The particle model of matter — Science, 14–17 years
Matter may look continuous, but it is made of tiny particles whose movement and spacing help explain solids, liquids and gases.
Idea
Imagine matter as a huge crowd of tiny particles. In a solid they stay close and mainly vibrate; in a liquid they stay close but slide past one another; in a gas they spread out and move freely. Heating usually makes the particles move faster.
Why it matters
A substance can change shape or spread without becoming a new substance. The particle model gives a reason: the particles are rearranged or move differently. It also explains why gases can be compressed, while a solid block is much harder to squeeze.
Worked example
Put an ice cube on a plate and leave it in a warm room. First, its water particles vibrate more as they gain energy. Next, the fixed arrangement loosens and the particles slide past one another. The cube becomes liquid water, but the particles are still water particles.
Common trap
A reasonable mistake is to draw gas particles filling a container as if they were packed together. We see the gas filling the whole space, so that picture feels natural. In the model, the particles are spread out, and the empty space between them lets the gas be compressed.
Outside school
The model helps explain why perfume spreads through a room, why a bicycle pump gets warm, and why steam can push a turbine. Engineers and scientists use it when designing fridges, engines and containers for gases. It is a model, not a photograph of the particles.
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