You know, matter, now it is the time to know what actually a matter is made of.

Particulate Nature of Matter Class 8 Chapter 7 takes you deep into the concept of matter. So, there will be new keywords and concepts to keep in mind.

And hence, we have created Particulate Nature of Matter Short Notes Class 8 to give you all the keywords and concepts in an easy-to-learn, memorise, and revise format. Read and understand your NCERT textbook.

Then, revise from the short notes below again and again to master Chapter 7 of the Science of Curiosity book.

The PDF of “Particulate Nature of Matter Short Notes Class 8” is at the end of the page.

Happy learning!

Table of Contents

What Is Matter Composed of?

Composition of Matter

Matter is composed of extremely small constituent particles – the basic building blocks of substances.

Grinding chalk = physical change (no new substance formed, only size reduction)

Constituent particles cannot be broken down further.

Sugar in Water Example

1. Sugar dissolves in water → breaks into constituent particles

2. Particles not visible but present (sensed by taste)

3. One sugar grain = millions of constituent particles

4. Sugar particles occupy the interparticle spaces between water particles

Key fact:
Particles cannot be seen through an ordinary microscope

Interparticle Forces

Interparticle attractions = attractive forces holding particles together

Strength depends on:

1. Nature of substance

2. Interparticle distance
(slight increase → drastic decrease in force)

Interparticle attractions decide the physical state of matter.

Three States of Matter

Solid State: Properties and Particle Behavior

Properties:

Definite shape
Definite volume

Particle behavior:

Tightly packed
Very strong interparticle attractions
Fixed positions
Only vibrate/oscillate
(cannot move past each other)

On heating:

1. Vibrations increase
2. Particles leave positions
3. Interparticle forces weaken
4. Converts to liquid

Melting point
minimum temperature for solid to liquid conversion at atmospheric pressure

Material	Melting Point
Ice	0 °C
Urea	133 °C
Iron	1538 °C

◾ Weak interparticle forces = low melting point.
◾ Strong interparticle forces = high melting point

Liquid State: Properties and Particle Behavior

Properties:

No fixed shape (takes container shape)
Definite volume

Particle behavior:

Free to move within a limited space
Somewhat farther apart
Interparticle attractions = slightly weaker
than solids
(but strong enough to keep particles close)

On heating:

1. Particles move vigorously
2. Move apart
3. Interparticle forces decrease
4. Converts to vapour/gas

Boiling point
The temperature at which a liquid changes to a vapour at atmospheric pressure

At boiling
point:

Vapour formation = very fast
Occurs at the surface + within the liquid
Visible as bubble formation

Below
boiling point:

Vapour formation = slow
Occurs only at the surface
Called evaporation

Gaseous States Properties and Particle Behavior

Properties:

No fixed shape
No fixed volume

Particle behavior:

Move freely in all directions
Negligible interparticle attractions

Fluids
liquids + gases (both flow, no fixed shape)

State Comparison

Property	Solid	Liquid	Gas
Shape	Fixed	Not fixed	Not fixed
Volume	Fixed	Fixed	Not fixed
Packing	Tightly packed	Somewhat apart	Very far apart
Interparticle Force	Very strong	Slightly weaker	Negligible
Movement	Vibrate in fixed positions	Free movement (limited space)	Free movement (all directions)

Key Terms

◼Interparticle spaces – Gaps between particles
◼Interparticle attractions – Attractive forces holding particles together
◼Interparticle distance – Distance between particles
◼Evaporation – Slow vapour formation below boiling point (surface only)
◼Fluids – Liquids + gases (flow, no fixed shape)
◼Vibrate/Oscillate – Move to and fro about a fixed position

How Does the Interparticle Spacing Differ in the Three States of Matter?

Compressibility

Gas
(Air)

Gas particles have a lot of space between them
Space can be reduced by external pressure
Stop pushing → particles spread

Liquid
(Water)

Water is practically incompressible

Dissolution of Sugar

Observation:

Initially, the water level increases when sugar is added
After dissolution, the level may decrease to some extent
Volume of solution < sum of water + sugar volumes

Conclusion:
Space exists between water particles → dissolved sugar particles occupy these spaces

Sand in Water

Sand = a solid that does not dissolve
Sand particles settle down
Occupy space in the container
Total volume increases

Interparticle Spacing in Solids

Particles held by strong forces of attraction
Do not move from place to place
Closely packed
Some space left between particles (despite close packing)
Space between particles ≠ of air
Contains nothing at all

Interparticle Spacing Summary

State	Particle Packing	Interparticle Space	Compressibility
Solid	Closely packed	Minimum space (some exists)	Not compressible
Liquid	Less closely packed	More space than solids	Practically incompressible
Gas	Very loosely packed	Maximum space (lot of space)	Highly compressible

How Particles Move in Different States
of Matter?

