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Flat Earth Academy- Science

Chemistry Homepage

This is a work in progress... please bear with me, come back and watch it grow? Send constructive suggestions?

What you see below might be seen as an outline for what will eventually be spread across multiple pages.

To split some material off into a chapter called "Chemistry" is misleading... but necessary.

When a plant turns water and carbon dioxide into sugar and oxygen, is that chemistry or biology?

Try to remember that while we may study things in "separate" disciplines, The Real World is an integrated entity.

Chemistry may be thought of as the study of substances.

"Substances" may be divided up many ways. For instance, we could group them as solids, liquids and gases. That rather obvious, and easy to manage system is not, sadly, particularly useful. Take water. Which is it? That depends on the temperature, doesn't it?

Imagine you have a jar of "something" in your hand. A more useful breaking up starts with asking whether what's in the jar is pure, or a mixture. And we will be using those two words in a very precise way.

Sadly, our "precise way" is defined somewhat tautologically, in other words, with a definition that somewhat goes around in circles. But, I hope, you will soon get the hang of it.

Pure.... in the sense chemists use the term:

Mixtures... in the sense chemists use the term:

When you have a jar of a pure substance, it is a jar with just one chemical in it.

Trick question: In what way is every example of a "pure" substance faulty?

Answer: Each of those jars will also contain some air, won't they? But, apart from the air also in the jar, the examples of "pure" substances are good.
(All of them except one, actually. Thank you to the reader who wrote and pointed this out to me! Which one? (Answer appears a little way down the page. Think first, then read on.))

What do we mean by "one chemical"?

If you had a "super" microscope, you could see that water, sugar, oxygen, gold are all made up of extremely small particles. And, for each of those things, the particles in a jar of water, a jar of sugar, etc, are all the same. (Different particles for, say, water and sugar.... but in a jar of just one or the other, all the particles are the same.

Think for a moment about the mixture examples. What sort of particles do you think you would find in the jar of mixed (hence the word "mixture", of course) sugar and salt? Yes! Salt particles and sugar particles! Even without the "super microscope" you would be able to tell the macroscopic "bits" of salt and sugar apart. Go look at some. You'll see. The white powders are not quite the same, are they?

When we get to the salt water, things become tricky. The water and the salt have mixed so thoroughly that you can no longer see that there is more than one substance in the jar. But if you started with water and added salt, your tongue could tell you that the salt... hardly changed... was still there. You could also separate them out again, and get the pure water, pure salt back into two separate jars.

Generally speaking, using your tongue for tests in a chemistry lab is a Bad Idea. But the good news in the previous paragraph is that there is a whole world of fun to be had in devising ways to separate pure substances out of mixtures.... a story for another time.

But we don't have the "super microscope"

So... a pure sample is one that contains only particles of one kind. Salt. Water. Oxygen.

But how do we "look at" the substance, to see the particles? We can't. For now, the easiest thing is just to learn what things are "pure", in the chemist's sense, and what aren't. But don't despair! When you've learned more, you will begin to see how you can know, without having to rely on what others tell you, what are the pure substances, what are mixtures.

A little thing to be aware of: "Particles", as used above, is not being used in a special, "chemist's" way. And there are all sorts of "particles" we will meet in chemistry and physics. The word will be used several different ways. Don't worry too much about this, we are going to replace "particles", as used above, with two better words, and then we can stop using "particles", which is a word like "thing"; it is ambiguous. (Bad!)

"Pure" honey is a mixture?? What's going on??

Why is "pure" honey listed as a mixture?

The people selling the honey are not lying (we hope!) The jar may indeed contain honey, and nothing but honey. However, if you were to look at it with the "super microscope", you would find water "particles", sugar "particles", bits of pollen and spores, "particles" of chemicals which give different honeys different flavors.

According to Wikipedia, a typical honey will consist of about 17% water, 78% sugars, leaving about 5% for other stuff.

A detail: Notice I said "sugars"? In chemistry, "sugar" is a term for a whole group of chemicals. The sugar we normally have in a bowl in the kitchen is called sucrose, and that is only one of the sugars in honey... only about 2% of the honey, in fact. (The main sugar in honey is "fructose". It looks and tastes much like sucrose... but if you could look at the particles of each, you would find they aren't the same.)

So... that's why "pure" honey is a mixture, as far as a chemist is concerned. You can become knowledgeable about what's pure, what's a mixture... to a chemist... with just a little work. And before long, you will know a few other things which will give you a way to tell.

