Colloids | Types, Properties, Lyophilic & Lyophobic | Complete Guide

Colloids

Dispersion of microscopically insoluble particles – from milk to smoke, gels to foams

1. What are Colloids?

A colloid (or colloidal system) is a mixture in which one substance of microscopically dispersed insoluble particles (1–1000 nm) is suspended throughout another substance. The dispersed substance is called the dispersed phase, and the surrounding medium is the dispersion medium. Colloids are distinct from true solutions (solute < 1 nm) and suspensions (> 1000 nm).

Particle size range: 1 nm to 1000 nm (1 × 10⁻⁹ m to 1 × 10⁻⁶ m)

Colloids exhibit the Tyndall effect – scattering of light by the dispersed particles, which makes the beam visible from the side. They are generally stable and do not settle on standing.

2. Tyndall Effect Simulation

When a beam of light passes through a colloid, it is scattered by the particles – this is the Tyndall effect. In a true solution, the beam is invisible. The simulation below shows a laser beam passing through a colloidal solution (left) vs. a true solution (right). The animation continuously highlights the scattering.

Left: Colloid – light beam is scattered (visible). Right: True solution – no scattering.

3. Classification of Colloids

3.1 Based on Nature of Interaction

Hydrophilic (Lyophilic) Colloids
Water-loving. Form reversible sols. Examples: gelatin, starch, agar.

Hydrophobic (Lyophobic) Colloids
Water-repelling. Irreversible sols. Examples: gold sol, clay particles.

3.2 Based on Type of Particles

Multimolecular Colloids
Aggregates of many atoms/small molecules (size < 1 nm) held by van der Waals forces. Example: gold sol, sulphur sol.

Macromolecular Colloids
Large molecules (polymers) of colloidal size. Example: starch, proteins, synthetic polymers.

Associated Colloids (Micelles)
Electrolytes that form micelles above CMC (Critical Micelle Concentration). Example: soaps, detergents.

3.3 Based on Physical State of Phases

Foam
Gas dispersed in liquid – whipped cream, shaving cream.

Emulsion
Liquid dispersed in liquid – milk, mayonnaise.

Sol
Solid dispersed in liquid – blood, pigmented ink.

Aerosol
Liquid or solid dispersed in gas – fog, smoke, spray.

Gel
Liquid dispersed in solid – agar, gelatin, jelly.

Solid Foam
Gas dispersed in solid – styrofoam, pumice.

4. Lyophilic vs. Lyophobic Sols

These two classes differ significantly in preparation, stability, and properties.

Property	Lyophilic (solvent-loving)	Lyophobic (solvent-hating)
Ease of preparation	Direct mixing with solvent	Requires special methods (e.g., Bredig’s arc method, chemical reduction)
Charge on particles	Little or no charge	Carry positive or negative charge (stabilized by charge)
Solvation	Particles are solvated (surrounded by solvent layer)	No solvation, no protective layer
Viscosity	Higher than medium; can form gels	Almost same as medium
Precipitation (coagulation)	Requires high electrolyte concentration	Coagulated by low electrolyte concentration
Reversibility	Reversible – can be reconstituted after drying	Irreversible – once coagulated, cannot be reformed
Tyndall effect	Weak or no Tyndall effect	Strong Tyndall effect
Electrophoresis	May migrate to either electrode or not at all	Move to anode or cathode depending on charge

Example of lyophilic: gelatin, starch. Example of lyophobic: gold sol, ferric hydroxide sol.

5. Properties of Colloids

Tyndall effect: Scattering of light – colloidal particles scatter light, making the beam visible.
Brownian motion: Continuous random motion of colloidal particles due to bombardment by solvent molecules.
Coagulation: The process of destabilizing a colloid to cause aggregation and precipitation, usually by adding electrolytes.
Electrophoresis: Movement of charged colloidal particles under an electric field – used to determine charge.
Dialysis: Removal of electrolytes from a colloid using a semipermeable membrane.

Hardy–Schulze rule: The coagulating power of an ion increases with its valency.

6. Applications of Colloids

Food
Milk (fat in water), butter (water in fat), ice cream, jelly, mayonnaise.

Medicine & Pharmacy
Colloidal silver (antiseptic), ointments, vaccines, drug delivery systems.

Industrial
Paints, inks, lubricants, photographic films, rubber latex.

Environmental
Wastewater treatment (coagulation), air purification (aerosols).

Personal Care
Shampoos, creams, lotions, toothpaste.

7. Video Lecture: Colloids (Urdu/Hindi)

Watch Complete Lecture in Urdu/Hindi for Comprehensive Understanding

Detailed explanation of colloids, classification, lyophilic/lyophobic, Tyndall effect, and applications.

