Learning objectives

Students will be able to demonstrate that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products.

Real world application

The law of conservation of mass will help you explain that while a chemical reaction, such as rusting, may appear to cause an increase in mass, the change is due to the mass of the gas reacting with the metal.

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Drag the empty flask or beaker onto the balance to measure its mass. Click the buttons to select amounts of MnS(s) and HCl(aq). Drag the filled flask or beaker onto the balance to measure its new mass.
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MnS(s) + 2HCl(aq) → MnCl2(aq) + H2S(g)

0.0000 g

MnS(s)


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HCl(aq)


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