(The jar with no air was the one full of oxygen, by the way. Air and oxygen are not the same thing. Air is a mixture of, mostly, nitrogen and oxygen.)

But first....

Is EVERYTHING "pure" or "mixed"?

Yes and no.

If you mean "everything" in a sensible way, yes.

But happiness, light, history, anger are neither "pure" nor "mixed", at least not in the way chemists use the words.

(Pretty well) every substance or object is pure or mixed. This includes gasses, too. Don't forget them, just 'cause they're "invisible". (Not all are, actually, and all of them would bubble if blown through water, wouldn't they? Invisible? Maybe not, when you think about it.)

Time to divide things again

What are mixtures made of? Pure substances!

In theory... it isn't always so easy in practice... any mixture can be separated out into the pure substances it is made up of.

As I said earlier, the different tricks people have thought of over the years for separating the components of mixtures is a whole topic from which many people have derived a lot of fun over the years.

Suppose you had a mixture of peanuts and pennies? How to separate? Your fingers, of course. Peanuts and iron nails? You could use your fingers again, but a magnet would be a more clever answer. Salt and water.... and you want the salt. You'll never do that with your fingers. And if you want the water things get tricky. But to get the salt: Put the salt water in a glass, leave it on a warm shelf, come back in a day or so, and you'll find that the water has left, by evaporation, leaving you with pure salt. And so on.

Now.... think just about hundreds of jars of "pure" (just one sort of particle) substances....

The two sorts of pure substance

All pure substances are either elements or compounds.

For now, the easy thing for you to do is to learn the list of things that are elements. All the rest are compounds.

Rather dull.... but it is just a start.

Who cares? Not you, at this stage. But if you don't make the effort, it will be harder to get to the stage where things have become interesting for many, many people who have trod this road before you. The people who didn't give up, and didn't miss out on the fun to be had... later.

I will give you a better way to tell elements from compounds.... later.

You will know many important elements... although what you think of when you hear their name may be something that isn't really that element. In the following list, I've given you the chemist's name for each element first. When there's something in brackets after the name, like in the first case, carbon, what's in the brackets is something you are likely to know, which is at least mostly made of that element.

Those are some of the "everyday" elements which I would guess you might be familiar with.

(There's actually a lot more to say about carbon... it is a rather "fancy" element... but that's for another time. For now, yes, diamond and pencil lead are also carbon... with the particles stuck to one another differently than they are stuck together in coal. Elements are usually found in just one form (at a particular temperature).)

There are a bunch of other metals which are elements. Before I list them, let me explain what I meant when I said that the gold in jewelry is "mixed with other things".

Suppose you took some candle wax, melted it, mixed in some coloring agent, and let it freeze again. Even if the candle wax was originally an element (which it isn't), the now colored, solid, candle wax is clearly (I hope) a mixture. When we mix peanuts and pennies, it is obvious that we have a mixture. When we mix salt and water, it isn't as obvious, but I hope you still "see" that there are two sorts of particle in the jar. When we mix two things while they are melted, and then let the mixture freeze into a solid, be it colored candle wax, or jewelry gold, it is a little harder to "see" that we are still dealing with a mixture... but you can do it, can't you? We're going to look harder at this "how can we tell" later. (Jewelry gold has things like copper, silver, and a little zinc mixed in with the gold. The result is a harder metal, which lasts better than the soft pure gold.)

Part of the answer to "how can we tell if we have a jar of a pure element?" is that there is only a short list of elements. If what we have in the jar isn't one of them, then we either have a mixture in the jar, or the other thing that you can have when there's only one sort of particle in the jar, that "other thing" being a compound. Salt is a compound, and we will come back to the compounds when we've finished with the elements.

So! Here are some other metal elements you've probably met. You may even have met them as nearly pure examples of the element...

Metals you probably haven't "met", but have probably heard of...

That last one is really cool. It is a pity that you will probably never get a chance to play with it. Have a search around YouTube for videos of mercury. It is a metal, but it is also a liquid at room temperature. The other element which is a liquid at room temperatures (and pressures) is the non-metal bromine (brown liquid, evaporates easily into red gas. Name comes from "stench of he-goats"! (Thank you Wikipedia.)