8. Summary

Colloids are heterogeneous mixtures with particle size 1–1000 nm.
They exhibit Tyndall effect, Brownian motion, and electrophoresis.
Lyophilic colloids are solvent-loving, reversible, and form gels; lyophobic colloids are solvent-hating, irreversible, and require stabilisation.
Colloids are classified based on interaction, particle type, and physical states (foams, emulsions, sols, gels, aerosols).
Applications span food, medicine, industry, and environmental science.

Critical Micelle Concentration (CMC): concentration at which micelles form in associated colloids.

/* ========== MAIN CONTINUOUS COLLOIDS SIMULATION ========== */ (() => { const canvas = document.getElementById(‘colloidSim’); if (!canvas) return; const ctx = canvas.getContext(‘2d’); const W = canvas.width; const H = canvas.height;// Stages: 0 True solution → 1 Colloid+Tyndall → 2 Coagulating → 3 Settling → loop const STAGE_DUR = [5.2, 7.0, 5.0, 6.2]; let stage = 0, stageTime = 0, last = 0; let particles = [], beams = [], clusters = [], floatMarks = []; const beam = { x: 28, y: H * 0.40, w: W – 56, h: 58 };class P { constructor() { this.x = 40 + Math.random() * (W – 80); this.y = 30 + Math.random() * (H – 80); this.baseR = 3.0 + Math.random() * 4.5; this.r = this.baseR; this.vx = (Math.random() – 0.5) * 1.0; this.vy = (Math.random() – 0.5) * 1.0; this.hue = 195 + Math.random() * 45; this.a = 0.8; this.settled = false; this.mass = this.baseR * 0.45; } color(al) { return `hsla(${this.hue}, 85%, 58%, ${al ?? this.a})`; } step(dt, st) { if (this.settled) return; if (st === 0) { this.r = this.baseR * 0.22; this.a = 0.10; } else if (st === 1) { this.r = this.baseR; this.a = 0.82; } else { this.r = this.baseR * 1.05; this.a = 0.85; }const kick = st === 0 ? 0.55 : st === 1 ? 0.36 : 0.15; this.vx += (Math.random() – 0.5) * kick; this.vy += (Math.random() – 0.5) * kick;if (st >= 2) { this.vy += 0.055 * this.mass; this.vx *= 0.965; this.vy *= 0.98; } else { this.vx *= 0.987; this.vy *= 0.987; }const maxS = st >= 2 ? 2.5 : 1.7; const s = Math.hypot(this.vx, this.vy); if (s > maxS) { this.vx = this.vx/s*maxS; this.vy = this.vy/s*maxS; }this.x += this.vx; this.y += this.vy;if (this.x W-this.r-5) { this.x = W-this.r-5; this.vx *= -0.5; } if (this.y H – this.r – 7) { this.y = H – this.r – 7; this.vy *= -0.12; this.vx *= 0.8; if (st === 3) { if (Math.abs(this.vy) < 0.4) { if (Math.abs(this.vx) < 0.45) { this.settled = true; this.vx = 0; this.vy = 0; if (Math.random() = 2) { if (!this.settled) { for (const o of particles) { if (o === this) continue; if (o.settled) continue; const dx = o.x-this.x, dy = o.y-this.y, d = Math.hypot(dx,dy); if (d 0.5) { const f = 0.1 / (d * 0.13); this.vx += (dx/d)*f; this.vy += (dy/d)*f; } } } } } } draw() { if (this.a < 0.04) return; ctx.save(); ctx.beginPath(); ctx.arc(this.x, this.y, this.r + (this.settled ? 1.5 : 3.5), 0, Math.PI*2); ctx.fillStyle = this.color(this.settled ? 0.1 : 0.18); ctx.fill(); ctx.beginPath(); ctx.arc(this.x, this.y, this.r, 0, Math.PI*2); const g = ctx.createRadialGradient(this.x-this.r*0.3, this.y-this.r*0.3, 0.4, this.x, this.y, this.r); g.addColorStop(0, `hsla(${this.hue},90%,78%,${this.a})`); g.addColorStop(1, this.color()); ctx.fillStyle = g; ctx.fill(); ctx.restore(); } }function resetParticles() { particles = []; clusters = []; beams = []; for (let i = 0; i { p.settled = false; p.vx = (Math.random()-0.5)*1.2; p.vy = (Math.random()-0.5)*1.2; }); addFloat(‘True solution’, ‘#8a9bb5’); } else if (s === 1) addFloat(‘Colloid · Tyndall effect’, ‘#00b4ff’); else if (s === 2) addFloat(‘Coagulation starts’, ‘#ff6b6b’); else if (s === 3) addFloat(‘Settling’, ‘#7b5cff’); }function update(dt) { stageTime += dt; if (stageTime >= STAGE_DUR[stage]) { const next = (stage + 1) % 4; if (next === 0) resetParticles(); setStage(next); } particles.forEach(p => p.step(dt, stage));const scatterRate = stage === 1 ? 