Conservation of mass

Question 1

What is the rule of conversation of mass

Answer 1

During a chemical reaction no atoms are destroyed and no atoms are created. This means there are the same number and types of atoms on each side of the reaction equation.

Question 2

Why would mass seem to change

Answer 2

Because a gas is involved

Question 3

In some experiments you might observe a change of mass.

Explain why

Answer 3

Because the reactions vessel is unsealed

Question 4

what happens when mass increases

Answer 4

-If the mass increases, it’s probably because at least one of the reactants is a gas that’s found in air and the products are solid, liquid or aqueous

• Before the reaction, the gas is floating around in the air. It’s there, but it’s not contained in the reaction vessel so you cannot account for its mass
• When the gas reacts to form part of the product, it becomes contained in the vessel
• So mass inside increases

Question 5

What happens when mass decreases

Answer 5

-If mass decreases, it’s probably because some, or all, of the reactants are solids, liquids or aqueous reactants and at least one of the products are a gas.

• Before the reaction the reactants are contained in the reactions vessel
• If the vessel isn’t enclosed then the gas can escape from the reactions vessel. It’s no longer contained in the reaction vessel, so you can’t account for its mass
• so the total mass of the stuff inside the vessel decreases