Class 8 Science Notes on Chapter 7 Particulate Nature of Matter: Yours Complete Study Guide For Exam

Everything around you, the air, the water, even the chair you are sitting on, is made of matter. But what really is matter made of? In this chapter we learn that everything is made of tiny particles. These tiny particles are always moving ,even when something looks completely still . 

In Class 8 Science Notes on Chapter 7 Particulate Nature of Matter, you will learn about the arrangement of particles in solids, liquids and gases, the forces of attraction between them andmore. These notes are simple so you can revise quickly and feel prepared for your exams.

Topics Covered in Class 8 Science Notes on Chapter 7 Particulate Nature of Matter 

What is Matter	Constituent Particles of Matter
Characteristics of Particles of Matter	Interparticle Forces of Attraction
Different States of Matter	Properties of Solids
Properties of Liquids	Properties of Gases
Movement and Mixing of Particles	Diffusion in Matter
Effect of Temperature on Particle Movement	Difference Between Solids, Liquids and Gases

What is Matter

Matter is anything that has mass and occupies space. Everything around us, including air, water, rocks, plants, animals and even our own bodies, is made of matter. Although matter appears continuous to our eyes, it is actually made up of extremely tiny particles that cannot be seen without powerful scientific instruments.

The idea that matter is made of tiny particles is known as the particulate nature of matter. These particles are so small that millions of them can fit into a tiny grain of sand. Scientists have discovered that the behaviour of these particles determines the physical properties of matter.

Matter exists in different forms, but all forms are made of particles that:

• Have mass.
• Occupy space.
• Are constantly moving.
• Have spaces between them.
• Attract one another.

Constituent Particles of Matter

Every substance is made up of tiny particles known as constituent particles. Depending on the substance, these particles may be atoms, molecules, or ions.

For example:

• Oxygen gas consists of oxygen molecules.
• Water consists of water molecules.
• Iron consists of iron atoms.
• Common salt consists of sodium and chloride ions.

Although these particles are extremely small, they possess several important characteristics.

Characteristics of Particles of Matter

1. Particles of Matter are Extremely Small

The particles that make up matter are too tiny to be seen with the naked eye. Even a small drop of water contains billions of water molecules.

Example: A tiny crystal of potassium permanganate can colour a large volume of water because its particles spread throughout the water.

2. Particles of Matter Have Spaces Between Them

There are empty spaces between the particles of matter. The amount of space depends on the state of matter.

For example:

• Solids have very little space between particles.
• Liquids have moderate spaces.
• Gases have large spaces between particles.

3. Particles of Matter are in Continuous Motion

The particles of matter are always moving. Their movement increases when the temperature increases because they gain kinetic energy.This continuous movement explains why substances spread on their own.

Example:

• The smell of perfume spreads throughout the room.
• The aroma of freshly cooked food reaches people sitting far away.

4. Particles of Matter Attract Each Other

Particles exert attractive forces on one another. This force keeps the particles together.

The strength of attraction varies in different states:

• Strongest in solids
• Moderate in liquids
• Weakest in gases

This is why solids maintain their shape while gases spread freely.

Interparticle Forces of Attraction

The particles of matter are separated by spaces known as interparticle spaces. The amount of space between particles and the force of attraction between them vary in solids, liquids and gases. 

These differences are responsible for their unique properties.

In solids, the particles are packed very closely together with the least amount of space between them. They have the strongest force of attraction, which makes solids rigid, gives them a definite shape and volume and makes them almost incompressible.

In liquids, the particles have slightly larger spaces between them. The force of attraction is weaker than in solids, allowing the particles to move past one another. As a result, liquids can flow and take the shape of their container while maintaining a fixed volume.

In gases, the particles are very far apart and have the weakest force of attraction. They move freely in all directions, which makes gases highly compressible and allows them to fill the entire container.

Comparison of Interparticle Spacing and Force of Attraction

Property	Solids	Liquids	Gases
Interparticle Spacing	Very small	Moderate	Very large
Force of Attraction	Very strong	Moderate	Very weak
Compressibility	Almost incompressible	Slightly compressible	Highly compressible

Different States of Matter

Matter mainly exists in three physical states:

• Solid
• Liquid
• Gas

Solid State and its Properties

A solid is a state of matter in which particles are packed very closely together. They cannot move freely and only vibrate about their fixed positions.

Properties of Solids

• Solids have a definite shape and volume.
• They are rigid and cannot flow.
• Their particles are tightly packed.
• They are almost incompressible.
• They have the strongest force of attraction among particles.

Examples

• Ice, Wood, Stone, Iron and Brick

Liquid State and its Properties

Liquids have particles that are close together but not fixed. They can move past one another, allowing liquids to flow.

Properties of Liquids

• Liquids have a definite volume but no definite shape.
• They take the shape of their container.
• Their particles can move freely.
• They can flow easily.
• They are only slightly compressible.

Examples

• Water, Milk, Oil, Juice and Petrol

Gaseous State and its Properties

Gases have particles that are far apart and move freely in all directions. They have very weak intermolecular forces.

Properties of Gases

• Gases have neither a definite shape nor a definite volume.
• They spread rapidly in all directions.
• They are highly compressible.
• Their particles move at very high speed.
• They occupy all the available space in a container.

Examples

Oxygen, Nitrogen, Carbon dioxide, Hydrogen and Water vapour

Movement and Mixing of Particles

The particles of matter are always in continuous motion. Their movement depends on the state of matter and the temperature. Gas particles move the fastest, liquid particles move more slowly and solid particles only vibrate about their fixed positions.

Because the particles are constantly moving, they can mix with one another without being stirred. This movement of particles from one place to another is called diffusion.

The activity of Potassium Permanganate in Water illustrates that When a few crystals of potassium permanganate are added to a beaker of water, the purple colour gradually spreads throughout the water even without stirring. This happens because the particles of potassium permanganate move continuously and mix with the water particles.

This activity proves that:

• Matter is made up of tiny particles.
• The particles of matter are always moving.
• There are spaces between the particles that allow mixing to occur.

Effect of Temperature on Particle Movement

The movement of particles increases with temperature. When water is warm, its particles have more kinetic energy and move faster, allowing substances to mix more quickly than they do in cold water.

For example, sugar dissolves faster in warm water than in cold water because the water particles move more rapidly.

Diffusion in Gases

Diffusion occurs fastest in gases because gas particles have the largest spaces between them and move at very high speeds.

Example: When an incense stick is lit or perfume is sprayed in one corner of a room, its fragrance quickly spreads throughout the room. This happens because the gas particles move rapidly and mix with the air.

Thus, diffusion is a characteristic property of liquids and gases, although it occurs much more rapidly in gases due to the greater speed of their particles.

Difference Between Solids, Liquids and Gases

Property	Solid	Liquid	Gas
Shape	Definite	No definite shape	No definite shape
Volume	Definite	Definite	No definite volume
Particle Arrangement	Closely packed	Loosely packed	Very far apart
Movement of Particles	Vibrate in fixed positions	Slide past one another	Move freely in all directions
Force of Attraction	Strong	Moderate	Weak
Compressibility	Negligible	Very low	High
Diffusion	Very slow	Moderate	Fast
Density	High	Moderate	Low