1. Week 10, Lesson 2 – Chemistry Revision
Conservation of mass with lead iodide

2. Conservation of Mass
WALT: Explain what ‘conservation of mass’ means and relate this to an experiment
I must be able to state what ‘conservation of mass’ means in chemistry
I should be able to carry out a practical to demonstrate this and explain what it shows
I could explain this in terms of particle theory

3. This week, we have looked at gas tests…
Spend 2 minutes testing your neighbour on how we test for the different gases. Swap after 1 minute.

4. Let’s turn to page 223 of the red books
We will read through the paragraph together What does ‘conservation of mass’ mean? Conservation of mass means that the mass of the products after an experiment is equal to the mass of the reactants that went into the experiment In other words – no atoms are lost – what comes out of an experiment must weigh what goes in

5. Can you think of an experiment with magnesium that demonstrates conservation of mass?

6. We are going to react potassium iodide with lead nitrate
Write down a diagram, method and conclusion
In your conclusion – answer these questions:
How did you know that a reaction had taken place?
How does your experiment demonstrate conservation of mass?
Describe how the experiment with magnesium also demonstrates conservation of mass.

7. Chemistry (green Harriss and Ferguson books)
Answer questions 1-7 on page 64 (all parts) in full sentences and for prep (see photocopy)
(MBA questions on next slide)

8. MBA questions
1) When 127 g of copper reacts with 32 g of oxygen gas to form copper (II) oxide, no copper or oxygen is left over. How much copper (II) oxide is produced?
F 32 g
G 95 g
H 127 g
J 159 g
2) The mass of a rusty bicycle is found to be slightly greater than the mass of the same bicycle before it rusted. The change in mass indicates that the rusting process —
A is a physical change
B involves an energy-to-matter conversion
C decreases the density of the metal
D involves metal bonding with other atoms
Answers – J and D

9. Plenary
In pairs, discuss and agree what this reaction showed in no more than two spoken sentences.
Review each other’s answers to the questions.