Also cool, and also locked away out or your reach is sodium. It is stored in oil, because as soon as the air gets to it it begins to "rust". If you scrape away the "rust", you will see that sodium is silvery, just like silver (!) and many other metals. Drop a small piece in water, and stand back! They react violently. Again.. go on a YouTube hunt. Another thing that is cool about sodium is that it is very soft.... more like a hard cheese than the everyday metals, although it doesn't crumble the way cheese will.

Time for a little digression, sorry. You will hear people talk about things like "We don't want too much sodium in our diet", or "potassium is good for making plants grow". When people speak like this, they are using a shorthand. No one has sodium in their diet. They have compounds of sodium in their diets. (We'll be coming back to "compounds".)

There are some metals which are not elements. They are frozen mixtures of elements, like the jeweler's gold, and the colored candle wax. Three important examples...

There are a bunch of gas elements which are mostly rather boring to look at. They look like air, except as noted...

That pretty much does it for the "main" elements. There's just the following three non-metal, solid elements you should also be, or become, familiar with....

There are 94 naturally occurring elements, so when you know a bit about the ones above, you've made a very good start. The "un-natural" elements are things made in university physics labs, there aren't very many, and they don't last very long when they are made, and you don't need to worry about them for a while yet. Probably not until after you finish your Flat Earth Academy studies, in fact.

How do we know we've found them all? That's a story for another day... but a Good Question! Happily, there is an answer... and we do know!

Whew! Take a break!

I hope you don't think that I ever said that completing the study possible at the Flat Earth Academy would be easy? But if you really read and digested the material above on "the elements", then Congratulations! You have made a huge start on with a big topic which will help you understand what you see in the world around you better than most people, for the rest of your days. Take a break. After your break, we are going to deal with....

All the other pure substances

Earlier, we looked at the world, and narrowed our view down to "substances". We then split them into mixtures and pure substances. Of all the pure substances, using the term as a chemist does, about 94 are "elements", which we have just made a major start on, and The Rest are compounds.

The amazing... if somewhat confusing... thing is: All the compounds are made from just the 94 elements.

BUT ! .....

Even though water is "made from" hydrogen and oxygen, it is not a mere mixture of those two elements.

Let's back up a bit and look at the elements hydrogen and oxygen before we talk about the compound made with those elements.

Hydrogen: Looks like air, but....

If you fill a balloon with hydrogen, the balloon will float in air.

If you take a sliver of wood, light it, and you put that burning splint into a test-tube filled with hydrogen, you will usually get a dramatic "pop" as the hydrogen, mixing with air from the room, burns rather rapidly.

Oxygen: Looks like air, but....

If you take a sliver of wood, light it, blow it out so that there is no longer a flame, but a glowing ember remains, and you put that glowing splint into a test-tube filled with oxygen, the splint will usually burst into flame again.

If you direct a gentle "breeze" of pure oxygen onto a glowing cigarette, it will burst into flames and burn rapidly, almost as if you'd added some combustible liquid and lit it. Seek on YouTube... I hope you will find. (... Good videos!)

So. That's hydrogen and oxygen.

If you were to mix them together, a jar full of the mixture would look like air. Mixing them together would be a Bad Idea, because the mixture is explosive, and can be set off very, very easily. But if you mixed them together, the result would look like air.

But a little while ago, I said that water is "made from" hydrogen and oxygen. And so it is. It doesn't look like air. It doesn't burn. It doesn't explode.

The "secret" is that the hydrogen and oxygen have combined. You no longer have hydrogen and oxygen "particles". You have a bunch of new particles. In each particle, there are two hydrogen atoms and one oxygen atom. Such particles... particles made up of several atoms... are called molecules. A container full of just water molecules will be a container of "pure" water... just one sort of particle present. The fact that those molecules were made from hydrogen and oxygen atoms is sort of "hidden". The "hydrogen-ness" of the hydrogen atoms, and the "oxygen-ness" of the oxygen atoms is lost when the atoms join up to make the water molecules.

This secret takes a bit of getting used to. You won't "understand" it all at once.

Jars with pure elements in them: The "particles" are atoms of the element. (Or sometimes two or more atoms of the same sort joined together. When this is the case, the properties we know for the element are the properties of these particles.) And remember the good news: If all else fails, you can tell if "x" is an element just by checking the (fairly short) list of all the known elements.

Jars with pure compounds in them: The "particles" are made up of atoms of two or more elements, but the properties of the compound are almost unrelated to the properties of the elements making up the compound.

Jars with mixtures in them, e.g....

