What is CSEEL and what does it offer?

CSEEL (Center for Scientific Exploration and Experiential Learning) is a premier Indian STEM educational initiative offering hands-on science experiments, 3D live laboratory simulations, curriculum-aligned project kits, teacher training workshops, and national science conclaves aligned with NEP 2020.

How does CSEEL support NEP 2020 experiential learning?

CSEEL shifts education from rote memorization to active inquiry and hands-on experimentation. Students observe, build, analyze, and apply scientific concepts to real-world challenges, developing critical thinking and scientific temper as envisioned by NEP 2020.

What subjects and classes are covered in CSEEL simulations and experiments?

CSEEL provides comprehensive physics, chemistry, biology, environmental science, and applied robotics experiments and virtual simulations for students from Class 6 through Class 12, mapped to CBSE, ICSE, and state curricula.

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Preparation of Colloidal Sol & Tyndall Effect Demonstration

Experiment video

What you will learn

Prepare a lyophilic starch sol and a lyophobic Ferric Hydroxide [Fe(OH)3] sol, and demonstrate light scattering (Tyndall Effect) using a red laser beam.

Materials needed

Ferric Chloride (FeCl3) 2% w/v solution mL
Ferric Chloride (FeCl3) 2% w/v solution mL
₹50
What is it?
Anhydrous / Hexahydrate Iron(III) Chloride (FeCl3·6H2O) AR analytical crystals.
Specifications
Purity
≥ 99.0% AR grade
Iron Content
Approx 20% Fe
State
Brownish-yellow deliquescent lumps
Solubility
Freely soluble in water
Soluble Starch Powder g
Soluble Starch Powder g
₹95
What is it?
Red 650 nm collimated diode laser pointer for optical scattering analysis.
Specifications
Wavelength
650 nm (Visible Red)
Output Power
< 5 mW Class 3R laser
Beam Divergence
< 1.5 mrad
Power Source
2 × AAA alkaline cells
Sodium Chloride (NaCl) crystals g
Sodium Chloride (NaCl) crystals g
₹140
What is it?
Dialysis tubing membrane (regenerated cellulose) with sealing clamps.
Specifications
Membrane Material
Regenerated cellulose membrane
Pore Molecular Cutoff
12,000 – 14,000 Daltons
Flat Width
32 mm
Length
1.0 meter
Red Semiconductor Laser Pointer (650 nm)
Red Semiconductor Laser Pointer (650 nm)
₹185
What is it?
Standard laboratory apparatus used in Preparation of Colloidal Sol & Tyndall Effect Demonstration.
Specifications
Category
Chemistry Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Boiling Beakers (250 mL and 500 mL)
Boiling Beakers (250 mL and 500 mL)
₹230
What is it?
Standard laboratory apparatus used in Preparation of Colloidal Sol & Tyndall Effect Demonstration.
Specifications
Category
Chemistry Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Bunsen Burner, Tripod stand, and Wire Gauze set
Bunsen Burner, Tripod stand, and Wire Gauze set
₹275
What is it?
Standard laboratory apparatus used in Preparation of Colloidal Sol & Tyndall Effect Demonstration.
Specifications
Category
Chemistry Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Glass Rod and Dropper Pipette
Glass Rod and Dropper Pipette
₹320
What is it?
Standard laboratory apparatus used in Preparation of Colloidal Sol & Tyndall Effect Demonstration.
Specifications
Category
Chemistry Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard

Tick items as you collect them. Tap + to see the product, specifications and buy options.

Stay safe

Distilled water must be boiling vigorously when adding FeCl3 dropwise to prevent coarse precipitation.
Never point the laser beam towards anyone's eyes.
Apparatus must be scrupulously clean; electrolyte traces can coagulate lyophobic sols.
Starch paste must be lump-free before addition to boiling water.

