C3.1.3 - Conservation of mass

Question 1

What is the law of conservation of mass?

Answer 1

The total mass stays the same during a chemical reaction, because atoms are not created or destroyed

Question 2

What is a closed system?

Answer 2

Apparatus in which substances cannot enter or leave the reaction mixture during a reaction

Question 3

What is a precipitate?

Answer 3

An insoluble product in the solid state, formed during a reaction involving solutions

Question 4

What is a non-enclosed system?

Answer 4

Apparatus in which substances can enter or leave the reaction mixture during a reaction

Question 5

What are examples of closed systems?

Answer 5

• a beaker of reactants in solution where the products are not gases
• a flask attached to a gas sharing to stop products in the gas state escaping

Question 6

What is an example of mass decreasing in a non-enclosed system?

Answer 6

Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen. As it is in gas state it escapes, so the mass appears to go down during the reaction

Question 7

What is an example of mass increasing in a non-enclosed system?

Answer 7

When metal reacts with oxygen in the air the metal atoms combine with oxygen atoms in the air