States of Matter: Solids, Liquids, Gases and Changes of State
Ice melts into water. Water boils into steam. Wet clothes dry in the sun. Camphor slowly disappears from an open packet. These everyday events all happen because matter can exist in different states and change from one state to another.
This chapter is one of the most important basics in science for Classes 6 to 10. It helps explain weather, cooking, cooling, heating, perfumes, clouds, pressure cookers, ice creams, and even stars.
Let us understand States of Matter: Solids, Liquids, Gases and Changes of State in simple English with examples, tables, diagrams, exam tips, solved questions, and practice questions.
What is matter?
Matter is anything that has mass and occupies space.
In simple words, if something has weight and takes up space, it is matter.
Examples of matter:
Air
Water
Stone
Milk
Pencil
Book
Chair
Sugar
Oxygen
Steam
Things that are not matter:
Light
Sound
Heat
Shadow
Thoughts
These do not have mass and do not occupy space in the same way matter does.
Matter is made of very tiny particles. These particles are too small to see with our eyes.
What are the three main states of matter?
The three main states of matter are:
Solids
Liquids
Gases
These states are different because their particles are arranged and move differently.
For example, water can exist in all three states:
State | Example of water | Particle condition |
Solid | Ice | Particles are closely packed |
Liquid | Water | Particles are close but can move around |
Gas | Water vapour or steam | Particles are far apart and move freely |
Particle nature of matter
Matter is made of tiny particles. These particles may be atoms, molecules, or ions.
The particle nature of matter explains many observations.
Particles of matter have space between them
When sugar dissolves in water, it disappears from sight. The sugar particles fit into the spaces between water particles.
This shows that particles of matter have spaces between them.
Particles of matter are always moving
The particles of matter do not stay completely still. They move all the time.
Particles in solids vibrate in fixed positions.
Particles in liquids move around each other.
Particles in gases move very fast in all directions.
Particles of matter attract each other
Particles pull each other with a force called intermolecular force.
This attraction is:
Strongest in solids
Weaker in liquids
Weakest in gases
Solids
A solid has a fixed shape and a fixed volume.
Examples:
Table
Brick
Ice cube
Book
Metal spoon
Pencil
Stone
Particle arrangement in solids
In solids, particles are packed very closely. They are arranged in a fixed pattern in many solids.
The particles cannot move freely. They only vibrate about their fixed positions.
Shape and volume of solids
Solids have:
Fixed shape
Fixed volume
A stone remains the same shape whether it is on a table, in a bag, or in a box.
Properties of solids
Solids usually have these properties:
They are rigid.
They cannot be compressed easily.
They do not flow.
They have high density compared to gases.
Their particles have strong attraction.
Examples of special solids
Some solids can be soft or flexible.
Examples:
Sponge
Rubber band
Cotton
Clay
A sponge can be compressed because it has tiny air spaces inside it. The solid material itself does not compress much, but the trapped air comes out.
Did You Know? Glass looks like a solid and behaves like a solid in daily life. It does not flow like a liquid at room temperature.
Liquids
A liquid has a fixed volume but no fixed shape.
Examples:
Water
Milk
Oil
Juice
Petrol
Honey
Particle arrangement in liquids
In liquids, particles are close together, but they are not fixed in one position.
They can slide past one another. This is why liquids can flow.
Shape and volume of liquids
Liquids have:
No fixed shape
Fixed volume
A liquid takes the shape of its container. If you pour water from a glass into a bowl, its shape changes, but the amount of water remains the same.
Properties of liquids
Liquids usually have these properties:
They flow.
They have fixed volume.
They take the shape of the container.
They are difficult to compress.
Their particle attraction is weaker than in solids but stronger than in gases.
Why do liquids flow?
Liquids flow because their particles can move around each other. The force of attraction is not strong enough to hold them in fixed positions.
Gases
A gas has no fixed shape and no fixed volume.
Examples:
Air
Oxygen
Carbon dioxide
Nitrogen
Water vapour
LPG
Helium
Particle arrangement in gases
In gases, particles are very far apart. They move freely and quickly in all directions.
They collide with each other and with the walls of the container.
Shape and volume of gases
Gases have:
No fixed shape
No fixed volume
A gas fills the entire container available to it. If perfume is sprayed in one corner of a room, its smell spreads throughout the room.
