ICSE Class 6 Chemistry: Pure Substances and Mixtures Short Notes | EduDias

⚡ Quick Revision: Pure Substances at a Glance

Pure Substance: A substance made of only one kind of particle and having fixed composition.

Element: A pure substance made of only one kind of atom.

Compound: A pure substance formed when two or more elements combine chemically in a fixed ratio.

Fixed Composition: The particles are present in a definite and unchanging ratio.

🔥 High-Yield Facts

• Elements and compounds are pure substances.
• Pure substances have fixed composition and definite properties.
• Water is pure only when it contains only H₂O particles.

🧪 Formula: Water → H₂O

Makeup: 2 Hydrogen atoms + 1 Oxygen atom

🧪 Formula: Carbon Dioxide → CO₂

Makeup: 1 Carbon atom + 2 Oxygen atoms

🧪 Formula: Common Salt → NaCl

Makeup: 1 Sodium atom + 1 Chlorine atom

🔄 Reaction: Formation of a Pure Compound

Hydrogen + Oxygen → Water

Observation: A compound is formed by chemical combination in a fixed ratio.

❌ DON'T CONFUSE:

Pure substance means one kind of particle vs Clean substance only means free from visible dirt.

⚠️ Exam Alert:

Do not write that filtered water is always a pure substance. It may still contain dissolved impurities.

🧠 MEMORY TRICK

ONE-FIX

ONE kind of particle and FIXed composition = pure substance.

Pure Substance	Type	Quick Recall
Oxygen	Element	One kind of atom
Iron	Element	Metal element
Water	Compound	H₂O 🔥
Common Salt	Compound	NaCl

[INSERT LABELED DIAGRAM: pure substance elements compounds one kind of particle fixed composition H2O NaCl oxygen iron]

🏷️ EXAM DIAGRAM: Pure Substances - Elements and Compounds

🚀 5 Things to Remember

• Pure substance has one kind of particle.
• Pure substance has fixed composition.
• Elements and compounds are pure substances.
• Water is H₂O.
• Common salt is NaCl.

⚡ Quick Revision: Mixtures at a Glance

Mixture: A substance made by physically combining two or more substances in any proportion.

Component: Each substance present in a mixture.

Variable Composition: The amount of each component can change from one mixture to another.

Physical Combination: Substances are mixed without forming a new substance.

🔥 High-Yield Facts

• Mixtures have variable composition.
• Components of a mixture can usually be separated by physical methods.
• Air, soil, salt water and lemonade are mixtures.

🧪 Formula Note: Mixture → Substance A + Substance B

Makeup: Components are physically mixed and keep their own properties.

🔄 Reaction: Salt Water Mixture

Salt + Water → Salt Water

Observation: Salt dissolves in water, but no new substance is formed.

❌ DON'T CONFUSE:

Mixture has variable composition vs Compound has fixed composition.

⚠️ Exam Alert:

Do not call air a compound. Air is a mixture of gases such as nitrogen, oxygen and carbon dioxide.

🧠 MEMORY TRICK

MIX-VAR

MIXtures have VARiable composition.

Mixture	Components	Quick Recall
Air	Nitrogen, oxygen, carbon dioxide	Mixture of gases 🔥
Salt Water	Salt + water	Salt can be recovered by evaporation
Soil	Sand, clay, minerals, humus	Non-uniform mixture
Lemonade	Water, sugar, lemon juice	Physical combination

[INSERT LABELED DIAGRAM: mixture examples air salt water soil lemonade components variable composition physical combination]

🏷️ EXAM DIAGRAM: Common Mixtures and Components

🚀 5 Things to Remember

• Mixture contains two or more substances.
• Mixtures are formed by physical combination.
• Mixtures have variable composition.
• Components of mixtures keep their properties.
• Air and salt water are mixtures.

⚡ Quick Revision: Types of Mixtures

Homogeneous Mixture: A mixture with uniform composition throughout.

Heterogeneous Mixture: A mixture with non-uniform composition and visible different parts.

Solution: A homogeneous mixture formed when a solute dissolves in a solvent.

Suspension: A heterogeneous mixture in which insoluble particles remain suspended for some time.

🔥 High-Yield Facts

• Salt water is a homogeneous mixture.
• Sand and water is a heterogeneous mixture.
• Homogeneous means uniform; heterogeneous means non-uniform.

🧪 Formula Note: Solution → Solute + Solvent

Makeup: Salt + Water → Salt Solution; sugar + water → Sugar Solution.

🔄 Reaction: Solution Formation

Sugar + Water → Sugar Solution

Observation: Sugar dissolves and forms a uniform mixture.

❌ DON'T CONFUSE:

Homogeneous means uniform throughout vs Heterogeneous means non-uniform with different visible parts.

⚠️ Exam Alert:

Do not call soil a homogeneous mixture. Soil has different visible particles, so it is heterogeneous.

🧠 MEMORY TRICK

HOMO = SAME, HETERO = DIFFERENT

Homo means same uniform look; Hetero means different visible parts.