Steps

0 of 6 steps done

1Preparation of Starch Sol (Lyophilic): Make a smooth paste of 1 g starch in 10 mL cold water. Pour this paste slowly with vigorous stirring into 100 mL boiling distilled water. Boil for 2 minutes and cool.
Observation
Clean 250 mL conical flask by steaming out thoroughly with distilled water to remove ionic impurities.
Safety
Wear heat-resistant gloves while handling boiling glassware.
2Preparation of Fe(OH)3 Sol (Lyophobic): Boil 100 mL distilled water in a beaker. Add 2% FeCl3 solution drop by drop using a dropper while boiling continuously.
Observation
Boil 100 mL of double distilled water vigorously on wire gauze using Bunsen burner.
Safety
Support beaker securely on heavy tripod stand with ceramic center wire gauze.
3A deep wine-red/brown colloidal sol forms via hydrolysis: FeCl3 + 3 H2O -> Fe(OH)3(sol) + 3 HCl.
Observation
Add 2% Ferric Chloride (FeCl3) solution drop-by-drop using a dropper while boiling continuously.
Safety
Add FeCl3 slowly (1 drop per 2 seconds); rapid addition causes brown precipitate instead of sol.
4Prepare a true solution of NaCl in 100 mL water as a control comparison.
Observation
Solution transforms from yellow to brilliant clear deep wine-red Fe(OH)3 colloidal sol.
Safety
Continue boiling for only 2-3 minutes after last drop; excessive boiling causes coagulation.
5Darken the room. Pass the red laser beam horizontally through: (1) True NaCl solution, (2) Starch sol, (3) Fe(OH)3 sol.
Observation
Cool to room temperature; shine 650 nm red laser pointer through sol alongside NaCl true solution.
Safety
Never shine laser pointer directly into eyes or at reflective mirrored surfaces.
6Observe that the laser path is invisible in true solution, but produces a brilliant illuminated optical cone (Tyndall Effect) in the colloidal sols.
Observation
Laser beam creates brilliant glowing illuminated track in Fe(OH)3 sol, while remaining invisible in NaCl.
Safety
Pour sol through parchment paper dialysis bag to remove excess HCl electrolyte.

Tap + on a step to see what you will observe and any safety tips.

Record your observations

Optical / Physical Test	True Solution (0.1M NaCl)	Colloidal Sol (Fe(OH)3 Sol)	Suspension (Chalk in Water)
Laser Beam Path (Tyndall Effect)	Invisible / Dark (No scattering)	Brilliant luminous laser beam path illuminated	Scattered & blocked rapidly (Opaque)
Appearance in White Light	Crystal clear, completely transparent	Translucent deep wine-red / reddish-brown	Turbid, milky white suspension
Filterability (Whatman Paper)	Passes through completely without residue	Passes through filter paper without residue	Retained on filter paper as solid residue
Stability after 24 hours	Completely stable, no settling	Completely stable, no coagulation or sediment	Particles settle out completely by gravity

Tap a highlighted cell to write your own observation.

Result and conclusion

Stable wine-red Ferric Hydroxide sol and translucent starch sol prepared. Red laser beam exhibits clear brilliant Tyndall cone through both sols while remaining invisible in true aqueous NaCl solution.

FeCl3 + 3 H2O (Boiling) -> Fe(OH)3 (Hydrated Ferric Hydroxide Sol - Positive Charge) + 3 HCl

Observation	What it means
Colloidal Particle Size Range	Sol particles lie in 1 to 100 nm colloidal range, larger than solvent molecules but small enough to remain suspended by Brownian motion.
Tyndall Light Scattering	Colloidal particles have dimensions comparable to visible laser wavelength (λ = 650 nm), scattering photons laterally (Tyndall cone).
Positive Sol Charge Stability	Fe(OH)3 particles preferentially adsorb Fe³⁺ ions from solution, acquiring positive electrical charge preventing coagulation.
True Solution Comparison	NaCl ions are < 1 nm in size; they do not scatter laser light, leaving the beam path completely invisible inside the liquid.

Scattered Light Intensity (Tyndall Effect) vs Dispersed Particle Diameter

Sample readings. Replace with your own results.

Experiment photos

Before the experimentDuring the experimentResult