Properties of gases
Gases usually have these properties:
They flow easily.
They spread in all directions.
They can be compressed easily.
Their density is low.
Their particles move very fast.
The attraction between particles is very weak.
Solids vs liquids vs gases
Property | Solids | Liquids | Gases |
Shape | Fixed | Not fixed | Not fixed |
Volume | Fixed | Fixed | Not fixed |
Particle arrangement | Very closely packed | Close but not fixed | Very far apart |
Particle movement | Vibrate in fixed positions | Slide and move around | Move freely and fast |
Intermolecular force | Strong | Medium | Very weak |
Space between particles | Very small | More than solids | Very large |
Compressibility | Very low | Low | High |
Flow | Do not flow | Flow | Flow easily |
Example | Ice, stone | Water, oil | Air, steam |
Intermolecular forces and spaces between particles
Intermolecular forces are forces of attraction between particles of matter.
They decide how tightly particles stay together.
In solids
Attraction is strong.
Particles are tightly packed.
Spaces between particles are very small.
Shape and volume remain fixed.
In liquids
Attraction is moderate.
Particles stay close but can move.
Spaces are larger than in solids.
Liquids flow and take the shape of the container.
In gases
Attraction is very weak.
Particles are far apart.
Spaces are very large.
Gases spread and fill the container.
Effect of temperature on particle movement
Temperature affects how fast particles move.
When temperature increases:
Particles gain energy.
They move faster.
They move farther apart.
Matter may change state.
When temperature decreases:
Particles lose energy.
They move slower.
They come closer.
Matter may change into a more compact state.
Example:
Ice absorbs heat and melts into water.
Water absorbs more heat and changes into steam.
Steam loses heat and condenses into water.
Water loses more heat and freezes into ice.
Changes of state
A change of state happens when matter changes from one physical state to another.
Common changes of state include:
Melting
Freezing
Boiling
Evaporation
Condensation
Sublimation
Deposition
Most changes of state are physical changes because no new substance is formed.
For example, when ice melts, it becomes water. Both ice and water are made of the same substance.
Melting and freezing
What is melting?
Melting is the change of state from solid to liquid.
Example:
Ice changes into water.
Butter melts on a hot pan.
Wax melts near a flame.
When a solid is heated, its particles gain energy. They vibrate faster. At a certain temperature, the particles break out of their fixed positions and start moving around. The solid becomes a liquid.
What is freezing?
Freezing is the change of state from liquid to solid.
Example:
Water changes into ice in a freezer.
Melted wax becomes solid when cooled.
Ghee solidifies in cold weather.
When a liquid cools, its particles lose energy. They slow down and come closer. At a certain temperature, they get fixed in position and form a solid.
Melting point and boiling point
Melting point
The melting point is the fixed temperature at which a solid changes into a liquid.
For pure ice, the melting point is 0°C.
At 0°C, ice and water can exist together.
Boiling point
The boiling point is the fixed temperature at which a liquid changes into a gas throughout the liquid.
For pure water at normal atmospheric pressure, the boiling point is 100°C.
At 100°C, water changes into steam.
Substance | Melting point | Boiling point |
Water | 0°C | 100°C |
Oxygen | About minus 219°C | About minus 183°C |
Iron | About 1,538°C | About 2,862°C |
Exam tip: Melting point and boiling point can change if pressure changes or if impurities are added.
Boiling and evaporation
Both boiling and evaporation change a liquid into a gas, but they are not the same.
What is boiling?
Boiling is the rapid change of a liquid into gas at its boiling point.
Boiling occurs throughout the liquid.
Example:
Water boiling in a kettle
Milk boiling in a pan
During boiling, bubbles form inside the liquid and rise to the surface.
What is evaporation?
Evaporation is the slow change of a liquid into vapour from its surface at any temperature.
Example:
Wet clothes drying
Water disappearing from a puddle
Sweat drying from skin
Perfume spreading into air
Evaporation happens only at the surface of a liquid.
Evaporation vs boiling
Point of difference | Evaporation | Boiling |
Temperature | Can occur at any temperature | Occurs at a fixed boiling point |
Place | Only at the surface | Throughout the liquid |
Speed | Slow | Fast |
Bubble formation | No bubbles | Bubbles form |
Heat source | May happen without direct heating | Usually needs continuous heating |
Example | Wet clothes drying | Water boiling in a kettle |
Factors affecting evaporation
Evaporation becomes faster when:
Temperature increases
Higher temperature gives more energy to particles. This is why clothes dry faster in summer.
