The Particulate Nature of Matter

The particulate nature of matter

The states of matter

Matter is anything that occupies space and has mass

Solids

Solids have a definite volume, a definite shape, and are incompressible. Particles* are arranged in a regular lattice and vibrate about their mean positions. There is not much separation between the particles.

Liquids

Liquids have a definite volume, take the shape of the container, and are fairly incompressible. Particles can slide past each other, and there's a bit of separation among the particles.

Gases

Gases don't have a definite volume or shape and are easily compressible. Their particles move fast in random motion and there's a lot of space among them.

Changes in states of matter

Explaining changes in states of matter using the Kinetic theory.

When we heat the particles, they gain energy. This helps them to gain more kinetic energy and overcome the intermolecular force of attraction. This causes the entire structure of the matter to fall apart and thus the matter changes state.

Pressure & Temperature of a gas

Temperature is the average kinetic energy of all the particles in a matter.

The collision of the fast-moving particles with the container walls create the pressure of the gas. The greater the temperature, the greater the kinetic energy and the greater the rate of collision and hence the greater the pressure.

Brownian Motion

It is the random motion of a solid particle (like a pollen or a smoke particle) suspended in a fluid caused by it being bombarded by the fast-moving particles of the fluid.

For example: If we suspend a pollen grain in air, it follows a random motion because it's being bombarded by the fast-moving particles of air. Though the air molecules are lighter, they can move the pollen grain because of their high kinetic energy.

Diffusion

It's a process by which fluids mix with each other because of their random movement. Its rate depends on the mass of the substances that are mixing; the heavier, the less the diffusion rate.

*By particles, I mean molecules, atoms or ions.