Change of State: Sublimation MCQs Quiz | Class 9

Test your understanding of Class IX Science (Code 086), Unit I: Matter – Its Nature and Behaviour. This quiz focuses on Sublimation, covering examples, definitions, and recognition-based questions. Complete the 10 questions below, check your score, and download the solution PDF for revision.

Overview of Sublimation

In the study of Matter: Its Nature and Behaviour (Unit I), sublimation is a unique physical change. While most substances change from solid to liquid and then to gas upon heating, some solids change directly into vapors on heating and vapors change directly into solids on cooling. This process is called sublimation.

Key Concepts & Examples

Understanding sublimation helps in separating mixtures and understanding daily life phenomena. The reverse process, where a gas changes directly to a solid, is technically called deposition, though sometimes the term sublimation is used for both directions in simpler contexts.

  • Ammonium Chloride (NH4Cl): A classic laboratory example. When heated, it turns directly into white fumes.
  • Camphor (Kapur): Used in prayers and household items; it disappears over time without leaving residue.
  • Naphthalene Balls: Used as moth repellents in clothes; they sublime over time, killing insects with their fumes.
  • Iodine: Shiny violet crystals that turn into violet vapor upon gentle heating.
  • Anthracene: Another organic compound that exhibits sublimation.
  • Dry Ice (Solid CO2): Solid carbon dioxide is called dry ice because it turns directly into gas under normal atmospheric pressure (1 atm), without melting into liquid.

Comparison of States

Process Initial State Final State Example
Melting Solid Liquid Ice to Water
Boiling Liquid Gas Water to Steam
Sublimation Solid Gas Dry Ice to CO2 Gas

Separation by Sublimation

This property is useful in separating mixtures that contain a sublimable volatile component from a non-sublimable impurity (like salt). For example, a mixture of ammonium chloride and common salt can be separated by heating the mixture in an inverted funnel setup.

Quick Revision Points

  • Sublimation involves skipping the liquid phase entirely.
  • Heat energy supplied is used to overcome the forces of attraction between solid particles rapidly.
  • Dry ice is stored under high pressure to keep it solid.
  • Naphthalene and Anthracene are organic examples.

Extra Practice Questions

1. Why does the size of naphthalene balls decrease after a few weeks?

2. How can you separate a mixture of iron filings and camphor?

3. What is the name of the process when iodine vapor turns back into solid crystals on a cool surface?

4. Why is solid carbon dioxide called dry ice?

5. Name two substances other than camphor that sublime.