A complete, beautifully organized guide to pure substances, mixtures, solutions, colloids, suspensions, and every separation technique you need to master.
Matter is anything that has mass and occupies space. All matter around us can be classified into two broad categories: Pure Substances and Impure Substances (Mixtures).
Consist of only one kind of particles. They have a fixed composition and definite properties.
Examples: Water (H2O), Iron (Fe), Gold (Au), Sodium Chloride (NaCl), Oxygen (O2), Sugar (C12H22O11), Copper (Cu), Aluminium (Al)
Also called Mixtures. Consist of two or more different types of particles physically combined.
Examples: Air, Sea water, Milk, Soil, Blood, Brass, Steel, Sand + Salt mixture
The simplest form of matter which cannot be broken down into simpler substances by chemical means.
Categories
Examples: Iron (Fe), Gold (Au), Oxygen (O), Carbon (C), Sodium (Na), Chlorine (Cl), Silicon (Si)
Substances formed when two or more elements chemically combine in a fixed ratio by mass.
Key Formula
Examples: Water (H2O), CO2, NaCl, H2SO4, NH3, CaCO3, C6H12O6
Important: Elements are made of one type of atom. Compounds are made of two or more types of atoms chemically bonded. Both are pure substances because they have fixed composition throughout.
Mixture is a substance formed by mixing two or more substances (elements or compounds) physically, without any chemical reaction. The components retain their individual properties.
A mixture with uniform composition throughout. You cannot see the individual components.
Examples: Salt water, Sugar solution, Air, Brass, Alloys, Vinegar
A mixture with non-uniform composition. You can visibly distinguish the different components.
Examples: Sand + Water, Oil + Water, Smoke, Milk, Blood, Soil, Paints
Key Point: The main difference is visibility. In a homogeneous mixture, you cannot see different parts. In a heterogeneous mixture, you can clearly see different substances mixed together.
Solution is a homogeneous mixture of two or more substances. The component present in larger amount is called the Solvent, and the one in smaller amount is called the Solute.
The substance that dissolves in the solvent.
Present in smaller quantity. Gets uniformly distributed in the solvent.
Example: In salt water, Salt is the solute.
The substance that dissolves the solute.
Present in larger quantity. Forms the bulk of the solution.
Example: In salt water, Water is the solvent.
The uniform mixture of solute and solvent.
Stable, transparent, and particles do not settle on standing.
Example: Salt water, Sugar solution, Air
| Type | Solute | Solvent | Example |
|---|---|---|---|
| Solid in Solid | Solid | Solid | Alloys (Brass, Bronze), Amalgam |
| Solid in Liquid | Solid | Liquid | Sugar in water, Salt in water |
| Solid in Gas | Solid | Gas | Camphor in air, Smoke |
| Liquid in Solid | Liquid | Solid | Hydrated salts, Cheese, Butter |
| Liquid in Liquid | Liquid | Liquid | Vinegar, Alcohol in water |
| Liquid in Gas | Liquid | Gas | Clouds, Fog, Humidity in air |
| Gas in Solid | Gas | Solid | Hydrogen in palladium, Foam rubber |
| Gas in Liquid | Gas | Liquid | Carbonated drinks, Soda water |
| Gas in Gas | Gas | Gas | Air (Oxygen + Nitrogen + others) |
Concentration refers to the amount of solute present in a given quantity of solution. It tells us how "strong" or "weak" a solution is.
A solution that contains the maximum amount of solute that can be dissolved at a given temperature.
No more solute can dissolve. Any extra solute will remain undissolved at the bottom.
Example: Sugar solution at 25°C where no more sugar dissolves.
A solution that contains less than the maximum amount of solute that can be dissolved.
More solute can still be dissolved in it at the same temperature.
Example: A dilute sugar solution where more sugar can still dissolve.
A solution that contains more solute than a saturated solution at the same temperature.
Prepared by heating a saturated solution and then cooling it slowly without disturbance. It is unstable — adding a crystal seed causes rapid crystallization.
Example: Sodium acetate supersaturated solution used in hand warmers.
Mass of solution = Mass of solute + Mass of solvent
Used for liquid-in-liquid solutions
Commonly used in medicine and pharmacy
Maximum amount of solute that can dissolve in 100g of solvent at a specific temperature.
Remember: Solubility generally increases with temperature for solids in liquids, but decreases for gases in liquids. Pressure affects the solubility of gases (Henry's Law).
Colloid (or Colloidal Solution) is a heterogeneous mixture in which the particles of the dispersed phase are uniformly distributed throughout the dispersion medium. The particle size ranges from 1 nm to 1000 nm (1 nm to 1 μm).
Brownian Motion: The random, zig-zag movement of colloidal particles. This motion keeps the particles from settling down and helps maintain the stability of the colloid.
