✏️ Quick & colourful revision notes — by @edugrown
📚 Table of Contents
1
Classifying Mixtures
A mixture is made of two or more substances mixed physically. Based on composition, mixtures are of two types:
| Homogeneous Mixture | Heterogeneous Mixture |
|---|---|
| Uniform composition throughout (e.g. sugar solution) | Non-uniform composition (e.g. sand + water) |
| Particles not visible; also called a solution | Particles are visible & settle with time |
| Example: vinegar, soda, sugar-water | Example: muddy water, oil + water |
REMEMBER
A solution always remains homogeneous — same composition in the first sip and the last sip!
A solution always remains homogeneous — same composition in the first sip and the last sip!
2
Solutions & Concentration
KEY TERMS
Solute = substance that gets dissolved. Solvent = substance that dissolves the solute.
Concentration = amount of solute dissolved in a given amount of solvent/solution.
Solute = substance that gets dissolved. Solvent = substance that dissolves the solute.
Concentration = amount of solute dissolved in a given amount of solvent/solution.
🔹 Three Ways to Express Concentration (%)
MASS BY MASS %
% m/m = (Mass of solute ÷ Mass of solution) × 100
used for solids in solids/liquids — e.g. milk powder composition
MASS BY VOLUME %
% m/v = (Mass of solute ÷ Volume of solution) × 100
used in medicines/labs — e.g. 5% glucose IV solution
VOLUME BY VOLUME %
% v/v = (Volume of solute ÷ Volume of solution) × 100
used for miscible liquids — e.g. 5% v/v acetic acid in vinegar
GOOD TO KNOW
Numerically, % m/m and % w/w are the same — mass & weight are used interchangeably in daily/industrial use.
Numerically, % m/m and % w/w are the same — mass & weight are used interchangeably in daily/industrial use.
3
Solubility
DEFINITION
Solubility = maximum amount of solute that dissolves in a fixed amount (100 g/100 mL) of solvent at a given temperature.
A solution that cannot dissolve any more solute at that temperature is called saturated.
Solubility = maximum amount of solute that dissolves in a fixed amount (100 g/100 mL) of solvent at a given temperature.
A solution that cannot dissolve any more solute at that temperature is called saturated.
- Solubility of a solid in a liquid → generally increases with temperature.
- Solubility of a gas in a liquid → generally decreases with temperature.
- A solubility curve is a graph of solubility (g/100 g water) vs temperature (°C).
USE
Solubility differences at different temperatures is the whole principle behind crystallization!
Solubility differences at different temperatures is the whole principle behind crystallization!
4
Crystallization
DEFINITION
Process of forming crystals (particles arranged in a regular geometric pattern) from a saturated solution, by cooling it slowly.
Process of forming crystals (particles arranged in a regular geometric pattern) from a saturated solution, by cooling it slowly.
- Used to separate two solids (one present in small quantity), both soluble in the same solvent.
- Also used for purification of solids (removes soluble/insoluble impurities).
- Slow cooling → large, well-shaped crystals. Fast cooling → small, poorly-formed crystals.
- Natural crystals: rock salt, sugar candy (mishri), snowflakes, frost, quartz.
STEPS
Prepare saturated solution (hot) → Filter to remove insoluble impurities → Cool slowly → Filter & collect crystals → Dry.
Prepare saturated solution (hot) → Filter to remove insoluble impurities → Cool slowly → Filter & collect crystals → Dry.
5
Distillation
DEFINITION
Separates a homogeneous mixture of two miscible liquids by heating till the liquid with the lower boiling point vaporises, then cooling the vapour back to liquid.
Separates a homogeneous mixture of two miscible liquids by heating till the liquid with the lower boiling point vaporises, then cooling the vapour back to liquid.
- Works best when boiling points of the two liquids differ by at least ~25 °C.
- Can also separate a liquid from a solution containing dissolved solids.
- Fractional distillation — used when boiling point difference is less than 25 °C (e.g. separating petrol, diesel, kerosene from crude oil).
INDIA’S CONTRIBUTION
Mitti ka Ittar (earthy perfume) from Kannauj, UP, is made using the traditional Deg-Bhapka distillation method — capturing the fragrance of first rain on soil! 🌧️
Mitti ka Ittar (earthy perfume) from Kannauj, UP, is made using the traditional Deg-Bhapka distillation method — capturing the fragrance of first rain on soil! 🌧️
6
Paper Chromatography
DEFINITION
A technique to separate components of a mixture (like dyes/pigments) based on differences in how fast they move with a solvent through paper.
A technique to separate components of a mixture (like dyes/pigments) based on differences in how fast they move with a solvent through paper.
