How particles behave

~ a tug-of-war between two forces ~

Alberta Grade 6 Science
Organizing IdeaMatter — Understandings of the physical world are deepened by investigating matter and energy.
Guiding QuestionHow can the particles of matter be influenced by heating or cooling?
Learning OutcomeStudents investigate how particles of matter behave when heated or cooled and analyze effects on solids, liquids, and gases.
This lesson covers: How particles change speed and distance from each other when heated or cooled; the tug-of-war between particle motion and attractive forces; how the balance of those two forces determines whether a substance is a solid, liquid, or gas.
click in
the chamber!
1

Particles pull on each other

Particles have a tiny invisible pulling force between them. Think of it like a weak magnet inside each one. When you put particles together, they travel toward each other and settle into a tight pattern.

↓ tap anywhere on this card to add a particle ↓
particles in the chamber: 2
2

Particles are also constantly moving

Every particle in matter is constantly moving — vibrating, sliding, or flying around. We call the energy of that motion kinetic energy. The faster a particle moves, the more kinetic energy it has. The hotter something is, the more its particles move.

↓ click anywhere to add a flame and warm the particles ↓
cool
hot
notice something?
The particles never fully stop moving — even when the chamber cools back down, they keep drifting at a baseline pace. That's because particles always have some kinetic energy. When you add a flame, they get extra energy and zoom faster, but they soon share it with their surroundings and settle back to the chilly baseline.

That constant motion is one half of a tug-of-war.

click in
the chamber!
3

It's a tug-of-war

The pull tries to hold particles together.
Their speed tries to fling them apart.
Add particles, then change the temperature — see what wins.

↓ click anywhere on this card to add a particle ↓
cool hot
the PULL is winning → particles bond together (solid)
4

An everyday example

two friends holding hands

Imagine two friends holding hands. If they walk slowly side by side, their grip is strong enough to keep them together. But if they start running wildly in different directions, their hands slip apart — their motion is too strong for the grip to hold.

two magnets joined by a spring

Now imagine two magnets joined by a stretchy spring. Hold them still and the spring keeps them close. Shake them gently and they wobble but stay together. Shake them really hard and the spring stretches until they fly apart.

So why does cold pull particles together?

Because cold particles move slowly, the pulling force easily wins the tug-of-war. The particles get pulled close and stay there.

When you heat them up, they move faster and faster, until eventually they win and break free.

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