Water and Solubility Demonstrations

See also: Water Cycle, Fluids and Surface Tension

Water is often called the universal solvent because of its ability to dissolve many substances. This category looks at how solubility works, the factors that affect it, and why it is important in natural systems and daily life. Understanding solubility also provides insight into broader chemical ideas such as solutions and concentration.

Demonstration	Materials	Difficulty	Safety	Summary
Ammonia Fountain	★★★	★★★	★★★	Dry ammonia gas is collected in a sealed flask. When a small amount of water is injected, the ammonia rapidly dissolves, creating a partial vacuum that pulls water up into the flask. An indicator shows the resulting alkaline solution.
Borax Crystal Snowflakes	★★☆	★★☆	★★☆	Make snowflake ornaments from pipe cleaners by growing borax crystals from a hot, supersaturated solution. Compare color methods (colored pipe cleaners, food coloring, or post-painting with watercolors) and observe how crystals form and how color moves through the crystal structure.
Bubbling Lava Lamp	★☆☆	★☆☆	★☆☆	Two versions of a homemade lava lamp can be created using common household materials. In one, baking soda and vinegar react to produce bubbles that carry colored water through oil. In the other, antacid tablets release carbon dioxide bubbles that produce the same effect.
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.
Cleaning Water With Flocculation	★★☆	★★☆	★☆☆	Students clean real pond or river water using two flocculants, aluminum sulfate and a polymer clarifier. They compare how stirring and lowering pH with lemon juice affect how fast particles clump and settle.
Cooling Rate and Crystal Size	★★☆	★★☆	★★☆	This demonstration shows how the rate at which a saturated copper(II) sulfate solution cools affects the size of the crystals that form. When a hot saturated solution of copper sulfate is cooled slowly, large and well-defined blue crystals form. Rapid cooling produces many small, less regular crystals. The experiment illustrates how crystal size depends on the rate of nucleation and growth.
Copper Sulfate Crystals	★★☆	★☆☆	★★☆	A perfect seed crystal is grown in a shallow dish, then suspend the seed in a saturated, undisturbed solution so it enlarges slowly into a clear, well-formed single crystal. Careful control of saturation, evaporation, and disturbances is the key to size and quality.
Crystallization of Sodium Acetate	★★☆	★★☆	★★☆	A hot, concentrated solution of sodium acetate trihydrate is cooled quietly to create a supersaturated liquid. When poured onto seed crystals, it crystallizes instantly to build a warm, solid tower.
Effect of Particle Size on Solubility	★☆☆	★☆☆	★☆☆	This demonstration shows how the size of solid particles affects the rate at which they dissolve. By comparing the dissolving times of crushed and uncrushed table salt in water, students can observe that smaller particles dissolve faster due to greater surface area contact with the solvent.
Endothermic and Exothermic Dissolving	★★☆	★☆☆	★★☆	This demonstration compares two reactions: one that absorbs heat from the surroundings (endothermic) and one that releases heat (exothermic). Students can observe changes in temperature and feel whether the container becomes hot or cold.
Growing Alum Crystals	★★☆	★★☆	★☆☆	Potassium alum powder is dissolved in hot water to form a saturated solution that produces clear, diamond-shaped crystals as the solution cools and evaporates. By carefully selecting and growing a seed crystal, you can form large, pure alum crystals within one to two weeks.
Gummy Bear Osmosis	★★☆	★☆☆	★☆☆	This experiment demonstrates osmosis using gummy bears placed in different solutions such as water, salt water, sugar water, and baking soda water. Over 48 hours, students observe how water moves into or out of the gummy bears, changing their size and shape depending on the solution.
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.
How Salt Affects Freezing of Water	★☆☆	★☆☆	★☆☆	This demonstration compares how quickly plain water and saltwater freeze. By observing two bowls placed in a freezer, students discover that adding salt lowers the freezing point of water, making saltwater take longer to freeze.
