1-1 What is Matter?

Basic Ideas

If something can be called matter, you must be able to answer "yes" to the following two questions:

1. Does it have mass, if you put it on a scale?

2. Does it take up space? That is, does it have a length, width and height?

A few things that are not matter are energy, heat, electricity and light.

For example, think about a light bulb.

The bulb itself is made of matter -- a metal base, then either a plastic or glass top, depending on what type of bulb it is. But the light and heat it emits are not matter: they are types of energy, an idea which finds its way into a lot of different areas of science.

Mixtures vs. Pure Substances

We can classify matter in a bunch of different ways, as you will see. The biggest line we can draw is between pure substances and mixtures.

We will be adding to this flow chart later, when we get more into more details. Also, the details will help you better see what the difference is between a pure substance and a mixture, so if it's a little mysterious now, it will become clearer soon.

Pure Substances

If something is a pure substance, the particles that make up that pure substance are all identical to each other. What this particle is -- whether it's an atom or a molecule (two things we'll define later on) -- doesn't matter. All of these particles, whatever they are, need to be the same.

Let's say we have a block of a pure substance, sitting on a desk. Each of the particles in that block are identical, so we know it's a pure substance. (The diagrams below show a representation of tiny, microscopic particles, so it wouldn't actually look like this.)

Each "particle" here contains one red sphere and one blue sphere, and they're all the same. Here's another similar object, which is also a pure substance:

Instead of being made from red and blue spheres, here the particles are green stars. But since all the green stars are the same, this is also a pure substance.

Mixtures

In comparison, you have a mixture when the particles that make up an object are not identical. In the case of our block, here's what a model of that might look like:

As you can see, all the particles that make up this object are not identical: they are a mix of red/blue particles and green particles.

Types of Mixtures

Not all mixtures are the same, though. Here, sand was added to water, and stirred:

Here, salt was added to water, and stirred:

The sand + water mixture is a mechanical mixture. This is because you can see at least two different phases, or distinct parts, in it.

The salt + water mixture is a solution. This is because there is only one phase in it -- that is, it looks the same all the way through.

This means we can add a part to our flowchart:

Depending on the source, you might see mechanical mixtures being called heterogenous mixtures, and solutions being called homogeneous mixtures. In science, the prefix hetero- means "different" (think about the different phases of a mechanical mixture). The prefix homo- means "the same" (think about how a solution looks the same all the way through).

Types of Pure Substances

Elements

There's a special chart that maybe you have seen or heard of before: it's the Periodic Table of the Elements, and it looks like this:

We'll look at this in a lot more depth later. But, if we zoom in on part of the table (near the upper-right corner), you may see some familiar names:

Oxygen, carbon, aluminum, chlorine... you've probably seen or heard these words before. These are some common elements that make up our universe. Some things you should know about elements:

• there are about 120 known elements

• about 90 of these occur naturally, the others are made artificially

• hydrogen is the most common element in the universe

• the smallest particle of an element is called an atom

• most elements can exist as single atoms, but some can only exist as a pair of atoms

• atoms are the basic building-blocks of all matter

Let's say that a ballon was filled with the element helium. (This would float, as helium is very light.) Helium can exist as single atoms, so we could represent the ballon like this:

Now let's fill a balloon with oxygen... which is one of the elements that can only exist as a pair of atoms:

This is still called an "element," because there's only one type of atom here. Sure, they're paired up into molecules, or clumps of atoms, but there are only oxygen atoms present.

Compounds

Carbon dioxide has both carbon and oxygen in it. You may have heard of CO2 before... that's the formula for one molecule of carbon dioxide, the smallest amount of carbon dioxide you can have and still be able to call it "carbon dioxide."

There's one atom of carbon present, in the middle, and one oxygen atom is attached to each side. We will see more formulas like this later.

Let's fill that balloon again, but this time with carbon dioxide:

Here, we say that we have a compound:

• all the particles (in this case, molecules) are identical to each other

• but there's more than one element present, so we can't just call it an "element"

Now we can fill in our chart fully.

When trying to answer questions like the above, try this set of tests:

1. Can you find it on the Periodic Table? If so, it's an element.

2. Does it clearly contain two or more elements, and all the molecules are the same? If so, it's a compound.

3. If it fails both #1 and #2 above, it must be some kind of mixture. Look at it (or think about it, if there's no picture)... does it have two or more parts you can clearly see? If it does, it's a mechanical mixture.

4. If you know it's a mixture, but it only has one phase (it looks the same throughout), it's a solution.

Practice

The Basics

1. Re-draw the final flowchart above on paper. But, beside each of the boxes, write down one or two main ideas/definitions. Try using different colours.

2. Explain the difference between (a.) a compound and an element, and (b.) a mechanical mixture and a pure substance.

3. Air contains nitrogen (N2), oxygen (O2), argon (Ar), carbon dioxide (CO2), water vapour (H2O), and many other gases. Is air a mechanical mixture, a solution, an element or a compound?

Extensions

1. Brass is a substance that is made by mixing together copper and zinc. (a.) How many different elements are present? (b.) Is brass a mechanical mixture, a solution, an element or a compound? (It may be trickier than you think. Look into how brass is made, and that might help you.)

2. Using different colours and shapes than the diagrams above, draw a model of a sample of a substance that falls into each of the four categories of matter.