What are the three states of matter and their properties?

Solids: fixed shape and volume, incompressible, strong intermolecular forces. Liquids: fixed volume but no fixed shape, slightly compressible, moderate intermolecular forces. Gases: no fixed shape or volume, highly compressible, very weak intermolecular forces.

What is latent heat and why is it important?

Latent heat is the heat energy absorbed or released during a change of state at constant temperature. It is important because it explains why steam burns more than boiling water (steam has extra latent heat of vaporisation), and why ice at 0°C melts gradually rather than all at once.

What factors affect the rate of evaporation?

Four factors increase evaporation: (1) Increased surface area, (2) Higher temperature, (3) Lower humidity/wind speed increases, (4) Higher wind speed. Evaporation causes cooling because high-energy particles escape from the surface, lowering the average kinetic energy of remaining particles.

States of Matter

Matter in Our Surroundings • Class 9 Science • NCERT • CBSE

Matter exists in three states: solid, liquid, and gas. Solids have fixed shape and volume; liquids have fixed volume but take the shape of their container; gases have neither fixed shape nor volume. Matter can change state by absorbing or releasing heat energy.

Key Formulas

T(K) = T(°C) + 273 (Temperature conversion)
Solid → Liquid: Melting (absorbs heat)
Liquid → Gas: Vaporisation (absorbs heat)
Latent heat of fusion of water = 334 J/g
Latent heat of vaporisation of water = 2260 J/g

Frequently Asked Questions

What are the three states of matter and their properties?: Solids: fixed shape and volume, incompressible, strong intermolecular forces. Liquids: fixed volume but no fixed shape, slightly compressible, moderate intermolecular forces. Gases: no fixed shape or volume, highly compressible, very weak intermolecular forces.
What is latent heat and why is it important?: Latent heat is the heat energy absorbed or released during a change of state at constant temperature. It is important because it explains why steam burns more than boiling water (steam has extra latent heat of vaporisation), and why ice at 0°C melts gradually rather than all at once.
What factors affect the rate of evaporation?: Four factors increase evaporation: (1) Increased surface area, (2) Higher temperature, (3) Lower humidity/wind speed increases, (4) Higher wind speed. Evaporation causes cooling because high-energy particles escape from the surface, lowering the average kinetic energy of remaining particles.

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