- “Chromatography” (Greek) = chroma (colour) + graphein (to write) → “writing with colour”.
- The solvent (e.g. water) rises up the paper by capillary action, carrying dissolved substances at different speeds → separates into spots/bands.
- Used to separate ink colours, plant pigments (chlorophyll in leaves), food dyes.
- Important: the solvent level must stay below the sample spot at the start — never above it!
7
Immiscible Liquids & Sublimation
🔹 Separating Funnel (Immiscible Liquids)
- Immiscible liquids do not mix — they form separate layers based on density (e.g. oil floats on water).
- A separating funnel is used — open the stopcock to drain the denser (lower) liquid first.
🔹 Sublimation
DEFINITION
Sublimation = solid changes directly to vapour (without becoming liquid) on heating, below its melting point.
Deposition = the reverse — vapour directly changes back to solid on cooling.
Sublimation = solid changes directly to vapour (without becoming liquid) on heating, below its melting point.
Deposition = the reverse — vapour directly changes back to solid on cooling.
- Used to separate a sublimable solid (camphor, naphthalene, dry ice) from a non-sublimable one (sand).
8
Suspensions & Centrifugation
DEFINITION
A suspension is a heterogeneous mixture where solid particles do not dissolve but remain suspended in the medium — visible to the naked eye, settle over time (e.g. muddy water, sawdust in water).
A suspension is a heterogeneous mixture where solid particles do not dissolve but remain suspended in the medium — visible to the naked eye, settle over time (e.g. muddy water, sawdust in water).
🔹 Centrifugation
PRINCIPLE
High-speed spinning → heavier particles move outward & settle
- Used to separate blood into plasma, RBCs, WBCs & platelets.
- Also used widely in dairies & chemical industries.
🔹 Coagulation
- Adding a coagulant (like alum/fitkari) makes fine suspended particles clump together and settle down (sedimentation).
- Example: purifying muddy water; making paneer from milk using lemon juice/vinegar as coagulant.
9
Colloids
A colloid is a mixture “in between” a solution and a suspension — e.g. blood, milk, tomato sauce, ice cream, fog, smoke.
| Property | Solution | Colloid | Suspension |
|---|---|---|---|
| Particle size | < 1 nm | 1 – 1000 nm | > 1000 nm |
| Visible to eye? | No | No | Yes |
| Settles on standing? | No | No | Yes |
| Separated by filtration? | No | No | Yes |
| Scatters light (Tyndall)? | No | Yes | Yes |
KEY TERMS
Dispersed phase = the solute-like component of a colloid. Dispersion medium = the substance in which it is dispersed.
When both phases are liquids → called an emulsion (e.g. milk = oil-in-water).
Dispersed phase = the solute-like component of a colloid. Dispersion medium = the substance in which it is dispersed.
When both phases are liquids → called an emulsion (e.g. milk = oil-in-water).
10
Tyndall Effect
DEFINITION
Tyndall Effect = scattering of a light beam by particles in a colloid or suspension, making its path visible. Named after scientist John Tyndall.
Tyndall Effect = scattering of a light beam by particles in a colloid or suspension, making its path visible. Named after scientist John Tyndall.
- Seen in: a light beam through a colloid/suspension, sunlight through tree leaves, headlight beams in fog/dust, stadium floodlights.
- NOT seen in true solutions — particles are too small (< 1 nm) to scatter light.
11
Quick Formula Sheet
| Concentration Type | Formula |
|---|---|
| Mass by mass % | (Mass of solute ÷ Mass of solution) × 100 |
| Mass by volume % | (Mass of solute ÷ Volume of solution) × 100 |
| Volume by volume % | (Volume of solute ÷ Volume of solution) × 100 |
| Method | Best For |
|---|---|
| Crystallization | Separating/purifying a solid from a saturated solution |
| Distillation | Two miscible liquids (Δ boiling pt ≥ 25 °C) |
| Fractional distillation | Miscible liquids (Δ boiling pt < 25 °C) |
| Paper chromatography | Separating dyes / pigments |
| Separating funnel | Two immiscible liquids |
| Sublimation | Sublimable solid + non-sublimable solid |
| Centrifugation | Fine suspended particles in a liquid (e.g. blood) |
| Coagulation | Clumping fine suspended impurities to settle them |
🧪 Homogeneous = Solution
🌫️ Heterogeneous = Suspension/Colloid
💎 Crystallization → pure solid
♨️ Distillation → boiling pt. diff.
🌀 Centrifugation → density diff.
✨ Tyndall Effect → light scattering
🎉 That’s a wrap!
Chapter 5 · Exploring Mixtures and their Separation — Notes by @edugrown