) in which phophorus was combined with oxygen (we would call that an oxide, though I'm unsure if the term existed in his time)

- this compound produced an acid when dissolved in water - a phosphorus acid.

Silver, gold and copper were obviously known in the Ancient world for coinage and jewellery and alloys of them. Zinc and tin were also known. Bronze is an alloy of copper with tin (e.g. the Bronze Age) and copper and zinc produced brass.

Mineral acids, including nitric acid, were known to Medieval alchemists (though not under their modern names): https://en.wikipedia.org/wiki/Nitric_acid

So someone in Lavoisier's time could dissolve a piece of silver in nitric acid and realise they had a compound - which today we call silver nitrate.

It's obviously not possible to trace all the stages by which all these elements, reactions and compounds gradually became characterised. It would take a book to do that and even then there would still be plenty of uncertainty about how many of the steps became known. The historical record is patchy and some of thee unknown alchemists guarded their knowledge. But I hope from this you get an idea of the sort of things they did and so how the early chemists were able to piece together some rules for elements and compounds.

In fact, Lavoisier was the first to make a real list of elements and he still got some things wrong. Here's a quote from the relevant Wiki page:  

QUOTE

The book contains 33 elements, only 23 of which are elements in the modern sense.[5] The elements given by Lavoisier are: light, caloric, oxygen, azote (nitrogen), hydrogen, sulphur, phosphorous (phosphorus), charcoal, muriatic radical (chloride), fluoric radical (fluoride), boracic radical, antimony, arsenic, bismuth, cobalt, copper, gold, iron, lead, manganese, mercury, molybdena (molybdenite), nickel, platina (platinum), silver, tin, tungstein (tungsten), zinc, lime, magnesia (magnesium), barytes (baryte), argill (clay or earth of alum), and silex.[6]

UNQUOTE

From: https://en.wikipedia.org/wiki/Traité_Élémentaire_de_Chimie

It was a long and painful process that was only really sorted out in the latter half of the c.19th with Mendele'ev.  

 

 

Edited Monday at 12:46 PM by exchemist

[studiot]

Just now, Jack777 said:

I learned a little about spectroscopy, it was pure genius to pass light through a prims. As someone on the video said each element has its own barcode. I thought this was a cool way of looking at it.

That's really good
We used to call this activity 'reading around the subject'
though nowadays you could call it viewing investigating or whatever.
And you are using the chemical vocabulary you are acquiring.

😀

Let's look at the first chemical equation I wrote for you again, but in more detail.

Acid + Base  =  Salt + Water.

I didn't mention before that there are many different acids; there are many different bases.

The substance that is produced by the acid + base reaction is called a salt.

Sodium chloride is also called common salt, but it is just one of many salts that can be produced.

Each salt is specific to both the acid and base that react with each other to form the salt.

Some salts are water soluble, some are not.

The 'or not' is important because it is often useful to find out and eliminate what a sample is not.

 

Silver nitrate is a salt which is water soluble white salt.

Silver chloride is a white salt that is not soluble in water.

Now you are asking about identification.

So an easy first check is to see what it is not i.e. does it dissolve in water ?

Well we have seen the result of that experiment so we can se that if the white powder that purports to be silver nitrate dissolves in water it could be correct.

But if it does not dissolve the it definitely could not.

This kind of thinking is not only important in chemical analysis, but also in geology since it helps determine what substance could or could not be in a given bunch of minerals.

It is also important in chemical synthesis  - that is finding ways to make a particular chemical substance.

Remember our way of making sodium chloride is the Acid + Base = Salt + Water equation or reaction.

Hydrochloric acid + Sodium hydroxide = Sodium chloride  +  Water.

But this will not work well for silver to make silver chloride because silver hydroxide is almost insoluble in water.

So to make silver nitrate we need a different reaction and obviously with the right acid, this time nitric acid.

Here is a short video of how to make silver nitrate by dissolving pure silver in nitric acid  (This is an exmaple of an oxidation- reduction or redox reaction already mentioned).

I am not suggesting you actually carry it out for safety reasons.

 

After this I think it is time we started putting some flesh on the idea of stuff or matter.

As someone with good knowledge of flight and aviation I hope you understand the difference between weight and mass ?

If not let us know and we will incorporate that.

 

[Jack777]

23 hours ago, studiot said:

'reading around the subject'

Hi, yes, a good description.

Ok, sorry for the delay as I've been busy. 

I watched the video and it looks easy to make and no problem, I have no desire to make it.

