Ch 05: Solution & Colloid | Exam Fusion Prep

🧪 Chapter At a Glance

📘 Solution

Homogeneous mixture of two or more substances. Solute (less quantity) + Solvent (more quantity) → Solution. Universal Solvent = Water (H₂O).

Water

Universal Solvent

1–1000 nm

Colloid Particle Size

Tyndall

Effect in Colloid & Suspension

Centrifuge

Separates Colloid

📏 Particle Size Comparison

✅ TRUE SOLUTION
< 1 nm

🌫️ COLLOID
1 – 1000 nm

🪨 SUSPENSION
> 1000 nm

⚠️ Exam Trap — Particle Sizes

True solution: < 1 nm | Colloid: 1–1000 nm | Suspension: > 1000 nm
Tyndall Effect: Colloid ✓ and Suspension ✓; True Solution ✗
Visible to naked eye: Suspension ✓ only

💧 Solution — Basics

Solute

Dissolved substance (less quantity)

Soluble substance — dissolves in solvent
Insoluble substance — does NOT dissolve
e.g., Sugar, Salt, NaCl

Solvent

Dissolving medium (more quantity)

Universal solvent = Water (H₂O)
More quantity than solute
e.g., Water, Alcohol, Acetone

📘 Key Formula

Solute (less) + Solvent (more) → Solution

📂 Classification of Solutions

Solution Type	Solute	Solvent	Example
Solid Solution	Gas	Solid	Absorption of H₂ in Palladium (Pd)
	Liquid	Solid	Amalgam of Mercury with Sodium
	Solid	Solid	Zinc dissolved in Copper (Brass/alloys)
Liquid Solution	Gas	Liquid	O₂ dissolved in Water
	Liquid	Liquid	Alcohol solution in Water
	Solid	Liquid	Sugar solution in Water
Gaseous Solution	Gas	Gas	Air (mixture of gases)
	Liquid	Gas	Chloroform + N₂ → Fog
	Solid	Gas	Camphor + N₂ → Smoke

⚠️ Exam Trap — Solution Types

H₂ absorbed in Palladium (Pd) = Gas in Solid solution
Mercury amalgam with Na = Liquid in Solid solution
Air = Gas in Gas (gaseous solution)
Fog = Liquid in Gas | Smoke = Solid in Gas
O₂ in water = Gas in Liquid (fish breathe this dissolved O₂)

🌡️ Saturated vs Unsaturated Solution

Saturated Solution

No more solute can dissolve

At given temperature and pressure, maximum solute already dissolved
Adding more solute → remains undissolved
On increasing temperature → becomes Unsaturated (more can dissolve)

Unsaturated Solution

More solute can still dissolve

At given T and P, more solute can still be added
On decreasing temperature → becomes Saturated
Example: 30g NaCl + 100 ml H₂O = Unsaturated

📘 Temperature Effect on Solubility

Temperature increases → Saturated solution → becomes Unsaturated (capacity increases)
Temperature decreases → Unsaturated → becomes Saturated (capacity decreases)
Most solids: solubility increases with temperature
Gases in liquid: solubility decreases with temperature (carbonated drinks go flat when warm)

⚠️ Exam Trap

Temp ↑ → Saturated becomes Unsaturated (more dissolves)
Temp ↓ → Unsaturated becomes Saturated (less can dissolve)
Gas solubility in liquid: opposite — decreases with temp (O₂ in water)

📊 Solution vs Colloid vs Suspension

✅ True Solution

Homogeneous mixture
Particle size < 1 nm
No Tyndall Effect
Particles NOT visible
Cannot be separated by filtration
Examples: Sugar in water, Salt in water, NaCl(aq)

🌫️ Colloid

Appears homogeneous, actually heterogeneous
Particle size 1–1000 nm
Shows Tyndall Effect
Particles too small to see with naked eye
Separated by Centrifugation
Examples: Milk, Ink, Blood, Fog, Smoke

🪨 Suspension

Heterogeneous mixture
Particle size > 1000 nm
Shows Tyndall Effect
Particles visible to naked eye
Separated by Filtration
Examples: Chalk in water, Mud in water

⚠️ Exam Trap — Tyndall Effect

Tyndall Effect = scattering of light by colloidal particles
Shown by: Colloid ✓ and Suspension ✓
NOT shown by: True Solution ✗
Colloid separated by Centrifugation; Suspension by Filtration
Milk = Colloid (separated by centrifugation → butter/cream); NOT a true solution

🌫️ Colloid — Applications

Industrial / Technical Applications

Smoke precipitation (removing smoke from chimneys)
Purification of clothes (detergent action)
Stopping secretion of blood (FeCl₃ as coagulant)

Natural Applications

Rain formation — clouds are colloids
Blue colour of sky — Tyndall Effect (scattering)
Delta formation — colloidal river silt coagulates at sea

💡 Tyndall Effect

📘 Definition

Scattering of a beam of light by colloidal particles. Observed in Colloid and Suspension but NOT in a true solution.