A heterogeneous mixture in which solid particles are dispersed in a liquid or gas, but are large enough to settle down.
Examples: Sand in water, Chalk in water, Muddy water, Flour in water, Dust in air
A special type of colloid where liquid droplets are dispersed in another liquid. It is a liquid-liquid colloid.
Examples: Milk (fat in water), Butter, Mayonnaise, Hair cream, Face cream
Emulsifying agents: Soap, Detergents, Proteins (casein in milk), Lecithin
Tyndall Effect is the phenomenon of scattering of a beam of light by the particles of a colloid or suspension, making the path of light visible as a bright cone.
Distinguishing Test: Tyndall effect is used to distinguish between a true solution and a colloid. A true solution does NOT show Tyndall effect, while a colloid DOES. This is an important exam question!
Principle: Separation based on difference in boiling points. The volatile solvent evaporates leaving behind the non-volatile solute.
Used for: Separating a non-volatile solid from a volatile liquid.
Examples: Salt from sea water, Sugar from sugar solution, Obtaining salt from salt water.
Limitation: Cannot be used if the solute also decomposes on heating (e.g., sugar caramelizes).
Principle: Separation based on difference in boiling points of components. The mixture is heated, vaporized, and then condensed.
Used for: Separating components of a liquid mixture with different boiling points.
Examples: Purification of water, Separating alcohol and water, Obtaining petrol from crude oil.
Apparatus: Distillation flask, condenser, receiver, thermometer.
Principle: Used when the difference in boiling points is less than 25°C. A fractionating column provides multiple vaporization-condensation cycles.
Used for: Separating mixtures of miscible liquids with close boiling points.
Examples: Separating components of crude oil, Separating alcohol and water, Separating nitrogen and oxygen from liquid air.
Key Feature: Fractionating column with glass beads for better separation.
Principle: Separation based on difference in rates of absorption/adsorption of different components on a stationary phase.
Used for: Separating coloured components or substances with similar properties.
Types: Paper chromatography, Thin layer chromatography (TLC), Column chromatography, Gas chromatography.
Examples: Separating pigments from flowers, Detecting adulterants in food, Separating amino acids.
Principle: Separation based on the property of sublimation — direct conversion from solid to gas without melting.
Used for: Separating a sublimable solid from a non-sublimable solid.
Examples: Ammonium chloride from salt, Iodine from sand, Naphthalene from salt, Camphor from sand.
Apparatus: Sublimation apparatus with an inverted funnel and cotton plug.
Principle: Separation based on difference in solubility at different temperatures. Pure crystals form as solution cools.
Used for: Obtaining pure solid crystals from an impure solution.
Examples: Purification of salt, Obtaining alum crystals, Purification of copper sulphate, Rock candy (sugar crystals).
Advantage: Better than evaporation — prevents decomposition of heat-sensitive substances.
Principle: Separation based on size, shape, and colour differences.
Used for: Separating solid particles that are large enough to be picked by hand and visibly different.
Examples: Removing stones from rice/pulses, Separating rotten grains, Removing husks from grains.
Limitation: Only for small quantities and large particle sizes.
Threshing: Separating grains from stalks by beating or using a thresher machine.
Winnowing: Separating lighter husk from heavier grains using wind or air current.
Principle: Difference in weight/density of components.
Examples: Separating wheat grains from husk, Rice processing.
Principle: Separation based on difference in particle size.
Used for: Separating fine particles from coarse particles using a sieve.
Examples: Separating sand from gravel, Flour sieving, Removing bran from flour, Separating pebbles from sand.
Sieve size: Depends on the size of particles to be separated.
Principle: Separation based on difference in magnetic properties.
Used for: Separating magnetic substances from non-magnetic substances.
Examples: Iron from sand, Iron filings from sulphur powder, Removing iron pins from sand, Separating magnetic ores.
Apparatus: Magnet or magnetic separator.
Principle: Separation based on difference in particle size. The filter allows smaller particles to pass while retaining larger ones.
Used for: Separating an insoluble solid from a liquid.
Examples: Sand from water, Tea leaves from tea, Chalk from water, Removing dust from air.
Filter media: Filter paper, cloth, sand bed, charcoal.
Sedimentation: Allowing heavier insoluble particles to settle down at the bottom due to gravity.
Decantation: Carefully pouring out the clear liquid without disturbing the sediment.
Examples: Sand from water, Mud from water, Settling of dust in water treatment.
Combined with: Often followed by filtration for complete separation.
Principle: Separation based on difference in density using rapid rotation (centrifugal force).
Used for: Separating components of a mixture when sedimentation is too slow or for small quantities.