However, and here's my question, how in the world did they know it was actually acid back then? And when they found newer ways of making acid how are they sure it's really acid? I know these may seem like stupid questions, sorry. I've been watching a lot of YT's on the history of this but no one has ever showed the most basic things like how they knew it was acid. All the books and videos I have assume that people just know.

Yes, weight is how much something weighs and mass is the density of something. On the moon the astronauts may have weighed 300 pounds with all the gear but the gravity made them feel lighter yet they still had the mass, the momentum of that mass.

[exchemist]

1 hour ago, Jack777 said:

Hi, yes, a good description.

Ok, sorry for the delay as I've been busy. 

I watched the video and it looks easy to make and no problem, I have no desire to make it.

However, and here's my question, how in the world did they know it was actually acid back then? And when they found newer ways of making acid how are they sure it's really acid? I know these may seem like stupid questions, sorry. I've been watching a lot of YT's on the history of this but no one has ever showed the most basic things like how they knew it was acid. All the books and videos I have assume that people just know.

Yes, weight is how much something weighs and mass is the density of something. On the moon the astronauts may have weighed 300 pounds with all the gear but the gravity made them feel lighter yet they still had the mass, the momentum of that mass.

If you go way, way back, I think they tasted them and they were sour. Your tongue can detect acid this way. 
There is a bit of the history here: https://pubsapp.acs.org/subscribe/archive/tcaw/12/i03/pdf/303chronicles.pdf

 

[studiot]

3 hours ago, exchemist said:

If you go way, way back, I think they tasted them and they were sour. Your tongue can detect acid this way. 
There is a bit of the history here: https://pubsapp.acs.org/subscribe/archive/tcaw/12/i03/pdf/303chronicles.pdf

 

 

Well that is an excellent article. +1

And therein goes the material I was going to use for my next post, so I will just pick out the important points that lead to the conclusion I was going to offer.

How we got to our modern view of chemistry can be divided into four broad periods.

The ancients began to notice that there were many different substances in the world around them.

The substances were different because they had different properties. They were hard or soft, some interacted visibly with other substances. Some did not appear to interact at all and some offered protective qualities for other substances.

In particular sometimes winemaking went wrong and an unpleasant sour tasting drink was produced instead of acceptable wine.
They did not know that wine had turned to acetic acid but their word for vinegar (which is dilute acetic acid) passed down into the Latin word 'acidus' and from there into English as acid.

They would also have noticed other properties of acids such as the sting of formic acid in ant bites and the corrosive effect on the skin.

 

It is not known which hero cook spilled animal fat on the fire and roasted it along with wood ash and then found a soapy blob when the result had cooled.
But we think this is how middle eastern civilisations discovered soapmaking this way.
The ashes provided an alkaline substance which is breaks down fat, something most acids are unable to do.
So their for ashes passed into Arabic,  Al-Kali and then into English as alkali.
Wood (and other plant ) ashes contain what gardeners and farmers call 'potash' which makes a strong alkali with water that we now call potassium hydroxide.

So we have the origins of acids and alkalis.

The second historical period when humans were able to refine and classify substances, many of which occurred naturally or as with potash by heating or burning and perhaps then adding  water.
The addition of water was known as slaking; probably the most known and important product was slaked lime or calcium hydroxide, which formed the basis of Roman cement.
To obtain this rocks containing calcium carbonate were heated to obtain what was known a quicklime (which we know as calcium oxide). The was the slaked to produce the hydroxide.
Calcium carbonate introduces another acid  we call carbonic acid, which is important in environmental chemistry.

So during this period many names were introduced that were carried forward to the third period which is for next time.

Interestingly these time periods have have been 'telescoping'. The first was measured in thousands of years, the second in hundreds of years, and so on.

[Jack777]

14 hours ago, exchemist said:

If you go way, way back, I think they tasted them and they were sour. Your tongue can detect acid this way. 
There is a bit of the history here: https://pubsapp.acs.org/subscribe/archive/tcaw/12/i03/pdf/303chronicles.pdf

 

Thank you, that was very interesting.

5 hours ago, studiot said:

How we got to our modern view of chemistry can be divided into four broad periods.

 

Absolutely fantastic! This was exactly what I was looking for, you have no idea how much I appreciate this.

I bought some kids chemistry books as well as the two mentioned in this post. Now I can understand how things were done and can start to move on, I just needed a historical deep dive for a reference for me.

Thanks.

[studiot]

5 minutes ago, Jack777 said:

Absolutely fantastic! This was exactly what I was looking for, you have no idea how much I appreciate this.

