Conservation of Mass and the Laws of Chemical Combination – Open and Closed Systems

What it shows

This virtual lab follows the laws of chemical combination with real balance readings. On the first bench, magnesium burns in a crucible or a sealed flask, marble chips react with hydrochloric acid in an open or capped bottle, and two solutions form a barium sulfate precipitate: the reading changes only when a gas enters or leaves. The second bench weighs magnesium oxide, copper(I) sulfide and the two copper oxides to show definite and multiple proportions. The third reacts gas volumes at the same temperature and pressure, explained by Avogadro's law.

How to use

Choose a tab. On Conservation of mass, pick a Reaction and an Open or Closed system, set the mass and press Start experiment. On Mass ratios, pick the Experiment and masses, then read the three or four balance readings in the table. On Gas volumes, set the two volumes, press Start experiment and try to leave no gas over.

Parameters you can change

• Screen Conservation of mass, Mass ratios, Gas volumes
• Reaction Burning magnesium (Mg + O₂), Marble chips + hydrochloric acid (CaCO₃ + HCl), Precipitation (BaCl₂ + Na₂SO₄)
• System Open system, Closed system
• Mass of solid 0.1–2 g
• Mass ratio experiment Heating magnesium in air → MgO, Heating copper with sulfur → Cu₂S, Reducing copper oxide with H₂ (CuO, Cu₂O)
• Reaction between gases Hydrogen + oxygen → steam (120 °C), Hydrogen + chlorine → hydrogen chloride
• Volume of H₂ 0–100 cm³
• Volume of the second gas 0–100 cm³

Questions to explore

1. Why does the balance reading rise when magnesium burns in an open crucible but not in a sealed flask?
2. Why is the mass ratio of magnesium to oxygen the same for every mass of magnesium?
3. What volume of oxygen reacts exactly with 60 cm³ of hydrogen at the same temperature and pressure?