Mixtures and Separation Demonstrations

Mixtures are combinations of substances that can often be separated into their components. This category focuses on methods used to achieve separation, from simple physical techniques to more specialised approaches. Learning about mixtures and how to separate them provides a foundation for understanding both laboratory practice and natural processes.

Demonstration	Materials	Difficulty	Safety	Summary
Buchner Filtration	★★☆	★★☆	★★☆	Use a Buchner funnel and side-arm vacuum flask to separate a solid from a liquid quickly. The slurry is pulled through wetted filter paper by reduced pressure, leaving the solid on the paper for washing and drying.
Candy Chromatography	★☆☆	★☆☆	★☆☆	Paper chromatography is used to separate the dye mixture from colored candy coatings and compare the separated spots to known food colorings. Measure and compare Rf values to infer which approved food dyes are present.
DIY Centrifuge	★☆☆	★☆☆	★★☆	Centrifuges can be built using a variety of low cost methods. These range from hand-powered “paperfuge” whirligigs to salad-spinner and Dremel-driven rotors.
Electrostatic Smoke Precipitation	★★★	★★★	★★★	This demonstration models how an electrostatic smoke precipitator removes particulate matter (like smoke or ash) from the air using high voltage. Charged particles are attracted to oppositely charged plates and separated from the air stream, simulating industrial air purification systems used in power plants and factories.
Ester Synthesis, Isolation and Purification	★★☆	★★☆	★★☆	An alcohol reacts with a carboxylic acid under an acid catalyst to form an ester and water (Fischer esterification). An ester is synthesized under reflux, the organic layer isolated with a separatory funnel, dried, and purified by simple distillation.
Ethanol Purification by Distillation	★★☆	★★☆	★★☆	After fermenting a sugar solution with yeast, ethanol can be separated from the mixture using simple distillation. The distillate fractions collected can then be tested for ethanol content by carefully checking whether they ignite.
Evaporating Seawater	★☆☆	★★☆	★☆☆	Dissolve table salt in warm water to make a saturated solution, then leave the solution in a shallow container for days. As water evaporates, the remaining liquid becomes supersaturated and salt recrystallizes on the dish and along the waterline.
Fractional Distillation of Crude Oil	★★☆	★★☆	★★★	A crude oil sample is heated and liquid fractions are collected as temperature rises, modeling how refineries separate petroleum by boiling range.
Froth Flotation	★★☆	★☆☆	★☆☆	Students simulate the froth flotation process used in mining to separate valuable minerals from waste rock. By adding water, kerosene, and detergent to a mixture of sand and iron filings, they observe how bubbles can help separate materials.
Gravity Filtration	★★☆	★☆☆	★☆☆	Gravity filtration is a laboratory method used to separate a solid residue from a liquid filtrate by passing the mixture through filter paper held in a funnel. The technique allows suspended solids to be collected while the clear liquid passes through.
Homemade Water Purifier Model	★☆☆	★☆☆	★☆☆	Students build a simple water filter using a cut plastic bottle and layers of materials like sand, gravel, cotton, and activated charcoal. The experiment shows how filters remove impurities from dirty water, though the filtered water is not safe to drink.
Iron and Sulfur Compound Formation	★★☆	★★☆	★★☆	his demonstration shows the difference between a physical mixture and a chemical compound. Iron filings and sulfur powder can be mixed together and separated with a magnet, but when heated, they react to form iron sulfide, a compound that cannot be separated by physical means.
Leaf Chromatography	★★☆	★★☆	★★☆	Chromatography is used to separate pigments in green leaves. By dissolving leaf pigments in alcohol and drawing them up filter paper, students can see hidden colors like carotenoids and anthocyanins that are usually masked by chlorophyll.
Magnetic Separation of Sand and Iron Filings	★☆☆	★☆☆	★☆☆	Students mix sand and iron filings, then use a magnet to separate the iron filings from the sand. This demonstrates how differences in physical properties, like magnetism, can be used to separate mixtures.
Pen Ink Chromatography	★☆☆	★☆☆	★☆☆	Use simple paper chromatography to separate the color components in fountain pen inks. A small ink line on chromatography paper or paper towel is developed with water so the dissolved dyes travel different distances and reveal hidden color blends.
Ping Pong Ball Lipid Bilayer	★★☆	★★☆	★☆☆	This model demonstrates the fluid mosaic structure of the cell membrane using ping-pong balls, drinking straws, water, oil, and salt water. The arrangement represents a phospholipid bilayer with hydrophilic heads and hydrophobic tails, showing how the membrane behaves in an aqueous environment.
Solubility Rules	★★☆	★★☆	★★☆	Students systematically mix aqueous cations and anions in a well plate to observe when precipitates form, then use patterns in the results to draft practical solubility rules and write net ionic equations.
Strawberry DNA Extraction	★★☆	★★☆	★★☆	By crushing strawberries and treating them with detergent, salt, and alcohol, students can extract visible strands of DNA. The detergent breaks open the cells, salt keeps proteins separate, and alcohol causes DNA to clump so it can be seen with the naked eye.
Using a Separating Funnel	★★☆	★★☆	★★☆	Students learn how a separating (separatory) funnel is used to separate immiscible liquids by density and solubility differences. The demonstration covers correct setup, safe shaking and venting, identifying layers, draining/pouring layers, troubleshooting emulsions, and drying an organic layer.

Materials
★☆☆ Easy to get from supermarket or hardware store
★★☆ Available in most school laboratories or specialist stores
★★★ Requires materials not commonly found in school laboratories

Difficulty
★☆☆ Can be easily done by most teenagers
★★☆ Available in most school laboratories or specialist stores
★★★ Requires a more experienced teacher

Safety
★☆☆ Minimal safety procedures required
★★☆ Some safety precautions required to perform safely
★★★ Only to be attempted with adequate safety procedures and trained staff