I bought some kids chemistry books as well as the two mentioned in this post. Now I can understand how things were done and can start to move on, I just needed a historical deep dive for a reference for me.

Thanks.

Hopefully your continued exposure to chemical selected names and terms is beginning to bear fruit.

So let us carry on with unravelling the history of the subject.

The ancient Greeks thought there were four elements, Earth, Water Air and Fire and that all substances were made up from these.
In fact they used a different word and the word element came into English from the Latin elementum.
Furthermore the concept was very vague in detail and one Greek in particular (Democritus) asked the important question.

"What happens if you cut a substance in half, then in half again and in half again and so on ?"

He proposed that you would eventually reach a stage where the substance became indivisible and called this piece atomos from where we get the English word atom.

This situation continued until the late 17 hundreds when Dalton revived the twin concepts and included the new question

"If you can cut substances apart, how can you put them together ?"

In his words he described atoms as

"All atoms of the same element are alike, globular and all of the same magnitude, but atoms of different elements have different weights."

Thus moving atoms from substances to elements and making the distinction.

It should be noted that 'weights' were not measured in pounds and ounces or kilogrammes.
Hydrogen was give the weight exactly 1 unit and other elements were measured as multiples (including decimal fractions) of this.
These weights were called atomic weights.

This was a great step forward but it did not explain how or why atoms could be combined in 'fixed proportions' to form substances they could split up.

Atoms could not be split up i.e. were indivisible.

These insights plus the growing list of elements enabled the first versions of the periodic table to be drawn up.

But they were wrong because they placed elements in order of increasing atomic weight, which led to inconsistencies in the chemical properties compared to their placement in 'the table'. 
The table is called periodic because these properties occur at regular spacing when the elements are placed in the proper order.

They had not yet addressed the second question "How can you put them togerther?"

Then in 1869 Hofmann, then working in england, coined the English word 'quantivalence'.

He introduced the concept of Valency or the combining power of atoms and your next equation from chemical mathematics.

Atomic weight  = Equivalent weight x Valency.

This ushered in the third era in the History of Chemistry and led to a new idea  - that of the molecule.

At that stage, they still though atoms were 'indivisible' they did not know about electrons, protons and neutrons  -  that comes in the fourth period up to the present day and was largely invetigated by Physicists.

So they quickly determined that oxygen has 2 'hooks' , carbon has 4 'hooks' and nitrogen has '3 hooks' and hydrogen has 1 hook.

These hooks were also quickly translated into the ubiquitous chemical stick diagrams we still use today.

Here is the diagram for 'ethane' where you can quickly see that each carbon is linked by 4 sticks or hooks and each hydrogen is linked by 1 stickk or hook.

 

This is the 'molecule' of pure ethane.

 

 

 

 

[Jack777]

9 hours ago, studiot said:

So they quickly determined that oxygen has 2 'hooks' , carbon has 4 'hooks' and nitrogen has '3 hooks' and hydrogen has 1 hook.

 

Thank you, this is a great explanation. But what are these hooks? How do they know they have hooks?

[studiot]

Just now, Jack777 said:

Thank you, this is a great explanation. But what are these hooks? How do they know they have hooks?

Who are 'they' ?

We try to be more specific in Science.

But this story is a good example of how Science works.

Science does not work on proof.
It works by using the best explanations available for known observations.
If new observations become available that show different results then a scientist has choices.

He can propose a new explanation that explains both the old and the new.
He can propose that the new observations are the result of different circumstance or different mechanisms and thus require a new hypothesis.
He can propose new observatins to test his new theory or hypothesis.

Either way Science moves on, improving on the original and waiting for the next new set of different observations.

In fact this third period yielded thousands of new compounds all obeying the valency rules I outlined.

Ethane is a good example of this as it is a member of what is known as a homologous series of gases , called the alkanes.

 

 

 

But what they did not know before 1900 was why the valency rules are as they are.

The answer to this will come in the fourth period after the structure of the atom was discovered and is a subject for tomorrow.

Suffice to say for now that these hooks are now called chemical bonds.

 

Finally my apologies to anyone reading this, in my last post i got the date of quantivalence wrong. It should be 1865, not 1869.

The first English use of valence was in 1869.

Edited Wednesday at 10:42 PM by studiot

[Jack777]

15 hours ago, studiot said:

Who are 'they' ?

We try to be more specific in Science.

 

Sorry. I meant the people back back then who used the terms hooks.

How did they determine if something was bonded?

This set of formulas above is quite complicated to me. It's difficult to visualize. I'm sure in time I'll get there.

Thanks again.