Surface area increases
A liquid spread over a larger area evaporates faster.
Example:
Water in a plate evaporates faster than water in a glass.
Wind speed increases
Moving air carries away water vapour. This helps more liquid evaporate.
Example:
Clothes dry faster on a windy day.
Humidity decreases
Humidity means the amount of water vapour in air.
If air is already full of water vapour, evaporation slows down. This is why clothes dry slowly during the monsoon.
Condensation
Condensation is the change of gas into liquid.
Examples:
Water droplets on the outside of a cold glass
Dew on grass in the morning
Clouds forming from water vapour
Steam forming water droplets on a steel plate
When gas cools, its particles lose energy. They slow down and come closer. The gas changes into liquid.
Did You Know? Clouds are made of tiny water droplets or ice crystals, not water vapour. Water vapour is invisible.
Sublimation and deposition
What is sublimation?
Sublimation is the change of state from solid directly into gas without becoming liquid.
Examples:
Camphor slowly disappearing
Naphthalene balls becoming smaller
Dry ice changing into carbon dioxide gas
What is deposition?
Deposition is the change of state from gas directly into solid without becoming liquid.
Examples:
Frost forming on very cold surfaces
Water vapour forming ice crystals in freezing conditions
Deposition is the reverse of sublimation.
Changes of state table
Change of state | From | To | Heat change | Example |
Melting | Solid | Liquid | Heat absorbed | Ice to water |
Freezing | Liquid | Solid | Heat released | Water to ice |
Boiling | Liquid | Gas | Heat absorbed | Water to steam |
Evaporation | Liquid | Gas | Heat absorbed | Wet clothes drying |
Condensation | Gas | Liquid | Heat released | Water droplets on cold glass |
Sublimation | Solid | Gas | Heat absorbed | Camphor to vapour |
Deposition | Gas | Solid | Heat released | Frost formation |
Are changes of state physical or chemical changes?
Changes of state are usually physical changes.
Why?
No new substance is formed.
The change is mostly reversible.
The chemical composition remains the same.
Example:
Ice, water, and steam are all forms of water. Their state changes, but the substance remains water.
Compare with chemical change
Burning paper is a chemical change. New substances such as ash, smoke, and gases are formed.
Melting wax is a physical change. Burning wax is a chemical change.
Latent heat explained simply
Latent heat is the heat absorbed or released during a change of state without changing temperature.
The word latent means hidden.
When ice melts at 0°C, it absorbs heat. But its temperature stays at 0°C until all the ice melts. The heat is used to break the strong attraction between particles, not to raise temperature.
Similarly, when water boils at 100°C, heat is used to change water into steam. The temperature remains 100°C during boiling at normal pressure.
Simple example
Imagine ice in a glass. If heat is supplied:
Ice warms up to 0°C.
Ice melts at 0°C.
Water warms up beyond 0°C.
During step 2, heat is entering, but temperature does not rise. This heat is latent heat.
Diffusion in solids, liquids, and gases
Diffusion is the spreading and mixing of particles from a region of higher concentration to a region of lower concentration.
Diffusion in gases
Diffusion is fastest in gases because gas particles move very fast and have large spaces between them.
Example:
Smell of perfume spreads across a room.
Smell of food spreads from the kitchen.
Diffusion in liquids
Diffusion is slower in liquids than in gases.
Example:
A drop of ink spreads in water.
Potassium permanganate colour spreads in water.
Diffusion in solids
Diffusion is very slow in solids because particles are tightly packed.
Example:
Some metals can slowly mix at their surfaces when kept in close contact for a long time.
State | Speed of diffusion | Reason |
Gas | Fastest | Particles move freely and quickly |
Liquid | Moderate | Particles can move but are close |
Solid | Slowest | Particles are tightly packed |
Everyday examples of changes of state
Everyday event | Change of state |
Ice cream melting | Melting |
Water freezing in an ice tray | Freezing |
Steam on a mirror becoming droplets | Condensation |
Wet clothes drying | Evaporation |
Water boiling in a kettle | Boiling |
Camphor disappearing | Sublimation |
Frost forming in cold places | Deposition |
Melted candle wax becoming hard | Freezing or solidification |
Dew on leaves | Condensation |
Sweat drying from skin | Evaporation |
Brief introduction to plasma and other states of matter
Solids, liquids, and gases are the three main states studied in school. There are other states too.
