Compounds Demonstrations

See also: Organic Chemistry

Compounds are substances formed when atoms of different elements join together in fixed proportions. This category introduces the idea of chemical bonding, the distinction between compounds and mixtures, and the unique properties compounds possess. Understanding compounds is a key step in explaining the diversity of substances found in nature and technology.

Demonstration	Materials	Difficulty	Safety	Summary
Carbon Sugar Snake	★★★	★★☆	★★★	A mixture of sugar and baking soda is ignited with lighter fluid on a sand base, producing an expanding black "snake" of carbon and sodium carbonate as gases from decomposition push the solid upward.
Electrolysis of Water	★★☆	★★☆	★★☆	An electric current is passed through a sodium sulfate or sulfuric acid solution, splitting water into hydrogen and oxygen gases. The gases are collected and tested—hydrogen ignites with a flame, while oxygen relights a glowing splint.
Floating and Sinking Grapes	★☆☆	★☆☆	★☆☆	This demonstration uses grapes in soda to show how surface properties affect buoyancy. An unpeeled grape floats to the top of a glass of soda, while a peeled grape sinks. The difference is due to CO₂ bubbles attaching to the grape skin, which changes the grape’s density relative to the liquid.
Golden Rain	★★☆	★★☆	★★☆	Lead nitrate reacts with potassium iodide to form a bright yellow precipitate of lead iodide. When heated, the precipitate dissolves in hot water, but as the solution cools, thin hexagonal crystals fall out of solution like golden flakes, creating the “golden rain” effect.
Ionic Cut and Match	★☆☆	★☆☆	★☆☆	Students cut out cards showing cations, anions, and compound formulas, then match them correctly. This reinforces naming rules and helps students practice writing and recognizing ionic compounds.
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.
Make Molecular Models	★★☆	★☆☆	★☆☆	Use a molecular model kit to make various chemical compounds.
Making Marshmallow Molecules	★☆☆	★☆☆	★☆☆	This activity uses colored marshmallows and toothpicks to model atoms, molecules, and compounds. By assembling marshmallows to represent different elements and connecting them with toothpicks as covalent bonds, students can visualize how atoms combine to form molecules and chemical structures.
Properties of Covalent, Ionic and Metallic Substances	★★☆	★★☆	★★☆	This experiment compares the physical properties of covalent, ionic, and metallic substances by observing their appearance, luster, solubility in water, melting point, and electrical conductivity. By analyzing differences, students can infer the type of bonding present in each substance.
Solid Lead Nitrate and Potassium Iodide	★★☆	★☆☆	★★☆	When lead nitrate and potassium iodide powders are combined and shaken, they undergo a double displacement reaction to produce yellow lead iodide.
Sugar and Sulfuric Acid Carbon Snake	★★☆	★★☆	★★☆	Concentrated sulfuric acid is added to sugar, causing a vigorous dehydration and oxidation reaction. The mixture heats up and produces steam, carbon dioxide, and a growing black column of carbon that resembles a snake rising from the container.
Thermal Decomposition of Ammonium Chloride	★★☆	★☆☆	★★☆	Ammonium chloride, when heated, undergoes decomposition into hydrogen chloride and ammonia gasses, before reforming when cool. The process appears similar to sublimation and deposition.
Thermal Decomposition of Copper Carbonate	★★☆	★★☆	★★☆	When copper carbonate is heated, it thermally decomposes to form copper oxide and carbon dioxide. The reaction is accompanied by a visible color change from green to black, and the gas produced can be confirmed as carbon dioxide by bubbling it through limewater, which turns cloudy.

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