Particulate Nature of Matter

About this chapter

Particulate Nature of Matter is Chapter 7 of Class 8 Curiosity. Chalk that is ground until it cannot be broken further, and sugar that vanishes in water but is still tasted, take students to one idea — matter is made of an enormous number of tiny constituent particles held together by interparticle attractions. The strength of these attractions, set by interparticle distance, decides the physical state. Solids — minimum spacing, maximum attraction, fixed shape and volume, particles only vibrate. Liquids — more spacing, slightly weaker attraction, fixed volume, no fixed shape. Gases — maximum spacing, negligible attraction, no fixed shape or volume. Table 7.1 gives melting points (ice 0, urea 133, iron 1538 °C); ice is an exception. The syringe compresses air but not water; sugar dissolves and the level may fall; potassium permanganate diffuses faster in hot water; incense fills the room. Acharya Kanad's Parmanu is acknowledged. CTET Paper 2 tests state-property matches, spacing diagrams, melting and boiling reasoning, evaporation vs boiling, diffusion with temperature, and the exercise items on rice grains, ocean salt and candle-wax states.