Science Class 9 - Matter In-Our-Surroundings Notes

Matter in Our Surroundings

Welcome to the chapter on Matter in Our Surroundings for Class 9. In this chapter, you will learn what matter is, its different states, how it changes from one state to another, and why these changes happen. By the end of this chapter, you will be able to explain the properties of solids, liquids, and gases, and understand the processes like melting, evaporation, and condensation.

Key Concepts

• Matter: Anything that has mass and occupies space.
• States of Matter: Solid, liquid, and gas.
• Physical Change: Change in state or appearance, but not in composition.

States of Matter

• Solids: Have a fixed shape and volume. Particles are closely packed.
• Liquids: Have a fixed volume but no fixed shape. Particles are less tightly packed than in solids.
• Gases: Have neither fixed shape nor fixed volume. Particles are far apart and move freely.

Change of State

• Melting: Solid to liquid (e.g., ice to water).
• Freezing: Liquid to solid (e.g., water to ice).
• Evaporation: Liquid to gas (e.g., water to water vapor).
• Condensation: Gas to liquid (e.g., water vapor to water).
• Sublimation: Solid to gas directly (e.g., camphor, dry ice).

Properties of Matter

• Particles of matter are very small.
• Particles of matter have spaces between them.
• Particles of matter are in constant motion.
• Particles of matter attract each other.

Applications and Examples

• Water changes from ice (solid) to liquid and then to vapor (gas).
• Air is a mixture of gases.
• Salt dissolves in water because of spaces between water particles.

Practice Questions

1. What is matter?
2. Name the three states of matter.
3. What is evaporation? Give one example.
4. How does ice change to water?
5. What is sublimation? Name one substance that shows sublimation.

Challenge Yourself

• Draw a diagram showing the change of states of matter.
• Explain why gases can be compressed easily but solids cannot.

Did You Know?

• Water is the only substance found naturally in all three states: solid, liquid, and gas.
• Dry ice is solid carbon dioxide and changes directly into gas.

Glossary

• Evaporation: The process by which a liquid changes into a gas.
• Condensation: The process by which a gas changes into a liquid.
• Sublimation: The process by which a solid changes directly into a gas.
• Particle: A very small part of matter.

Answers to Practice Questions

1. Anything that has mass and occupies space.
2. Solid, liquid, and gas.
3. Evaporation is the change of a liquid into a gas. Example: Drying of wet clothes.
4. By melting (when heat is given, ice melts to form water).
5. Sublimation is the change of a solid directly into a gas. Example: Camphor or dry ice.

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Explore the world around you and notice how matter changes its state!