Learning Objective

In this lesson we will learn how the energy, arrangement and movement of particles in solids, liquids and gases determines their different properties.

Learning Outcomes

By the end of this lesson you will be able to:

  • Describe the particle model of matter.

  • Describe the energy, arrangement and movement of particles in solids, liquids and gases.

  • Use the particle model to explain the properties of solids, liquids and gases.

 

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The Particle Model

particles

  • The particle model is a way of explaining the unique properties of solids, liquids and gases.
  • It states that their different properties are a result of the different behaviours of the particles making them up.
    We cannot actually see individual particles of matter, so the model is based on experimental evidence.
  • The particle model can be described as follows:
    • Firstly, particles are attracted to each other.
    • Secondly, particles have energy that causes them to move. This is referred to as kinetic energy.
    • The more energy particles have, the more they overcome the forces of attraction between them.
    • This in turn affects how they are arranged and how they move.
  • The energy of particles varies between solids, liquids and gases.
    Subsequently, their different arrangement and movement results in them having different properties.

 

(Image: gr8effect, Pixabay)

 

Particles in Solids

  • The particles in solids have low energy.
  • There is very strong attraction between particles.
  • Consequently, the particles are tightly packed, and held together in a fixed arrangement.
  • Although the particles are held in a rigid structure, they vibrate around a fixed point.

 
particles in a solid

Particles in solids are tightly packed, in a fixed arrangement.

(Left image: eveann, Pixabay)

 

Particles in Liquids

  • The particles in liquids have medium energy.
  • There is strong attraction between particles, but not as strong as in solids.
  • Consequently, the particles are tightly packed.
  • The particles are not held in a fixed arrangement as in solids, so are able to slide past each other.

 
particles in a liquid

Particles in liquids are closely packed, but free to move past each other.

(Left image: pxhere)

 

Particles in Gases

  • The particles in gases have high energy.
  • There is negligible (almost zero) attraction between particles.
  • Consequently, the particles are very far apart from each other.
  • The particles are free to move independently in all directions.

 
particles in a gas

Particles in gases are spaced far apart and free to move in all directions.

(Left image: Free-Photos, Pixabay)

 

How the Particle Model Explains the Properties of Solids, Liquids and Gases

  • Now that we know more about the energy, arrangement and movement of particles in the different states of matter, we can use this to explain the different properties of solids, liquids and gases that we learned about in the previous lesson.

 

Solids

properties of solids

  • Property: Fixed shape
    Explanation: Particles are held in a fixed arrangement due to very strong attraction between them.
  • Property: Fixed volume
    Explanation: Particles are held tightly together due to very strong attraction between them; therefore they cannot move apart (to increase volume).
  • Property: Not easily compressed
    Explanation: Particles are packed closely together due to very strong attraction between them; therefore there is no space for them to move into (to decrease volume).
  • Property: High or very high density
    Explanation: Particles are packed closely together due to very strong attraction between them; therefore there are high numbers of particles in a given space.

 

(Image: PIRO4D, Pixabay)

 

Liquids

properties of liquids

  • Property: Variable shape
    Explanation: Particles have sufficient energy to slide past each other.
  • Property: Fixed volume
    Explanation: Particles are held together due to strong attraction between them; therefore they cannot move apart (to increase volume).
  • Property: Not easily compressed
    Explanation: Particles are packed closely together due to strong attraction between them; therefore there is no space for them to move into (to decrease volume).
  • Property: High density
    Explanation: Particles are packed closely together due to strong attraction between them; therefore there are high numbers of particles in a given space.

 

(Image: OpenClipart-Vectors, Pixabay)

 

Gases

properties of gases

  • Property: Variable shape
    Explanation: Particles have high energy and virtually no attraction between them; therefore they are free to move in all directions.
  • Property: Variable volume
    Explanation: Particles have high energy and virtually no attraction between them; therefore they are free to move apart (to increase volume).
  • Property: Easily compressed
    Explanation: Particles have high energy and virtually no attraction between them; therefore they are free to move apart. This results in large amounts of space between particles; therefore they can be easily pushed closer together.
  • Property: Very low density
    Explanation: Particles have high energy and virtually no attraction between them; therefore they are free to move apart. This results in low numbers of particles in a given space.

 

(Image: 3271136, Pixabay)

 

Summary

  • The particle model describes the energy, arrangement and movement of particles in solids, liquids and gases.
  • Particles in solids:
    • Have low kinetic energy.
    • Are very strongly attracted to each other.
    • Are closely packed, in a fixed arrangement.
    • Move by vibrating.
  • Particles in liquids:
    • Have medium kinetic energy.
    • Are strongly attracted to each other.
    • Are closely packed, in a free arrangement.
    • Move by sliding past one another.
  • Particles in gases:
    • Have high kinetic energy.
    • Are not attracted to each other.
    • Are spaced far apart, in a free arrangement.
    • Move in all directions.
  • The particle model accounts for the different properties of solids, liquids and gases, such as shape, compressibility and density.

 
aerosol spray

(Image: PiccoloNamek, Wikimedia Commons)

 

(Header image: geralt, Pixabay)

 

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