Answer:
Atomic theory is the scientific theory that matter is composed of particles called atoms.
Solids: their molecules are close to each other.They can't change their shape nor they can does it expand to fill the entire available volume like gas.
Liquid: A liquid is an incompressible fluid that conforms to the shape of the container in which it is stored. It's molecules are not too close to each other.
Gas: Most gases cannot be seen but are present in the atmosphere.Their particles are far from each other.Gas is described by pressure, volume, temperature and number of particles
Explanation:
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