Sublimation

Sublimation is the process in which a substance directly changes from solid to gas without becoming liquid.
This is a physical change and occurs in specific substances under certain conditions of pressure and temperature.
Sublimation is used in purification, printing, camphor production, and plays a role in rural household practices in Bihar.

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Key Characteristics of Sublimation

• Phase change: Solid → Gas (on heating)
• Reversible process → Gas → Solid (on cooling)
• No liquid phase involved
• It’s a physical change, not chemical

📝 PYQ (BPSC): Which process converts solid to gas directly? → Sublimation
📝 Expected MCQ: What type of change is sublimation? → Physical change

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Examples of Sublimation

• Camphor (Kapoor) – commonly used in Bihar temples
• Naphthalene balls – used in clothes to repel insects
• Dry ice (CO₂) – used in refrigeration, sublimates at room temp
• Iodine – used in chemistry labs
• Ammonium chloride – seen in school chemistry experiments

📝 PYQ (CDPO): Camphor shows which property? → Sublimation
📝 Expected MCQ: Which of these sublimes on heating? → Naphthalene

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Sublimation in Chemistry

• Used for purification of volatile solids (e.g., iodine, camphor)
• Helps separate sublimable compounds from non-sublimable ones
• Part of crystallization and compound isolation in labs

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Sublimation in Daily Life & Bihar Context

• Camphor is commonly used in rural Bihar homes for religious rituals → stored carefully due to sublimation
• Naphthalene balls are used in storage of woolens during long summers
• Traditional Ayurvedic medicines sometimes use sublimated ingredients
• Local science fairs and school projects often demonstrate sublimation using iodine or ammonium chloride

📝 Expected MCQ: What prevents camphor loss during storage? → Airtight containers (to prevent sublimation)

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Sublimation vs Evaporation

📝 Expected MCQ: Sublimation differs from evaporation in? → No liquid phase

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Uses of Sublimation

• Textile printing: Sublimation inks for digital printing
• Purification: Used in pharma and chemical industries
• Cooling: Dry ice used in transport of perishable items
• Science demos: Common in school chemistry labs

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PYQs + Expected MCQs

📝 PYQ (BPSC): Which of the following shows sublimation? → Camphor
📝 PYQ (CDPO): Use of naphthalene balls is based on? → Sublimation
📝 Expected MCQ: Sublimation is a type of...? → Physical change
📝 Expected MCQ: Which solid turns into gas without melting? → Iodine
📝 Expected MCQ: Which gas is used in dry ice? → Carbon dioxide

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Quick Revision Points

• Sublimation = Solid → Gas without liquid
• Examples: Camphor, Naphthalene, Dry ice, Iodine
• Physical, reversible change
• Used in: Purification, Storage, Printing
• Bihar use: Kapoor in rituals, Naphthalene for clothes
• Storage tip: Use airtight containers to prevent sublimation loss

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Sources Used

• NCERT Class 9 Science – Matter in Our Surroundings
• Lucent GK – Chemistry Section
• Drishti Science Quick Book
• EduTeria & Ghatna Chakra PYQs – BPSC, CDPO
• Bihar State Board Science Practice Book
• Local Home Science Projects – Bihar Science Exhibition Archives