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)
Aerosol (heterogeneous)	Liquid	Gas	Fog: liquid droplets in gas; an aerosol, not a true solution
Aerosol (heterogeneous)	Solid	Gas	Smoke: fine solid particles in gas; an aerosol, not a true solution

⚠️ 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
If that solute’s solubility rises with temperature, heating can make it unsaturated

Unsaturated Solution

More solute can still dissolve

At given T and P, more solute can still be added
Cooling can lead to saturation if solubility decreases enough
Example: 30g NaCl + 100 ml H₂O = Unsaturated

📘 Temperature Effect on Solubility

For a solid solute with increasing solubility on heating: a saturated solution can become unsaturated
Cooling may cause saturation or crystallisation when the solubility limit falls sufficiently
Most solids: solubility increases with temperature
Gases in liquid: solubility decreases with temperature (carbonated drinks go flat when warm)

⚠️ Exam Trap

For solutes whose solubility rises with temperature, heating a saturated solution can make it unsaturated
Cooling can produce saturation if the lower-temperature solubility limit is reached
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)
Water treatment: alum coagulates colloidal impurities

Natural Applications

Rain formation — clouds are colloids
Clear blue sky: molecular Rayleigh 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
Clear sky is blue primarily due to molecular Rayleigh scattering, not colloidal Tyndall scattering
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 (within its finite buffer capacity).

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

Clear blue sky: molecular Rayleigh scattering; fog/dust beams: scattering by dispersed particles
Delta formation at river mouth = coagulation of colloidal river silt by sea salt
Water vapour condenses on aerosol nuclei; droplets/ice particles grow through processes that can lead to rain
Blood is a complex dispersed system; alum coagulation is a standard water-treatment example

🥛 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
An emulsion disperses droplets of one liquid in another immiscible liquid

🎯 High-Yield 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
For increasing solid-solute solubility, heating can make a saturated solution unsaturated
Cooling may reach saturation; it is not automatic for every solution
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
Clear blue sky: molecular Rayleigh scattering
Delta formation = colloid coagulation at river-sea junction
Blood contains colloidal proteins and suspended cells; alum is used to coagulate impurities in water
Emulsion = colloidal system of immiscible liquids
Milk = Oil in Water (O/W) | Butter = Water in Oil (W/O)
A buffer resists large pH changes from small additions of acid/base within its buffer capacity

📋 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
Temperature effects depend on the solute; many solids become more soluble on heating, gases generally less soluble
Gas in liquid: solubility decreases with temp (opposite of solids)
Clear blue sky: molecular Rayleigh scattering
Delta = colloidal coagulation (charged particles neutralised by sea salt)

🧪 Solution & Colloid