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Molecular picture of matter
Beginner
All matter is made of moving particles.
All matter is made of atoms and molecules in constant motion with forces between them. Solids have particles vibrating in fixed positions, liquids move past each other, gases fly freely. This picture explains pressure, temperature and diffusion from mechanics.
A drop of ink spreads in water without stirring.
Atoms aren't static.
In more detail
Matter is made of atoms and molecules in constant motion, and the arrangement and motion of these particles explain the properties of solids, liquids and gases.
Real-world uses
- Materials scientists explain strength and melting points using atomic arrangements.
- Chemists predict reaction rates by modelling molecular motion.
- Chemists explain why a gas expands to fill its container and why a solid holds its shape, using the motion and spacing of its particles.
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Frequently asked questions
Are atoms really moving in solids?
Yes, they vibrate about fixed positions, even at room temperature.
Why is kinetic theory useful?
It explains macroscopic properties from microscopic behaviour.
Are atoms really moving in a solid?
Yes. Atoms in a solid vibrate around fixed positions, which is why solids still have thermal energy.
Related topics in Kinetic Theory & Statistical Physics
Brownian motion · Ideal gas assumptions · Pressure from molecular collisions