Lesson: Conservation of Mass Chemistry • 7th Grade

In this lesson, we will learn how to use the law of conservation of mass to calculate the masses of reactants and products in a chemical reaction.

Lesson Plan

Students will be able to

describe the law of conservation of mass as applied to chemical reactions,
use the law of conservation of mass to calculate the mass of reactants or products in a chemical reaction,
identify the relationship between conservation of mass and the balancing of chemical equations,
identify why the total mass of the products may appear to change when performing experiments in an open system.

Lesson Video

Lesson Playlist

01:28
03:46

Lesson Worksheet

Q1:

Antoine Lavoisier was one of the first scientists to state the law of conservation of mass. When he heated a sample of tin and air in an airtight flask, tin reacted with oxygen in the air to produce tin oxide. Did the mass of the flask and its contents increase, decrease, or stay the same because of this reaction?

Q2:

A wet 43.2 g sample of copper sulfate heptahydrate is heated until only copper sulfate remains. The mass of the water lost is 34.1 g. What is the mass of the copper sulfate?

Q3:

A 13.5 g sample of calcium carbonate is heated until it decomposes completely and 7.6 g of calcium oxide is produced. What is the mass of carbon dioxide produced?