Kinetic Model Of Matter

In this article, we will be learning about the following topics:

• States of Matter
• The Kinetic Model of Matter
• Brownian Motion (experimental set-up)

We will be covering these topics as per the academic requirements of Secondary 3 Physics level.

States of Matter

The three states of matter are: Solid, Liquid, and Gas.

Water is the only substance on Earth that exists in all three states naturally.

It exists as ice (solid), water (liquid), and water vapour (gas) naturally.

The three states in the decreasing order of density are:

Practice Questions

Question 1:

Which row describing the properties of matter is correct?
 

Solution:

The correct option is A.

Kinetic Model of Matter

The Kinetic Model of Matter states that matter is made up of particles in constant random motion.

The model explains the properties of the three states.

The Solid State
	Particles vibrate about fixed positions. Fixed shape and volume. Particles are closely packed together in regular lattice structure. High density.
The Liquid State
	Particles glide and slide around each other. Fixed volume but no fixed shape. Particles randomly arranged and slightly farther apart. Lower density than solids.
The Gaseous State
	Particles move freely in all directions at high speeds. No fixed shape and volume. Particles are randomly arranged and far apart from one another. Lowest density of all three states.

The Three States of Matter

• For the solids, the particles are held tightly together by strong attractive forces. As a result, the particles can only vibrate about fixed positions. This accounts for their fixed shape and volume.
• For the liquids, the particles are held tightly together by relatively weaker attractive forces and therefore glide and slide about each other. This accounts for their fixed volume but no fixed shape.
• For the gases, the particles have negligible attractive forces between them. They can move freely at high speeds in all directions. This accounts for their non-fixed shape and volume.

Relationship between the Motion of Particles and Temperature

As temperature increases, the average kinetic energy increases, thus the motion of the particles increases.

As the temperature increases, there is more heat (since temperature is an indicator of heat). This heat energy gets converted into kinetic energy and hence the particles move faster.

Question 2:

Which of the following increases when the temperature of the substance increases?

1. Kinetic energy
2. Average kinetic energy
3. Potential energy
4. Total energy

Solution:

Option B is the correct answer.

Explanation:

In a substance, there are many particles. Their numbers may vary from 10⁹ or 10¹² or even more. Each particle will have its own kinetic energy. 

The temperature of the substance (as a whole of all the particles) will thus be dependent on the average of the kinetic energy of all the particles. 

Brownian Motion

Brownian motion refers to the random motion of particles, such as pollen and dust specks, suspended in fluids (e.g. air, water).

Brownian motion is the evidence of the Kinetic Model of Matter. We can see the dust particles suspended in the air and in random motion in front of a projector. When the projector shines its light on the screen, we can see the dust particles in the air and also their motion. This proves the theory of the kinetic energy model.

Experimental Set-up (Gas)

1. A small glass cell is filled with smoke.
2. Light is shone through the cell.
3. The smoke is viewed through a microscope.
4. Smoke particles (which appear as specks of light) can be observed to be constantly moving about and changing directions randomly.

Conclusion

In this article, we have learned about:

• The three states of matter 
  • Solid, Liquid, and Gas and their properties
• The Kinetic Model of Matter
  • How the particles move differently due to different forces of attraction
• Brownian Motion
  • Evidence of Kinetic Model of Energy
  • Experimental Set-up

All these topics are in accordance with the syllabus requirements of Secondary 3 Physics. We hope you have enjoyed this article and it has helped you to grasp these concepts better.