States of Matter

The Particle Model is used to explain the different states of matter and the unique properties of each state. It represents each particle as a small, solid sphere which can be an atom, molecule, or ion, depending on the substance.

The three states of matter are solid, liquid and gas.

Water is a great example of the three states of matter.

  • It can exist as a liquid, such as when it is poured into a glass
  • It can exist as a solid, such as when it freezes into ice
  • It can exist as a gas, such as when it turns into water vapour
An illustrative diagram showing the three states of matter: a stack of ice cubes labelled 'SOLID' with a close-up view of its molecular structure, a laboratory flask emitting vapour labelled 'GAS' with a depiction of its dispersed molecular arrangement, and a beaker filled with liquid labelled 'LIQUID' showcasing its closely packed molecular formation.

Individual particles do not have the same properties as the bulk matter. When a large number of particles come together, the substance formed will have different properties, due to the interactions between the particles.

For example, isolated water molecules have individual movements and energies. However, when many water molecules come together they form a large body of liquid water. The properties of the water as a whole, such as its ability to flow, will be different to the properties of an individual water molecule.

Solids

Solids are one of the three states of matter, which have a rigid shape and a resistance to changing shape. The image below represents the arrangement of particles in a solid.

Illustration of a solid state of matter contained within a rectangular vessel. The vessel holds closely packed blue spheres representing particles in a solid. The word "Solid" is written at the bottom.

In solids, the particles are tightly packed together and held in place by strong forces of attraction. This results in a regular arrangement of particles and limited movement of the particles. The particles in a solid vibrate about a fixed position, but they cannot flow because they are closely packed and unable to move past one another.

Compared to liquids and gases, solid particles have less energy, which makes them more stable. They also cannot be compressed because the particles are already very close together, with little room for movement.

Liquids

Liquids are a state of matter with the ability to flow and take the shape of their container. The image below shows the arrangement of particles in a liquid.

A representation of a liquid state inside a container. The container is filled with loosely arranged blue spheres, signifying liquid molecules. The word "Liquid" is written at the bottom.

In liquids, the particles are held together by weaker forces of attraction than in solids, which allows them to move around each other. This results in a random arrangement of particles and a fluid form that adapts to the shape of its container.

Compared to solids, liquid particles have more energy, allowing them to move freely, but less energy than gas particles. This balance of energy gives liquids their characteristic ability to flow.

Like solids, liquids cannot be compressed because the particles are already closely packed, leaving little room for movement.

Gases

Gases are a state of matter that lacks a definite shape and can fill any container.

A diagram illustrating gas molecules, depicted as scattered blue spheres, within a transparent container with the label "Gas" at the bottom.

In gases, there are no forces of attraction between the particles, so they move freely in all directions. This results in a random, spaced-out arrangement of gas particles and a lack of definite shape.

Gas particles have more energy than those in solids and liquids. This contributes to their ability to spread out and fill the space of a container. They can be compressed easily because there is more free space between particles.

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