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ICSE Class 7 Chemistry Question 10 of 14

Matter and Its Composition — Question 8

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Question 10

Describe simple experiments to show that —

(a) Particles of matter have intermolecular attraction.

(b) Particles of matter are closely packed in solids and less in liquids.

Answer

(a) Simple experiment to show that particles of matter have intermolecular attraction:

Procedure : Globules of mercury are placed in a petri dish and kept at a distance. Then the petri dish is shaken, and the mercury globules come together forming a big globule.

Conclusion : The above activity concludes that a force of attraction exists between the particles of matter.

(b) Simple experiment to show that particles of matter are closely packed in solids and less in liquids:

Procedure : 100 ml of water is taken in a measuring cylinder. Crystals of sugar (solid) are added to the water to obtain sugar solution. The volume of water, even after adding sugar remains the same at 100 ml.

Conclusion : This concludes that particles of matter are closely packed in solids and less closely packed in liquids. The sugar particles fill the intermolecular spaces which must be existing between the water molecules and hence the level of the water in the measuring cylinder does not rise.

ICSE Class VII Chemistry Chapter 1 15 Marks

Matter and Its Composition — Quick Study Guide

Everything around us is made of matter. Matter has mass and occupies space. It exists in three states: solid, liquid, and gas. Each state has unique properties based on how particles are arranged and move.

Key Definitions

  • Matter: Anything that has mass and occupies space
  • Solid: Fixed shape and volume, particles closely packed
  • Liquid: Fixed volume but no fixed shape, particles slide over each other
  • Gas: No fixed shape or volume, particles move freely
  • Diffusion: Spreading of particles from high concentration to low concentration
  • Sublimation: Direct change from solid to gas (e.g., camphor)
  • Latent heat: Heat absorbed during change of state without temperature change

Important Comparisons

Evaporation vs Boiling: Evaporation is a surface phenomenon at all temperatures (slow, no bubbles). Boiling occurs throughout the liquid at a specific temperature (rapid, with bubbles).

Exam Tips

  • Learn all six interconversion processes with examples
  • Practice questions on predicting state at a given temperature
  • Know factors affecting evaporation (4 factors)
  • Understand why pressure cooker cooks faster

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