Notes

Kinetic Particle Theory

If you’re thinking this topic sounds familiar to you, you’re absolutely right. Everyone remembers their first Chemistry topic – sitting there in class wondering what the heck is going on. Well you’re in luck, we’re here to unpack these three cheem words and help you understand this fundamental concept in Chemistry!


1. It’s more important than you think.

The kinetic particle theory is used to explain matter. And matter is basically, well everything around us. This is why we learn about this theory before anything else in Chemistry. Don’t worry, it’s a lot simpler than it sounds.

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The Kinetic Particle Theory

All matter is made up of many small particles that are constantly in a state of random motion.

2. The small but mighty particle.

Just like your favourite iPhone is made up of many components, all matter is made up of extremely small components called particles. So, in theory, your iPhone actually would look something like this.

An iPhone, just like all matter, is made up of millions of particles (pictured in the orange zoom-in box above).

Within the matter itself, these particles are in constant and random motion. This is where the kinetic part comes in. While the matter itself (i.e. your phone) isn’t moving, the particles within it are having a killer party inside there!

3. Some parties rock, others not so much…

Depending on the state of the matter itself, particles move to different degrees. This is dependent on two main factors: the amount of energy each particle has, and the attractive forces between each particles.

StateSolidLiquidGas
Arrangement of particles
Very closely packed, and arranged in an orderly manner.

Closely packed and in a disorderly arrangement.

Far apart and disorderly arranged.
Attractive forces between particlesVery strong.Strong.Very weak.
Kinetic energy of particlesVery low.Low.High.
Particle MotionVibrate and rotate about fixed positions.Move freely by sliding over each other.Move randomly and freely in all direction at high speeds.
The states of matter in a nutshell – we look at the properties of the particles within.

4. The big difference – what makes gas, gas.

Because of these differences between properties of the particles, different states of matter have different properties that define them. It comes down to two main properties – shape and volume.

Since particles are so close to each other in solids and liquids, they occupy a fixed volume. A gas, however, can be compressed as particles can afford to move closer together and fill up the empty spaces betwee them – gases don’t have fixed volumes.

Particles of gases and liquids can move freely. When they are placed in containers of various shapes, the particles move into and fill the space of the container. This leads to liquids and gases not having a fixed shape. Particles in solids, on the other hand, are in fixed positions so they stay where they are. Solids therefore have fixed shapes.

Although, I can think of an exception to this statement…

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