Colloid particle size: 1 nm to 1000 nm
Examples: Beam of sunlight through dusty room, Headlights shining in fog
Blue colour of sky = Tyndall Effect (smaller wavelength blue light scattered more)
Smoke and fog visible from headlights = Tyndall Effect

🔋 Buffer Solution

📘 Definition

A solution whose pH does not change significantly even after adding small amounts of acid or base (amphiprotic buffer solution).

Resists change in pH
Important in biological systems (blood pH ≈ 7.4 maintained by buffer)
Used in medicine, food preservation, chemical labs

⚠️ Exam Trap — Colloid Applications

Blue colour of sky = Tyndall Effect (NOT reflection)
Delta formation at river mouth = coagulation of colloidal river silt by sea salt
Rain = charged clouds (colloids) attract dust particles → coagulate → rain
Blood is a colloid → FeCl₃ (ferric chloride) can stop bleeding (coagulation)

🥛 Emulsion

📘 Definition

A colloidal system made of two immiscible liquids (liquids that do not mix with each other, like oil and water).

💧 Oil in Water (O/W)

Oil droplets dispersed in water

Milk
Mayonnaise
Vanishing cream

🧈 Water in Oil (W/O)

Water droplets dispersed in oil

Butter
Cold Cream
Margarine

⚠️ Exam Trap — Emulsion Types

Milk = Oil in Water (O/W) emulsion (fat globules in water)
Butter = Water in Oil (W/O) emulsion (water droplets in fat)
Mayonnaise = O/W emulsion
Cold Cream = W/O emulsion
All emulsions are colloids (particle size 1–1000 nm)

🎯 High-Frequency BPSC/BSSC Exam Points

Solution = Homogeneous mixture; Solute (less) + Solvent (more)
Universal Solvent = Water (H₂O)
H₂ in Palladium = Gas in Solid solution
Mercury amalgam = Liquid in Solid solution
Air = Gas in Gas (gaseous solution)
Fog = Liquid in Gas | Smoke = Solid in Gas
Saturated: no more solute dissolves at given T & P
Temp ↑ → Saturated becomes Unsaturated
Temp ↓ → Unsaturated becomes Saturated
True solution particle: < 1 nm | Colloid: 1–1000 nm | Suspension: > 1000 nm
Tyndall Effect: Colloid ✓ + Suspension ✓ | True Solution ✗
Colloid separated by Centrifugation (e.g., Milk, Ink)
Suspension separated by Filtration (e.g., Chalk in water)
Colloid appears homogeneous but is actually heterogeneous
Blue colour of sky = Tyndall Effect
Delta formation = colloid coagulation at river-sea junction
Blood = colloid; FeCl₃ stops bleeding (coagulation)
Emulsion = colloidal system of immiscible liquids
Milk = Oil in Water (O/W) | Butter = Water in Oil (W/O)
Buffer solution = pH remains stable even on adding acid/base

📋 Quick Reference Table

Feature	Solution	Colloid	Suspension
Particle size	< 1 nm	1–1000 nm	> 1000 nm
Nature	Homogeneous	Pseudo-homogeneous	Heterogeneous
Tyndall Effect	No	Yes	Yes
Visible particles	No	No	Yes
Separation	Not by filtration	Centrifugation	Filtration
Examples	Sugar water	Milk, Ink, Blood	Chalk water

⚠️ Most Common Exam Traps

Colloid appears homogeneous but is heterogeneous
Tyndall Effect: NOT in true solution
Milk = Colloid (not true solution)
Milk = O/W emulsion; Butter = W/O emulsion
Colloid → Centrifugation; Suspension → Filtration
Temp ↑ → Saturated becomes Unsaturated (opposite intuition!)
Gas in liquid: solubility decreases with temp (opposite of solids)
Blue sky = Tyndall Effect (NOT because sky is blue inherently)
Delta = colloidal coagulation (charged particles neutralised by sea salt)

🧪 Solution & Colloid