# Kinetic Particle Theory

## Kinetic Particle Theory

Air consists of tiny particles that are in a constant random motion. Mostly, all of us have seen this working in our daily life but very few would have observed the dancing particles we see in light beam mostly from projectors. As air particles are too tiny for our to see, we look at the dust particles that are moving because air particles constantly hitting the dust particles.

The explanation provided for the ‘dancing’ particles is truly based on kinetic particle theory. To define kinetic particle theory we would say:

[quote arrow=”yes”]All matter is made of tiny particles that are in constant. random motion.[/quote]

1. Matter
2. States of Matter
3. Change of states

## What is Matter?

Everything around us is made of matter. Living things including you, your pets and Non Living things such as your chair, your books and dust is made of matter as well. Matter has no well-defined state and can exist in different states. The three common states that the GCSE / IGCSE & GCE O Level students would be studying are Solid, Liquid and Gases. There are substances that have the ability to exist in all of the states. The substance that you are thinking is Water, which is absolutely correct.

## States Of Matter

### Solids

Properties Solid Properties Why they are like this?
Particles Arrangement Very closely packed They are regularly arranged in lattice.
Movement of Particles Vibrate in a fixed position Particles cannot move freely due to the strong forces of attraction that provides enough kinetic energy to rotate around fixed positions and vibrate.
Inter-molecular Forces Extremely strong They have extremely strong force of attraction because of (Ionic/Covalent) strong bonds made between the particles.
Inter-molecular Spaces Negligible The bonds made are so close and tight that negligible space is left in between.
Shape Fixed shape Solids have a very high force of attraction that makes them remain in a fixed shape.
Compressibility Uncompressible Particles are very close to one an-other.
Volume Fixed As solids are uncompressible they have a fixed volume.
Diffusion Cannot diffuse For diffusion particles need to move freely: whereas, solids cannot.

### Liquids

Properties Liquids Properties Why they are like this?
Particles Arrangement Irregularly Arranged Particles have low forces of attraction, which allows particles to move in a disorderly manner.
Movement of Particles Slide Over Each Other Particles haveĀ  more kinetic energy than solids that allows the particles to slide over each other.
Inter-molecular Forces Strong They have weaker force of attraction compared to solids.
Inter-molecular Spaces Tiny Spaces The particles are touching each other but gaps are present also.
Shape No Fixed shape

Container Dependent

Particles have the ability to move around each other.
Compressibility Almost uncompressible Although Particles are far away from one another, the particles are still packed closely together.
Volume Fixed Although Particles are far away from one another, the particles are still packed closely together.
Diffusion Slowly Diffuses For diffusion particles need to move freely: whereas, Liquids do diffuse but slowly because particles don’t move as freely as gases.

### Gases

Properties Gases Properties Why they are like this?
Particles Arrangement Very Far They have no arrangement.
Movement of Particles Move Freely in any direction Particles move freely in any direction due to the very weak forces of attraction.
Inter-molecular Forces Weak They have extremely weak force of attraction.
Inter-molecular Spaces Large Particles are far away from each other because of very weak forces of attraction between them.
Shape No Fixed shape Solids have a very high kinetic energy that makes gases to move rapidly and have no definite shape.
Compressibility Compressible Particles have large spaces in between them that allows them to get compressed.
Volume Not Fixed As gases are compressible they don’t have a fixed volume.
Diffusion Quickly Diffuses For diffusion particles need to move freely and gases move about rapidly.

## Changes Of State

### Why Substances Change State?

As particles of matter are in constant motion that means they have kinetic energy as well. Solids have the least kinetic energy; whereas, solids have the most. While a substance changes its state, heat is given out or taken in, it is simply heated or cooled. Following are the common changes of states.

Basic principles / processes involved in heating / increasing temperature?

Heat energy absorbed by solid/liquid is converted to kinetic energy that causes vibration in particles about their fixed positions. After the temperature gets too high/enough for the particles present in the substance, the vibrating particles gain enough energy to overcome the forces of attraction that keeps them bonded together. As a result particles begin to move away, and after a certain time the particles are no longer in their fixed positions. The substance has changed its state e.g in melting from solid to liquid, and in boiling from liquid to gas.

Basic principles / processes involved in cooling / decreasing temperature?

Heat energy released causes solid/liquid to lose kinetic energy. After the temperature gets too low/enough, the particles lose enough energy to move freely. As a result particles begin to move closer, and after a certain time the particles get in their fixed positions. The substance has changed its state e.g in freezing from liquid to solid, and in condensation from gas to liquid.

## Heating/Cooling curve for water

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