Plasma
Plasma is a very hot state of matter in which gas particles become charged.
Examples:
The Sun and stars
Lightning
Neon signs
Some parts of flames
Plasma is often called the fourth state of matter.
Bose-Einstein condensate
At extremely low temperatures, some substances form a special state called Bose-Einstein condensate. This is studied in higher classes and advanced physics.
For Classes 6 to 10, focus mainly on solids, liquids, gases, and changes of state.
Common misconceptions about matter and changes of state
Mistake 1. Air is not matter
Air is matter because it has mass and occupies space.
A balloon becomes bigger when filled with air. This shows air takes up space.
Mistake 2. Gases have no weight
Gases have weight, but many gases are very light. A filled LPG cylinder is heavier than an empty one.
Mistake 3. Boiling and evaporation are the same
Both form vapour, but evaporation happens at the surface at any temperature. Boiling happens throughout the liquid at its boiling point.
Mistake 4. Steam is always visible
Water vapour is invisible. The white cloud seen near a kettle is made of tiny water droplets formed by condensation.
Mistake 5. Temperature rises during melting
During melting, temperature remains constant until the whole solid melts, if the substance is pure and pressure is constant.
Mistake 6. All solids are hard
Some solids are soft, such as rubber, sponge, cotton, and wax. A solid has fixed shape and volume, but it need not always be hard.
Exam tips for Classes 6 to 10
Use the words fixed shape and fixed volume correctly.
Mention particle arrangement when comparing states.
Write that changes of state are physical changes.
In evaporation vs boiling, write at least three differences.
Do not confuse gas with vapour. Vapour is the gaseous form of a substance that is usually liquid or solid at room temperature.
Mention heat absorbed or heat released in change-of-state questions.
Give everyday examples wherever possible.
For diffusion, remember the order: gases fastest, liquids slower, solids slowest.
Quick revision notes
Matter has mass and occupies space.
Matter is made of tiny particles.
Particles have spaces between them.
Particles are always moving.
Particles attract each other.
Solids have fixed shape and fixed volume.
Liquids have fixed volume but no fixed shape.
Gases have no fixed shape and no fixed volume.
Heating increases particle movement.
Cooling decreases particle movement.
Melting is solid to liquid.
Freezing is liquid to solid.
Boiling is liquid to gas at boiling point.
Evaporation is liquid to gas from the surface at any temperature.
Condensation is gas to liquid.
Sublimation is solid to gas.
Deposition is gas to solid.
Changes of state are physical changes.
Latent heat changes state without changing temperature.
Diffusion is fastest in gases.
20 solved questions and examples
1. Define matter.
Matter is anything that has mass and occupies space. Examples include water, air, stone, and milk.
2. Why is air called matter?
Air has mass and occupies space. A balloon becomes larger when filled with air, which shows air takes up space.
3. Name the three main states of matter.
The three main states of matter are solid, liquid, and gas.
4. Why do solids have a fixed shape?
Solids have a fixed shape because their particles are tightly packed and can only vibrate in fixed positions.
5. Why do liquids flow?
Liquids flow because their particles can slide past one another.
6. Why can gases be compressed easily?
Gases can be compressed because there are large spaces between their particles.
7. What happens to particles when a substance is heated?
The particles gain energy and move faster.
8. What is melting?
Melting is the change of state from solid to liquid. Ice melting into water is an example.
9. What is freezing?
Freezing is the change of state from liquid to solid. Water becoming ice is an example.
10. What is boiling?
Boiling is the rapid change of a liquid into gas at its boiling point.
11. What is evaporation?
Evaporation is the change of a liquid into vapour from its surface at any temperature.
12. Give one difference between evaporation and boiling.
Evaporation occurs at any temperature, while boiling occurs at a fixed boiling point.
13. What is condensation?
Condensation is the change of gas into liquid. Water droplets on a cold glass are formed by condensation.
14. What is sublimation?
Sublimation is the change from solid directly into gas. Camphor shows sublimation.
15. What is deposition?
Deposition is the change from gas directly into solid. Frost formation is an example.
