Published: 28 May, 2020 | Last modified: 30 Nov, 2021


In the last post we learnt about matter and we understand matter is anything that has mass, occupies volume in space, and exists in different states. But have you wondered what is matter really made of?

If you have ever tried to use a magnifier on your laptop's screen, you may have noticed the little colored dots like the one shown below.


Photo by Umberto on Unsplash

What if you further zoom in to the little dots, and zoom in and zoom in and zoom in... what will we see at last?

Well, the answer is: atoms.

Atom is one of the particles that make up of matters. Other types of particles include molecules, which is made when more than one atoms come together and undergo some chemical changes. Atoms and molecules does not have charge, or maybe we should say that they have zero net charge but may have charges on one side while having opposite charges in the other side.

There're also charged particles, namely anions which have net negative charges, and cations with positive charges. You can think of anions as negatively charged atoms or molecules, while cations as positively charged atoms or molecules.

Each particle is so small that you can't really see it, eg. atoms are about the size a million times smaller than the thickness of human hair, but you do see an ice cube, or a glass of water. Why is that?

The reason is that matters are made of billions and billions and billions of particles. You may not believe it, but a cup of 50mL water may actually contain 1,800,000,000,000,000,000,000,000 or 1.8 septillion water molecules. What's more, each water molecule contains 3 atoms, that gives 5.4 septillion atoms in that small cup of water.

Particles Charge Composition
Atoms Neutral -
Molecules Neutral More than one atoms
Anions Negative Negatively charged atoms or molecules
Cations Positive Positively charged atoms or molecules

Particles summary

Particles in matters

So how do particles make up matters? We'll look into matters at different states individually.


In solids, all the particles are packed together with a certain pattern. All particles are touching each other just like what you'll do to the books on the bookshelf. Particles must stay where they are and they are not able to move around, that's why solids have defined shapes and volumes. However, particles do vibrate a little bit around their fixed positions.


As for liquids, we know they can flow. This is because the particles in liquids are able to move as they're not so closely packed together. However they do touch each other still. So when the particles move, liquid flows. Liquids have no fixed shape, but they do have fix volumes. No matter how the liquid particles move, they always touch each other, hence they will not occupy more space.


For gases, it is a different story. Gas particles are pretty independent. They do not touch each other, they do not interfere each other, and they will move all over the space. As a result, gases have no defined volume nor shape. They simply occupy whatever space available in the container.

Chemical changes

Now let's revisit our question about physical and chemical changes. To understand this, we could make a simple metaphor. In a cup of water, there are a lot of water molecules stacking on each other. Just imagine it as a few pieces of paper in a bag. During a physical change, these papers would be separated by a larger distance, or brought together, or even crunched. However, they will not be torn apart. In terms of water molecules, these molecules could be going far away from each other, or compressed firmly against each other, but they stay as water molecules during physical changes.

During chemical changes on the other hand, water molecules would be broken into atoms, just like tearing a piece of paper apart. The atoms would recombine to form other types of particles, but not water molecules any more. Therefore, after a chemical change, water is gone.

Atoms, which only recombine during chemical reactions and will not be broken, serve as the smallest unit during chemical changes. The main fundamental difference between physical and chemical changes is whether molecules would be broken and atoms would recombine to form other kinds of molecules. Now you get it?

Next, we'll learn what's inside atoms and how atoms could come together giving rise to matters.

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Subatomic particles make up atoms. There're different types of subatomic particles, and they have different properties

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