CBSE Class 9 Science Notes Chapter 1 Matter In Our Surroundings

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 Chemistry  

CBSE Class 9 Science Notes Chapter 1 Matter In Our Surroundings

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Matter in Our Surroundings

Chapter Overview:
This chapter focuses on the properties of matter, its states, and how matter behaves in different conditions. You’ll learn about the three main states of matter (solid, liquid, gas), as well as some basic concepts like diffusion, the effect of temperature on matter, and the process of change of states.

1. What is Matter?

  • Matter is anything that has mass and occupies space.

  • Examples: Water, air, food, etc.

2. Characteristics of Matter

  • Made up of particles: Matter is made up of tiny particles that are always in motion.

  • Particle Interaction: Particles in matter are bound by forces. These forces vary in strength depending on the state of matter.

    • In solids, particles are tightly packed.

    • In liquids, particles are loosely packed.

    • In gases, particles are very far apart.

3. States of Matter

  • Solid:

    • Fixed shape and volume.

    • Particles are very close together and vibrate in place.

  • Liquid:

    • Fixed volume, but takes the shape of the container.

    • Particles are close but can slide past each other.

  • Gas:

    • No fixed shape or volume.

    • Particles are very far apart and move freely.

Changes in States of Matter:

  • 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 vapor).

  • Condensation: Gas to liquid (e.g., water vapor to droplets).

  • Sublimation: Solid to gas (e.g., dry ice).

  • Deposition: Gas to solid (e.g., frost forming on a surface).

4. Properties of Matter

  • Physical Properties:

    • Shape, size, color, texture, and density.

    • Can be observed without changing the substance (e.g., melting point, boiling point).

  • Chemical Properties:

    • How matter reacts with other substances (e.g., rusting of iron, combustion).

5. Diffusion

  • Diffusion is the process where particles spread from an area of high concentration to an area of low concentration.

    • In gases, diffusion happens faster due to more movement of particles.

    • Example: When you open a perfume bottle, the fragrance spreads out in the air.

6. Effects of Temperature on Matter

  • On solids: When heated, the particles vibrate faster, and eventually, the solid melts.

  • On liquids: Heating a liquid increases particle movement, which can lead to evaporation.

  • On gases: Heating increases particle movement significantly, causing gas to expand.

7. Evaporation and Factors Affecting Evaporation

  • Evaporation is the process in which liquid changes into gas at the surface.

  • Factors affecting evaporation:

    • Surface area: More surface area leads to faster evaporation.

    • Temperature: Higher temperature increases the rate of evaporation.

    • Humidity: Higher humidity slows down evaporation.

    • Wind speed: Faster winds increase evaporation.

8. Liquefaction

  • Liquefaction is the process of converting a gas to a liquid by cooling or compressing it.

    • Example: Liquid nitrogen.

9. Conclusion

  • Matter exists in three primary states—solid, liquid, and gas—and can change from one state to another due to changes in temperature and pressure.

  • The microscopic behavior of particles helps explain the macroscopic properties of matter like shape, volume, and the ability to flow.

Important Definitions:

  • Matter: Anything that has mass and occupies space.

  • Diffusion: Movement of particles from an area of higher concentration to lower concentration.

  • Evaporation: The process where liquid changes into gas at the surface.

  • Melting Point: The temperature at which a solid turns into a liquid.





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