Matter and Its States MCQs — Class 6 Science

Matter | NCERT CBSE Curriculum

Practice 100+ MCQs on Matter and Its States for Class 6 Science. Solids, liquids, gases, molecular model, Brownian motion, diffusion, surface tension - with instant answers and performance report.

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Quick Revision: Matter and Its States

  • Definition: Matter is anything which occupies space and has mass.
  • Ancient Views: Maharishi Kannada proposed matter is made of anu and parmanu. Democritus called the smallest particle an atom (indivisible).
  • Modern View: Molecules are the smallest particles capable of independent existence. Atoms combine to form molecules.
  • Particle Characteristics: Particles of matter are (i) very small in size, (ii) have spaces between them, (iii) in constant random motion, (iv) attract each other.
  • Brownian Motion: Random zig-zag motion of particles due to collisions with surrounding molecules. Visible in dust particles in sunlight or pollen in water.
  • Cohesion: Force of attraction between molecules of the same substance. Adhesion: Force between molecules of different substances.
  • Surface Tension: Liquid surface tends to occupy minimum surface area due to cohesion. Causes spherical drops and allows insects to walk on water.
  • Three States: Solids (definite shape & volume), Liquids (definite volume, no shape), Gases (no definite shape or volume).
  • Fourth State — Plasma: Found at very high temperatures. Consists of positive ions and free electrons. Example: stars, lightning.
  • Change of State: Melting (solid→liquid), Boiling/Vaporisation (liquid→gas), Condensation (gas→liquid), Freezing (liquid→solid).
  • Solids: Strong inter-molecular forces, negligible inter-molecular space, molecules vibrate at fixed positions. Low thermal expansion. Exert pressure only downwards.
  • Liquids: Weaker forces than solids, molecules move within boundary. Have one free surface. Exert pressure in all directions. Show viscosity and surface tension.
  • Gases: Negligible inter-molecular forces, molecules far apart. Highly compressible. Exert pressure on walls via continuous collisions. Very fast diffusion.
  • Nanoparticles: A molecule or cluster of molecules at nanoscale (10⁻⁹ m).

Chapter Summary: Matter and Its States

Matter is defined as anything that occupies space and has mass. Ancient Indian philosopher Maharishi Kannada was the first to propose that matter is composed of tiny particles called anu and parmanu. Later, Greek thinker Democritus named the smallest indivisible particle the atom. Modern science confirms that molecules—clusters of atoms—are the smallest particles capable of independent existence.

Particles of matter exhibit four key characteristics: they are extremely small (about 10⁻¹⁰ m in diameter), have spaces between them (shown by the salt-dissolving experiment), are in constant random motion (Brownian motion), and attract each other through cohesive and adhesive forces. These inter-molecular forces determine the three primary states of matter: solids (strong forces, closely packed, definite shape), liquids (moderate forces, flow and take container shape), and gases (negligible forces, fill all available space). A fourth state, plasma, exists at extremely high temperatures and contains ions and free electrons. Understanding the molecular model helps explain everyday phenomena: why water forms spherical drops (surface tension), why mercury doesn't stick to glass (cohesion > adhesion), and why gases are compressible while solids are not.

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