0.16 : (stage === 2 ? 0.05 : 0); if (scatterRate > 0) { particles.forEach(p => { if (p.settled || p.a beam.y-5) { if (p.y beam.x) { if (p.x < beam.x+beam.w) { if (Math.random() { b.life -= dt; b.r += 10*dt; }); beams = beams.filter(b => b.life > 0); clusters.forEach(c => { c.r += 3.5*dt; c.life -= dt*0.4; }); clusters = clusters.filter(c => c.life > 0); floatMarks.forEach(f => { f.life -= dt; f.y -= 8*dt; }); floatMarks = floatMarks.filter(f => f.life > 0); if (stage <= 1) { if (particles.length < 110) { if (Math.random() { ctx.beginPath(); ctx.arc(b.x,b.y,b.r,0,Math.PI*2); ctx.fillStyle = `hsla(${b.hue},95%,72%,${b.life*0.75})`; ctx.fill(); ctx.beginPath(); ctx.arc(b.x,b.y,b.r*0.35,0,Math.PI*2); ctx.fillStyle = `rgba(255,255,240,${b.life*0.5})`; ctx.fill(); }); }if (stage === 3) { ctx.fillStyle = ‘rgba(80,120,160,0.08)’; ctx.beginPath(); ctx.moveTo(0,H); ctx.lineTo(0,H-18); for (let x=0; x !p.settled).forEach(p => p.draw()); particles.filter(p => p.settled).forEach(p => p.draw()); clusters.forEach(c => { ctx.beginPath(); ctx.arc(c.x,c.y,c.r,0,Math.PI*2); ctx.fillStyle = `hsla(${c.hue},70%,52%,${c.life*0.28})`; ctx.fill(); });floatMarks.forEach(f => { ctx.save(); ctx.globalAlpha = Math.min(1, f.life*0.85); ctx.font = ‘600 15px system-ui,sans-serif’; ctx.textAlign = ‘center’; const tw = ctx.measureText(f.text).width, x = W/2; ctx.beginPath(); roundRect(ctx, x-tw/2-14, f.y-12, tw+28, 26, 13); ctx.fillStyle = ‘rgba(255,255,255,0.93)’; ctx.fill(); ctx.strokeStyle = f.col; ctx.lineWidth = 1.6; ctx.stroke(); ctx.fillStyle = f.col; ctx.textBaseline = ‘middle’; ctx.fillText(f.text, x, f.y+1); ctx.restore(); });// progress dots const startX = W/2 – 42; for (let i=0; i { const canvas = document.getElementById(‘tyndallCanvas’); if (!canvas) return; const ctx = canvas.getContext(‘2d’); const width = 700, height = 300; canvas.width = width; canvas.height = height; let scatteringIntensity = 0.2, direction = 1;function drawTyndall(intensity) { ctx.clearRect(0,0,width,height); ctx.fillStyle = “#1a2a32”; ctx.fillRect(0,0,width,height); ctx.fillStyle = “rgba(255,255,255,0.1)”; ctx.fillRect(50,50,250,200); ctx.fillRect(400,50,250,200); ctx.strokeStyle = “#ffffff”; ctx.lineWidth = 1.5; ctx.strokeRect(50,50,250,200); ctx.strokeRect(400,50,250,200); ctx.fillStyle = “#ffffff”; ctx.font = “14px system-ui”; ctx.fillText(“Colloidal Solution”, 100, 40); ctx.fillText(“True Solution”, 450, 40); ctx.beginPath(); ctx.moveTo(20,150); ctx.lineTo(50,150); ctx.strokeStyle = “#ff4444”; ctx.lineWidth = 3; ctx.stroke(); ctx.fillStyle = “#ff4444”; ctx.fillText(“Laser”, 5, 145); ctx.beginPath(); ctx.moveTo(50,150); ctx.lineTo(300,150); ctx.strokeStyle = “#ff8888”; ctx.lineWidth = 2; ctx.stroke(); if (intensity > 0.05) { ctx.globalAlpha = Math.min(0.8, intensity); for (let i=0; i= 1) { scatteringIntensity = 1; direction = -1; } else if (scatteringIntensity { direction = 1; scatteringIntensity = 0.2; drawTyndall(scatteringIntensity); }); })();

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Colloids

1. What are Colloids?

2. Tyndall Effect Simulation