01 Introduction to Chemistry
02 The Structure of Atoms
03 Concept of Mole, Formulae and Equations
04 Periodic Table of Elements
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2.1.1 The Particle Theory of Matter

The Particle Theory of Matter

  1. Matter is anything that occupies space and has mass.
  2. The particle theory of matter states that matter is made up of a large number of tiny and discrete particles.
Particle Theory of Matter: 
Matter is made up of a large number of tiny and discrete particles.

Types of Particles

  1. Particles can exist as atoms, molecules or ions.
  2. Atom is the smallest, indivisible particle of an element.
  3. Molecules are particles that made up of two or more atoms.
  4. Ions are particles that carry charge.
    1. Positive ion – Cation
    2. Negative ion – Anion


Diffusion and Brownian Motion

Proof of Particle Theory of Matter – Diffusion

In SPM, you need to know

  1. diffusion is one of the proofs of the particle theory of matter.
  2. the definition of diffusion.
  3. diffusion in solid, liquid and gas
  4. factors that affect the rate of diffusion and the related experiments.

What is Diffusion?

  1. Diffusion is a process of spreading a substance from a region of high concentration to a region of low concentration.
  2. It occurs when the particles of the substance move through the space between the particles of another substance.
  3. Figure below shows how the bromine particles diffuse into the air.
  4. Diffusion occurs in solid, liquid and gas.
  5. The rate of diffusion is highest in gas and lowest in solid.
  6. Diffusion is proof of the particle theory of matter.


  • The rate of diffusion is highest in gas and lowest in solid.
  • Diffusion is the proof of the particle theory of matter.

Interesting Video

Diffusion in Solid

Diffusion in Solid
The blue colour of copper(II) sulphate fills up the entire test tube after a few days
  • Copper(II) sulphate crystals are made of copper(II) ions and sulphate ions which are tiny and discrete.
  • The particles in the copper(II) sulphate crystal will separate to become ions and diffuse randomly upwards until the whole agar turns blue.

Diffusion in Liquid

(Diffusion in Liquid)
The purple colour of potassium manganate(VII) fills up the entire test tube after a few hours
  • Diffusion has taken place in the liquid.
  • The rate of diffusion of the particles in water is faster than the diffusion rate of particles in solid.
  • The occurrence of diffusion proves that potassium permanganate(VII) consist of tiny and discrete particles.

Diffusion in Gas

(Diffusion in Gas)
The brown colour bromine vapour spreads evenly throughout the gas jar in a few minutes
  • Bromine vapour is made of tiny and discrete molecules that move randomly to fill up space.
  • Bromine vapour moves randomly and diffuses in all directions in air from areas of higher concentration to areas of lower concentration.
Conclusion : The rate of diffusion is highest in gas and lowest in solid.

Brownian Motion

  1. Brownian motion is the physical phenomenon that tiny particles immersed in a fluid move about randomly.
  2. A fluid can be a liquid or a gas.
  3. Brownian movement, an example of diffusion, supports the kinetic theory of matter.
  4. Examples of Brownian movement are
    1. movement of smoke particles in air
    2. movement of pollen grains in water

Symbol of Elements

A symbol of element is the chemical symbol written in short form to represent a particular element. Some elements are represented by the first letter of its name. Examples:
Element Symbol
Fluorine F
Hydrogen H
Iodine I
Nitrogen N
Oxygen O
Phosphorus P
Sulphur S
Carbon C
Vanadium V
If there are two or more elements that have mane start with the same alphabet letter, a second letter is added to differentiate between these elements. The second letter used is always lowercase. Examples:
Elements Symbol
Bromine Br
Calcium Ca
Chlorine Cl
Chromium Cr
Magnesium Mg
Manganese Mn
Neon Ne
Nickel Ni
Silicon Si
Helium He
Argon Ar
Aluminium Al
Zinc Zn
Platinum Pt
Some elements are represented by their Latin names. Example:
Elements Latin Name Symbol
Copper Cuprum
Iron Ferrum
Lead Plumbum
Mercury Hydrargyrum
Potassium Kalium
Silver Argentum
Sodium Natrium
Tin Stannum
(Notes: You MUST Memorise the symbol for all these 31 elements)

Element and Compounds

Matter can be divided into elements and  compounds.


  1. An element is a substance that consists of only one type of atom.
  2. Element can be either atoms or molecules.
(Both the iron and oxygen are element because they consist of only one type of atoms)
  1. A compound is a substance composed of molecules made up of atoms of two or more elements.
  2. A compound is made up of either molecules or ions.
(Both the sodium chloride and carbon dioxide are compound because they consist of more than one type of atoms)