16. Are changes of state physical or chemical changes?
They are physical changes because no new substance is formed.
17. What is latent heat?
Latent heat is the heat absorbed or released during change of state without change in temperature.
18. Why do wet clothes dry faster in sunlight?
Sunlight increases temperature. This gives water particles more energy, so evaporation becomes faster.
19. Why does perfume smell spread in a room?
Perfume particles mix with air particles by diffusion and spread throughout the room.
20. Which state of matter has the strongest intermolecular force?
Solids have the strongest intermolecular force among the three main states.
10 FAQs
1. Is water matter?
Yes. Water has mass and occupies space, so it is matter.
2. Is heat matter?
No. Heat is a form of energy. It does not have mass or occupy space like matter.
3. Why does ice float on water?
Ice is less dense than liquid water. Its particles are arranged in a way that gives it more volume for the same mass.
4. Can a substance exist in all three states?
Yes. Water can exist as ice, liquid water, and water vapour.
5. Is evaporation a cooling process?
Yes. During evaporation, high-energy particles leave the liquid surface. The remaining liquid becomes cooler.
6. Why do we feel cool after sweating?
Sweat evaporates from the skin. It takes heat from the body, so we feel cool.
7. Why does water boil faster in a pressure cooker?
A pressure cooker increases pressure. This raises the boiling point of water, so food cooks faster at a higher temperature.
8. Is melting wax a physical change?
Yes. Melting wax is a physical change because no new substance is formed.
9. Is burning wax a physical change?
No. Burning wax is a chemical change because new substances are formed.
10. Which state has the fastest particles?
Gas particles usually move the fastest among solids, liquids, and gases.
25 practice questions
Define matter.
Give three examples of matter.
Give two examples of things that are not matter.
Name the three main states of matter.
Write two properties of solids.
Write two properties of liquids.
Write two properties of gases.
Why do gases fill the entire container?
Why are solids difficult to compress?
10. What is intermolecular force?
11. Arrange solids, liquids, and gases in increasing order of spaces between particles.
12. What happens to particle movement when temperature increases?
13. Define melting.
14. Define freezing.
15. What is the melting point of pure ice?
16. What is the boiling point of pure water at normal atmospheric pressure?
17. Define boiling.
18. Define evaporation.
19. Write two differences between evaporation and boiling.
20. Give two factors affecting evaporation.
21. Define condensation.
22. What is sublimation? Give one example.
23. What is deposition? Give one example.
24. Why are changes of state called physical changes?
25. What is diffusion? In which state is it fastest?
Answer key
Matter is anything that has mass and occupies space.
Water, air, stone.
Light and sound.
Solid, liquid, gas.
Fixed shape and fixed volume.
Fixed volume and ability to flow.
No fixed shape and no fixed volume.
Gas particles move freely and spread in all directions.
Their particles are tightly packed with very little space.
10. It is the force of attraction between particles.
11. Solids, liquids, gases.
12. Particles gain energy and move faster.
13. Melting is the change from solid to liquid.
14. Freezing is the change from liquid to solid.
15. 0°C.
16. 100°C.
17. Boiling is the rapid change of liquid into gas at its boiling point.
18. Evaporation is the change of liquid into vapour from the surface at any temperature.
19. Evaporation occurs at any temperature and only at the surface. Boiling occurs at boiling point and throughout the liquid.
20. Temperature and surface area. Wind speed and humidity are also correct.
21. Condensation is the change from gas to liquid.
22. Sublimation is solid directly changing into gas. Camphor is an example.
23. Deposition is gas directly changing into solid. Frost is an example.
24. No new substance is formed, and the change is usually reversible.
25. Diffusion is the spreading of particles from higher concentration to lower concentration. It is fastest in gases.
Conclusion
Matter is all around us, from the air we breathe to the water we drink and the books we read. The three main states of matter, solids, liquids, and gases, differ because of particle arrangement, particle movement, intermolecular forces, and spaces between particles.
Heating and cooling can change matter from one state to another. Melting, freezing, boiling, evaporation, condensation, sublimation, and deposition are physical changes because the substance remains the same.
A strong understanding of this chapter makes many science topics easier, including heat, weather, pressure, atoms, molecules, and chemical changes. For exams, focus on definitions, differences, examples, and particle-level explanations.
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