Conservation of Mass

Key Stage 3

Conservation of Mass is a law of the universe that states that mass cannot be created or destroyed, it can only be moved from one place to another.

In dissolving conservation of mass means that the mass of the solvent and the mass of the solute can be added to find the mass of the solution.


Mass_solvent + Mass_solute = Mass_solution

In a chemical reaction conservation of mass means that the same atoms which made up the reactants must make up the products. So the atoms are not created or destroyed in a chemical reaction, they are just rearranged.


Conservation of mass tells us that if there are 4 Hydrogen atoms and 2 Oxygen atoms at the start of this reaction then there will be the end of the reaction 4 Hydrogen atoms and 2 Oxygen atoms at the end of the reaction.


In this reaction you can see that mass is conserved because there are 4 Hydrogen atoms, 4 Oxygen atoms and 1 Carbon atom in the reactants and all the same atoms are found in the products.

Conservation of Mass is a law of the universe that states that mass cannot be created or destroyed, it can only be moved from one place to another.

In a chemical reaction law of conservation of mass indicates that the total mass of the products is the same as the total mass of the reactants.

Methane + Oxygen → Water + Carbon Dioxide

CH₄ + 2O₂ → 2H₂O + CO₂

16g + 64g = 36g + 44g

Sodium Hydroxide + Hydrochloric Acid → Sodium Chloride + Water

NaOH + HCl → NaCl + H₂O

40g + 36.5g = 58.5 + 18g

Find the mass of Calcium Oxide produced in the following reaction: CaCO₃ → CaO + CO₂ 25g = x + 11g	Find the mass of Carbon Dioxide produced in the following reaction: CH₄ + 2O₂ → 2H₂O + CO₂ 4g + 16g = 9g + x	Find the mass of Hydrochloric Acid needed in the following reaction: NaOH + HCl → NaCl + H₂O 160g + x = 234g + 72g
x = 25g - 11g x = 14g	20g = 9g + x x = 20g - 9g x = 11g	160g + x = 306g x = 306g - 160g x = 146g