Mixture Type	Composition	Example
Homogeneous	Uniform throughout	Salt water 🔥
Heterogeneous	Non-uniform	Soil, sand and water
Solution	Solute dissolved in solvent	Sugar solution
Suspension	Insoluble particles present	Muddy water

[INSERT LABELED DIAGRAM: homogeneous mixture uniform particles and heterogeneous mixture non uniform particles salt water soil sand water]

🏷️ EXAM DIAGRAM: Uniform and Non-Uniform Mixtures

🚀 5 Things to Remember

• Homogeneous mixture has uniform composition.
• Heterogeneous mixture has non-uniform composition.
• Salt water is homogeneous.
• Soil is heterogeneous.
• Solution = solute + solvent.

⚡ Quick Revision: Separation of Mixtures

Separation: The process of removing one component of a mixture from another.

Filtration: A method used to separate an insoluble solid from a liquid.

Evaporation: A method used to separate a dissolved solid from a solution by heating.

Decantation: Pouring out clear liquid after heavier solid particles settle down.

🔥 High-Yield Facts

• Mixtures can usually be separated by physical methods.
• Filtration separates sand from water.
• Evaporation separates salt from salt solution.

🧪 Formula Note: Filtration → Insoluble Solid + Liquid

Makeup: Sand + Water → Residue + Filtrate

🧪 Formula Note: Evaporation → Dissolved Solid + Liquid

Makeup: Salt Solution + Heat → Salt + Water Vapour

🔄 Reaction: Sand and Water Filtration

Sand + Water → Filtration → Sand Residue + Water Filtrate

Observation: Sand remains on filter paper and water passes through.

❌ DON'T CONFUSE:

Filtration removes insoluble solids vs Evaporation gets dissolved solids back.

⚠️ Exam Alert:

Do not use filtration to separate salt from salt water. Salt is dissolved, so evaporation is needed.

🧠 MEMORY TRICK

H-S-F-E-D

Handpick large solids, Sieve different sizes, Filter insoluble solids, Evaporate dissolved solids, Decant clear liquid.

Method	Used For	Example
Handpicking	Large visible solids	Stones from rice
Sieving	Different particle sizes	Bran from flour
Filtration	Insoluble solid + liquid	Sand from water 🔥
Evaporation	Dissolved solid + liquid	Salt from salt water
Decantation	Settled solid + clear liquid	Muddy water

[INSERT LABELED DIAGRAM: simple filtration setup funnel filter paper residue filtrate beaker sand water mixture]

🏷️ EXAM DIAGRAM: Simple Filtration Setup

🚀 5 Things to Remember

• Mixtures can be separated by physical methods.
• Filtration separates insoluble solid from liquid.
• Evaporation separates dissolved solid from solution.
• Decantation means pouring clear liquid after settling.
• Sand and water can be separated by filtration.

⚡ Quick Revision: Final Exam Recall Sheet

🔥 High-Yield Facts

• 🔥 Pure substances have fixed composition.
• 🔥 Mixtures have variable composition.
• 🔥 Mixtures can usually be separated by physical methods.

Pure Substance: One kind of particle with fixed composition.

Mixture: Two or more substances physically combined in any proportion.

Homogeneous Mixture: Uniform mixture throughout.

Heterogeneous Mixture: Non-uniform mixture with different visible parts.

🧪 Formula: Water → H₂O

Makeup: 2 Hydrogen atoms + 1 Oxygen atom

🧪 Formula: Common Salt → NaCl

Makeup: 1 Sodium atom + 1 Chlorine atom

🧪 Formula Note: Solution → Solute + Solvent

Makeup: Salt + Water → Salt Solution

🔄 Reaction: Filtration Recall

Sand + Water → Filtration → Sand Residue + Water Filtrate

Observation: Sand stays on filter paper and water passes through.

🔄 Reaction: Evaporation Recall

Salt Solution + Heat → Salt + Water Vapour

Observation: Water evaporates and salt remains behind.

❌ DON'T CONFUSE:

Compound has fixed composition and chemical combination vs Mixture has variable composition and physical combination.

⚠️ Exam Alert:

Do not write air as a pure substance. Air is a mixture of gases.

🧠 MEMORY TRICK

PURE-FIX | MIX-VAR

Pure substances are fixed; mixtures are variable.

Concept	Quick Recall	Example	Exam Trap
Pure Substance	Fixed composition	Oxygen, water	Clean water may not be pure
Mixture	Variable composition	Air, soil	Air is not a compound 🔥
Homogeneous	Uniform composition	Salt water	Looks same throughout
Heterogeneous	Non-uniform composition	Soil, muddy water	Different parts visible

Separation Method	Used For	Example
Handpicking	Large visible solids	Stones from rice
Filtration	Insoluble solid + liquid	Sand from water 🔥
Evaporation	Dissolved solid + liquid	Salt from salt water
Decantation	Settled solid + liquid	Muddy water

🧪 One-Glance Revision Flow

Matter → Pure Substance / Mixture → Homogeneous / Heterogeneous → Separation Method

[INSERT LABELED DIAGRAM: pure substances mixtures final revision map elements compounds homogeneous heterogeneous filtration evaporation]

🏷️ EXAM DIAGRAM: Pure Substances and Mixtures Revision Map

🚀 5 Things to Remember

• Pure substances have fixed composition.
• Mixtures have variable composition.
• Homogeneous mixtures are uniform.
• Heterogeneous mixtures are non-uniform.
• Mixtures can be separated by physical methods.