Chemical Quantities and Calculations Demonstrations

See also: Measurement and Units

Chemical quantities and calculations provide the tools for predicting and measuring how substances interact. This category covers ideas such as balancing reactions, calculating amounts, and linking observable changes to underlying numbers. Mastering these concepts is essential for making sense of chemical change in both theory and practice.

Demonstration	Materials	Difficulty	Safety	Summary
Burning Steel Wool Increases Its Mass	★★☆	★★☆	★★☆	When steel wool is ignited, it reacts with oxygen in the air to form iron oxide. Surprisingly, the mass of the steel wool increases after burning because oxygen atoms from the air combine with the iron atoms.
Molecular Mass of Butane	★★☆	★★☆	★★☆	Butane from a lighter is collected in an inverted water-filled graduated cylinder. The mass of the lighter before and after gas release is used to find the gas mass. Using the ideal gas law, the number of moles of butane is determined and its molar mass is calculated.
Conservation of Mass with Baking Soda and Vinegar	★★☆	★☆☆	★☆☆	This experiment shows that matter is not created or destroyed in a chemical reaction. When baking soda reacts with vinegar, carbon dioxide gas inflates a balloon, and the total mass before and after the reaction remains nearly the same.
Enthalpy of Combustion of Alcohols	★★☆	★★☆	★★☆	A simple water calorimeter is used to measure the heat released when different alcohols burn. By tracking the water’s temperature rise and the mass of fuel consumed, students estimate the molar enthalpy of combustion and compare fuels.
Limiting Reactant	★☆☆	★★☆	★☆☆	Balloons filled with different amounts of baking soda are attached to flasks containing vinegar, producing varying amounts of carbon dioxide gas.
Molar Volume of Hydrogen	★★☆	★★☆	★★☆	Magnesium ribbon reacts with an acid to produce hydrogen gas, which is collected and measured. The measured volume can then be used to calculate the molar volume of a gas.
Performing a Titration	★★☆	★☆☆	★☆☆	A standard solution in a buret is added to an unknown solution in a flask until the reaction reaches its endpoint, signaled by an indicator color change (or pH jump). Initial and final buret readings are used to calculate the unknown molarity.
Stoichiometry in Combustion of Acetylene	★★★	★★★	★★★	Calcium carbide reacts with water to produce acetylene gas, which can be ignited to demonstrate combustion. By varying the ratio of acetylene to oxygen in test tubes, the experiment illustrates limiting reagents, incomplete vs. complete combustion, and stoichiometric balance.
Use of Volumetric Pipette	★★☆	★★☆	★☆☆	Correct technique for using a glass volumetric pipette.
Using a Burette	★★☆	★☆☆	★☆☆	A buret is a precise laboratory instrument used to deliver measured volumes of liquid. By reading the initial and final liquid levels, the exact volume dispensed can be calculated to a high degree of accuracy.
Using Volumetric Flasks	★★☆	★★☆	★☆☆	Volumetric flasks are precision glassware designed for preparing exact solution volumes, most often used for making dilutions and standard solutions. They allow accurate adjustment of a liquid to a single graduation mark, ensuring reliable concentrations for laboratory testing.
Visualizing the Mole	★★☆	★★☆	★☆☆	Students are shown weighed-out samples of different elements or compounds, each containing one mole of particles. This demonstration helps learners grasp the enormous scale of Avogadro’s number (6.022 × 10^23) by connecting it to tangible amounts of substances.

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