Hydrophobic Coatings	★★☆	★☆☆	★☆☆	This demonstration shows how hydrophobic coatings prevent water from soaking into a surface. By applying a water-repellent spray to sand or using wax crayons on paper, students can see how water beads up and rolls off instead of being absorbed.
Ice Cube on a String	★☆☆	★☆☆	★☆☆	This simple experiment demonstrates how salt lowers the freezing point of water. By sprinkling salt on an ice cube and laying a string across it, the ice melts slightly and then refreezes, trapping the string so the ice cube can be lifted.
Instant Snow Polymer	★★★	★☆☆	★★☆	A small amount of instant snow polymer rapidly absorbs water and swells to many times its original volume, creating fluffy “snow and causing a temperature change.
Lead Iodide Precipitation	★★☆	★☆☆	★★☆	When aqueous lead(II) nitrate reacts with aqueous potassium iodide, a double displacement reaction occurs. Potassium nitrate remains dissolved, while lead(II) iodide precipitates as a bright yellow solid.
Magic Sand	★★★	★☆☆	★☆☆	Magic sand is ordinary sand coated with a hydrophobic substance that prevents it from mixing with water. When placed in water, it clumps together and forms shapes like towers or cakes, while remaining perfectly dry when removed.
Melting vs Dissolving	★☆☆	★☆☆	★★☆	Compare a phase change (melting) to forming a solution (dissolving) and use simple particle models to show how the particles behave differently in each case. Students melt common solids and then dissolve sugar in water to observe that dissolving is not melting.
Oil and Water Emulsification	★☆☆	★☆☆	★★☆	Oil and water normally separate into layers, but adding soap or detergent allows them to mix temporarily. This demonstrates how emulsifiers work by suspending oil droplets in water.
Rock Candy	★★☆	★★☆	★★☆	Dissolve sugar into hot water until it forms a supersaturated solution, then suspend sugar-coated sticks in jars to grow edible sugar crystals over several days. Color or flavor can be added to make decorative, tasty rock candy.
Salt Water Purifier	★☆☆	★☆☆	★☆☆	This experiment demonstrates how salt water can be turned into fresh water using evaporation and condensation. It models the natural water cycle, showing how solar energy drives evaporation, and how condensation can collect purified water, leaving the salt behind.
Soil Field Capacity	★★☆	★☆☆	★☆☆	Different soil types are tested for field capacity by adding water and measuring how much each soil retains after drainage, showing how soil properties affect water holding capacity.
Solubility of Salts	★☆☆	★☆☆	★☆☆	This experiment explores the solubility of different household compounds in water. By adding each compound gradually until no more dissolves, students discover the concept of saturation and compare how different substances dissolve in the same solvent.
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.
Temperature and Solubility of Salt vs. Sugar	★☆☆	★☆☆	★★☆	This demonstration compares how temperature affects the dissolving of sugar versus salt in hot and cold water. Students observe that sugar dissolves much more in hot water than in cold, while salt shows little difference.
Test for Hard Water	★☆☆	★☆☆	★☆☆	Use liquid soap and vigorous shaking in a clear, stoppered vessel to compare suds height and cloudiness in water samples. Soft water makes abundant stable foam; hard water forms little foam and turns cloudy as calcium/magnesium ions react with soap.
The Lost Volume Demonstration	★☆☆	★☆☆	★☆☆	Equal volumes of water and ethyl alcohol do not add up to their combined total volume when mixed. Instead, the mixture shows a reduced volume due to molecular interactions between water and alcohol.
Water on a Coin	★☆☆	★☆☆	★☆☆	Using an eyedropper, drops of water are placed on a coin and it's observed how many drops can pile up before spilling over. The activity demonstrates cohesion, adhesion, and surface tension in water compared with other liquids like oil and syrup.
‘Dissolving’ Styrofoam in Acetone	★★☆	★★☆	★★☆	When expanded polystyrene foam is placed in acetone (propanone), it appears to dissolve, dramatically shrinking in volume. This striking demonstration shows how acetone breaks down the foam structure by dissolving the polystyrene polymer, leaving only a small residue of solid polymer behind.

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