.... will have more than one sort of "particle" present. If you can find a way to separate out the particles, you will end up with two jars, each holding a pure substance, with that substance's properties. The properties of the substances in the mixture remain, even when the substances are mixed.... look closely at the gold dust+ sugar: You will see tiny yellow bits, and tiny white bits. Of course, sometimes the mixing is so thorough that it becomes difficult to see the properties remain unchanged... take salt in water, for instance. You won't see the individual grains of salt, will you?

There's another thing that distinguishes mixtures and compounds. When you mix gold dust and sugar, you can use a little of one and a lot of the other... or mix them 50:50... or 20:80, etc.

When you combine hydrogen and oxygen, and thus make water you will always use exactly two parts of hydrogen to every one part of oxygen. (The combining can be done, but must be done carefully, to avoid the explosion which can result if too much of the elements combine at the same time.)

(By the way... have you spotted two similar words which keep cropping up? "Combine" and "compound" relate to the same concept.)

Furthermore, if you can make water by combining (not merely mixing) hydrogen and oxygen, you can also, in theory, make hydrogen and oxygen from water. And if you find the way, you will get back two parts hydrogen for each part of oxygen you get. Magic! (Well, not really... but it seems like it!)

More compounds....

The list of compounds is vast... basically it is the number of pure substances minus 94. (You do see why, don't you? Think about it, ask about it, until you do!)

Here are some everyday examples of compounds, in addition to the salt, water and sugar we've seen so far....

That's just a tiny random sample.

Are there "pure" substances which are not elements, not compounds?

Not as far as a chemist is concerned, no. But in everyday speech we have names for things, like the honey we discussed before, which are actually mixtures, and not "pure" in the chemist's sense of the word.

Examples: vinegar, wine, gunpowder.

They aren't elements. They aren't compounds.

Don't despair! The "trick" is that a chemist wouldn't be inclined to give such things a name, as if it were "one thing". No big deal. Do you really want to say "Pass me the mixture of water, acetic acid, and flavorings" when you want some vinegar for your fish and chips?

Wine is a mixture of water, ethanol, colorings and flavorings. Gunpowder is a mixture of carbon, sulphur and sodium nitrate.

All of the things I've listed as the constituents of the mixtures with a one-word everyday name are specific elements or compounds... except the "flavorings" and "colorings".... which are names for groups of compounds.

Here are some more everyday simple mixtures with one-word everyday names....

So... is that every "thing"? Not quite, if you want to be fussy. The mixtures we've covered so far can be put together fairly approximately. Wine, for instance can be strong (high alcohol content) or weak (less alcohol).

There are "things" which are only "themselves" when the different materials mixed together are organized in a particular way. One of the most complex things you'll ever encounter is of particular interest: human beings! They are "just" complex "mixtures" (put together in a very particular way) of sundry elements and compounds. (A large part, roughly 65%, of every human is mere water. Just think... if you weight 50kg (c.100lbs), then only about 22kg (c. 45lbs) of you is anything but water!)

For a simpler example, take paper. It is usually mostly cellulose, but it needs the cellulose to be in fibres, the fibres have to be felted together properly, and sometimes there is a coating of a very fine clay. Wood is also full of cellulose. It has other things, too... but while an oak table and a balsa wood table are made from almost the same things, you wouldn't confuse one with the other would you? Or either for paper, and it is more than just the "other things" that make wood and paper different. How the ingredients of the mixture are mixed matters.

Cookies and bread are made of mostly the same things... but they are different, because of how the things are mixed.

Even something as "simple" as Scotch tape is more complex that it seems. Not only is there the obvious "sticky" layer, and the "strong" "tape" part, but there's at least one more, sometimes two more, other layers. (They ensure that when you pull some tape off of the roll all of the "sticky stuff" stays on the right side of the "tape" part.)

But! If you have learned that....

Substances are "pure" or "mixed".... and

.... Pure substances are "elements" or "compounds"...

... and you really grasp what all those mean....

... then you've made a great start to studying chemistry!

The next stage of your journey into chemistry is looking at individual elements and compounds, getting to know them better. You will also look at the "magic" of elements combining into compounds, and the reverse process, the decomposition of compounds into elements.

And then you will be a great chemist! And even if you don't want to be a great chemist, things you see in the world around you will make sense in a way that most people are blind to. And if you want to study, say, biology, things you need to know to fully enjoy those other subjects will already be understood by you, because of the work you've done here.

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