Particle Motion in Liquids

Potassium permanganate in water:

① Water particles are in constant motion

② Water particles pull out particles from the potassium permanganate grain

③ Water particles hit these particles

④ Particles spread throughout the liquid

Insoluble
substances
(like sand):

Constituent particles held together strongly
Water particles unable to pull these out
Remain insoluble

Particle Motion in Gases

Incense stick experiment:

Fragrance is first noticed near the incense stick.
Soon, it spreads across the whole room.
This happens because air particles are always moving.
They collide with fragrance particles and carry them everywhere.

Thermal Energy and States of Matter

Key principle:
The thermal (heat) energy of particles determines the physical state of matter.

Relationship:

Thermal energy determines the distance between particles
The distance between particles determines the strength of attractive forces

Solid State
Thermal Energy

Low thermal energy
Particles remain close to each other
Strong interparticle attractive forces
Motion restricted to small vibrations only

At the
melting point:

Thermal energy is used to
overcome attractive forces
Solid → liquid
Particles move away from fixed positions
Interparticle distance increases slightly
Strength of attractive forces reduces
Particles can move around
(within a limited space)

Liquid State
Thermal energy

Moderate thermal energy
Particles can move around
Movement within a limited space
Interparticle distance = slightly more than solids
Attractive forces = reduced but still present

Gaseous State
Thermal Energy

High thermal energy
Particles have enough energy
to overcome the forces of attraction
Move freely in all directions

Particle Nature Summary

State	Thermal Energy	Interparticle Distance	Attractive Forces	Particle Motion
Solid	Low	Minimum	Strong	Small vibrations only
Liquid	Moderate	Slightly increased	Reduced (still present)	Move around (limited space)
Gas	High	Maximum	Overcome (negligible)	Move freely (all directions)

FAQs: Particulate Nature of Matter Short Notes Class 8

1. Why can we compress air in a syringe but not water?

Gas particles naturally have a lot of space between them, which can be reduced by applying external pressure. When you push the plunger, the particles are forced closer together, decreasing the volume. Water is practically incompressible because liquid particles are already closely packed with minimal interparticle space.

2. What happens to sugar particles when sugar dissolves in water?

Sugar breaks into constituent particles that cannot be broken down further. These particles occupy interparticle spaces between water particles. Water particles are in constant motion – they pull out sugar particles from grains and hit them to spread throughout the liquid. Sugar becomes invisible but remains present (sensed by taste).

3. Why do solids have high melting points while some have low melting points?

Melting point depends on the strength of interparticle forces. Solids with weak interparticle attractions have low melting points (e.g., ice = 0°C). Solids with strong attractive forces have high melting points (e.g., iron = 1538°C). The stronger the forces holding particles together, the more thermal energy is needed to overcome them.

4. How does thermal energy determine the state of matter?

Thermal (heat) energy determines the distance between particles, which determines the strength of attractive forces. Solid state = low thermal energy → particles close → strong forces → small vibrations only. Liquid state = moderate thermal energy → slightly increased distance → reduced forces → movement within a limited space. Gaseous state = high thermal energy → particles overcome forces → free movement in all directions.

5. What is the difference between evaporation and boiling?

Boiling occurs at the boiling point – vapour formation is very fast, happens at surface + within liquid, visible as bubble formation. Evaporation occurs at all temperatures below boiling point – vapour formation is slow, occurs only at surface. Both convert liquid to vapour, but speed and location differ.

6. Why does the fragrance from an incense stick spread throughout the room?

Gas particles are in constant motion. Initially, fragrance is felt only around incense stick. Air particles moving constantly hit the fragrance particles and help them spread throughout the room. Gas particles have negligible interparticle attractions and move freely in all directions, allowing fragrance to fill entire space.

7. Why does grinding chalk only cause physical change and not chemical change?

Grinding chalk does not change it into a new substance – it remains chalk. Only the size of each speck reduces. Even after grinding to smallest possible size, you reach constituent particles that cannot be broken down further. Since no new substance forms and only physical appearance (size) changes, it is a physical change.

8. What happens to interparticle forces when a solid is heated to its melting point?

When solids are heated, particles vibrate more vigorously. At melting point, vibrations become so vigorous that particles start leaving their fixed positions. Interparticle forces of attraction weaken, and solid converts to liquid state. Thermal energy is used to overcome attractive forces between particles.

9. Why can you move your finger through water but not through a solid?

In liquids, interparticle attractions are slightly weaker than solids, but strong enough to keep particles close. When you move finger through water, you temporarily displace it. Position is restored when finger is removed. In solids, particles are in fixed positions with very strong interparticle attractions – they cannot be displaced without breaking/cutting permanently.

10. Why is the volume of the sugar solution less than the sum of the water and sugar volumes?

Water particles have interparticle spaces (gaps) between them. When sugar dissolves, sugar particles occupy these spaces instead of adding to total volume. Volume of solution is less than sum of water + sugar volumes because dissolved particles fit into existing spaces between water particles. This proves that space exists between particles of matter.