Ch 1 explores the particle nature of matter. Students learn about the three states of matter, their properties, interconversion through heating/cooling, and phenomena like evaporation.
Matter is made of particles with spaces between them. Solids: tightly packed, fixed shape/volume, high density. Liquids: loosely packed, flow, take container shape, fixed volume. Gases: very loosely packed, occupy all available space, compressible.
Adding heat: solid → liquid (melting, at melting point) → gas (boiling/vaporisation, at boiling point). Removing heat: reverse happens (condensation, freezing). Sublimation: solid directly to gas (dry ice, camphor, naphthalene). Latent heat: energy needed for state change without temperature change.
Evaporation: liquid → gas at any temperature (from surface only). Rate increases with: higher temperature, larger surface area, lower humidity, more wind. Evaporation causes cooling (sweat cools the body as it evaporates).
Download: https://ncert.nic.in/textbook/pdf/iesc101.pdf | Complete book: https://ncert.nic.in/textbook/pdf/iesc1ps.zip
Ice at 0°C absorbs additional latent heat of fusion (334 J/g) as it melts, besides the heat needed to lower the temperature. Water at 0°C can only absorb sensible heat. So ice absorbs more total heat, providing more cooling.
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