Lesson 1: Conservation of mass/ RFM

Question 1

What does The Law of The Conservation of mass?

Answer 1

The Law of The Conservation of Mass states that no atoms are lost/ made during chemical reactions so the mass of the products equals the mass of the reactants.

Question 2

What is the relative formula mass?

Answer 2

• The relative formula mass is the sum of the relative atomic masses of the atoms in the numbers shown in the formula.

Question 3

True or False

The sum of the relative formula masses of the reactants is higher than the sum of the relative formula masses of the products.

Answer 3

• False. The sum of the relative formula masses of reactants is equal to some of relative formula masses of products.

Question 4

Why do some chemical reactions appear to have a mass increase?
Give example.

Answer 4

Metal + oxygen –> Metal oxide
(metal oxide is heavier than the metal.)
As oxygen (in the air) wasn’t taken into account initially.

Question 5

Why do some chemical reactions appear to have a mass decrease?
Give an example.

Answer 5

• Thermal decomposition of metal carbonates forms carbon dioxide (escapes into atmosphere.)
• Metal oxide is only solid product and appears to be lighter.