Examples: Separating cream from milk, Drying clothes in washing machine, Separating blood components, Removing water from lettuce.
Apparatus: Centrifuge machine.
Principle: Separation based on difference in density of immiscible liquids.
Used for: Separating two immiscible liquids that form distinct layers.
Examples: Oil and water, Kerosene and water, Petrol and water, Toluene and water.
Method: The denser liquid forms the lower layer and is drained out first.
| Property | Pure Substance | Impure Substance (Mixture) |
|---|---|---|
| Composition | Fixed and definite composition | Variable composition; ratio can change |
| Components | Only one kind of particles | Two or more types of particles |
| Melting/Boiling Point | Fixed and sharp melting/boiling point | Melts/boils over a range of temperature |
| Homogeneity | Always homogeneous | Can be homogeneous or heterogeneous |
| Separation | Cannot be separated by physical methods | Can be separated by physical methods |
| Chemical Formula | Has a definite chemical formula | No definite chemical formula |
| Properties | Characteristic and definite properties | Properties depend on components |
| Examples | Water, Iron, Gold, NaCl, Sugar | Air, Sea water, Milk, Soil, Brass |
| Property | Element | Compound |
|---|---|---|
| Definition | Simplest form of matter; cannot be broken down further | Formed by chemical combination of two or more elements |
| Atoms | Made of only one kind of atoms | Made of two or more kinds of atoms |
| Formation | Cannot be formed by combining substances | Formed by chemical reaction of elements |
| Composition | Fixed (only one type of atom) | Fixed ratio by mass of elements |
| Breakdown | Cannot be broken down by chemical means | Can be broken down into elements by chemical methods |
| Representation | Represented by symbols (Fe, O, Au) | Represented by formulae (H2O, NaCl) |
| Properties | Properties of element are unique | Properties are different from constituent elements |
| Examples | Iron, Oxygen, Gold, Carbon, Sodium | Water, Salt, Carbon dioxide, Ammonia |
| Property | Homogeneous Mixture | Heterogeneous Mixture |
|---|---|---|
| Composition | Uniform composition throughout | Non-uniform composition; different in different parts |
| Visibility | Components not visible separately | Components visible separately |
| Phases | Single phase | Two or more phases |
| Particle Size | Very small particles (< 1 nm) | Larger particles (> 1 nm) |
| Tyndall Effect | Does NOT show Tyndall effect | May or may not show Tyndall effect |
| Stability | Stable; components do not settle | May be unstable; components may settle |
| Filtration | Cannot be separated by filtration | Can be separated by filtration (if suspension) |
| Examples | Salt water, Air, Sugar solution, Alloys | Sand in water, Oil in water, Smoke, Milk |
| Property | True Solution | Suspension | Colloid |
|---|---|---|---|
| Particle Size | < 1 nm (very small) | > 1000 nm (very large) | 1 nm — 1000 nm (intermediate) |
| Visibility | Particles not visible | Particles visible to naked eye | Particles visible under microscope |
| Tyndall Effect | Does NOT show | Shows Tyndall effect | Shows Tyndall effect |
| Stability | Very stable | Unstable; settles on standing | Stable; does not settle |
| Filtration | Passes through filter paper | Does NOT pass through filter paper | Passes through filter paper |
| Settling | Does not settle | Settles on standing | Does not settle |
| Appearance | Clear and transparent | Cloudy and opaque | Generally translucent |
| Nature | Homogeneous | Heterogeneous | Heterogeneous (appears homogeneous) |
| Examples | Salt water, Sugar solution, Air | Sand in water, Chalk in water, Muddy water | Milk, Fog, Smoke, Paint, Blood, Shaving cream |
| Property | Saturated | Unsaturated | Supersaturated |
|---|---|---|---|
| Solute Amount | Maximum amount dissolved | Less than maximum amount | More than maximum amount |
| Dissolving | No more solute can dissolve | More solute can still dissolve | Excess solute present; unstable |
| Stability | Stable | Stable | Unstable; crystallizes on disturbance |
| Preparation | Add solute until no more dissolves | Add less solute than needed | Heat saturated solution, then cool slowly |
| Examples | Salt water at room temp with excess salt | Dilute salt water | Sodium acetate solution, Sugar syrup |
| Property | Physical Change | Chemical Change |
|---|---|---|
| Nature | Only physical properties change | Chemical properties change; new substance forms |
| Reversibility | Usually reversible | Usually irreversible |
| Energy | Little or no energy change | Energy is absorbed or released |
| New Substance | No new substance is formed | New substance with new properties is formed |
| Mass | Mass remains same | Mass remains same (Law of Conservation) |
| Examples | Melting ice, Boiling water, Dissolving sugar, Cutting paper | Burning wood, Rusting iron, Cooking food, Digestion |