Notes For All Chapters – General Science Class 6
Substances in the Surroundings – Their States and Properties
1. States of Matter
Everything around us is made of matter, which can be in three states:
Solid – Fixed shape and size (e.g., stone, wood, iron).
Liquid – Takes the shape of the container (e.g., water, milk, oil).
Gas – Has no fixed shape or volume, spreads in all directions (e.g., air, steam).
2. Change of State
Matter can change from one state to another when heated or cooled:
Melting – Solid to liquid (e.g., ice to water).
Evaporation – Liquid to gas (e.g., water to steam).
Condensation – Gas to liquid (e.g., steam to water).
Freezing – Liquid to solid (e.g., water to ice).
Sublimation – Solid to gas directly (e.g., camphor, naphthalene balls).
3. Temperature and Thermometer
Temperature tells us how hot or cold something is.
Thermometer is used to measure temperature in degrees Celsius (°C).
Boiling point of water = 100°C.
Freezing point of water = 0°C.
4. Properties of Substances
Hardness – Some substances are hard (iron), while some are soft (rubber).
Brittleness – Some substances break easily (glass, chalk).
Elasticity – Some can stretch and return to shape (rubber band).
Fluidity – Liquids flow and take the shape of the container.
Solubility – Some substances dissolve in water (salt, sugar), some do not (sand, oil).
Transparency – Some substances allow light to pass (glass), some do not (wood, metal).
5. Properties of Metals
Malleability – Can be beaten into thin sheets (gold, iron).
Ductility – Can be stretched into wires (copper, silver).
Conductivity – Metals conduct heat and electricity.
Lustre – Metals are shiny.
Sonority – Metals make a ringing sound when hit.
6. Everyday Uses of Changes in State
Candles are made by melting wax.
Dry ice (solid carbon dioxide) is used to keep things cold.
Glass is made by melting sand.
Metals like iron and gold are melted to make tools and jewelry.
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