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PPT: Matter in Our Surroundings

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FAQs on PPT: Matter in Our Surroundings

1. What is the difference between physical and chemical properties of matter?
Ans. Physical properties describe characteristics like colour, density, melting point, and boiling point that don't change the substance's identity-such as ice melting into water. Chemical properties describe how matter reacts with other substances, like rusting of iron or burning of wood, which transform it into new materials entirely.
2. How do particles in solids, liquids, and gases behave differently?
Ans. Particles in solids are tightly packed with fixed positions, vibrating in place and giving definite shape and volume. Liquid particles are loosely arranged, allowing movement and taking the container's shape while maintaining fixed volume. Gas particles move freely with maximum spaces between them, filling any container completely without fixed shape or volume.
3. Why does matter change state when heated or cooled?
Ans. Heat energy causes particles to move faster, weakening the forces holding them together. When sufficient energy is applied, particles gain mobility-solids become liquids (melting), then gases (evaporation). Cooling reverses this, slowing particle movement and strengthening intermolecular forces, causing gases to condense into liquids, then freeze into solids.
4. What's the difference between evaporation and boiling in CBSE Class 9 science?
Ans. Evaporation occurs at the surface of liquids at any temperature when particles gain enough energy to escape into the gas phase. Boiling happens throughout the entire liquid at a specific temperature (boiling point) when vapour pressure equals atmospheric pressure, producing visible bubbles and rapid phase change.
5. How do you identify whether something is matter or not based on its properties?
Ans. Matter is anything that occupies space and has mass, displaying properties like density, elasticity, and malleability. Light, sound, and heat are not matter-they're energy forms without mass or fixed volume. All physical substances around us-air, water, metals, soil-are matter because they possess measurable mass and occupy definite space.
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