This chemistry class lesson introduces the concepts of oxidation and reduction reactions. It defines oxidizing and reducing agents and explains how to identify them in chemical equations. Examples are provided of assigning oxidation numbers and representing electron transfer processes. The lesson also demonstrates tests for identifying the presence of oxidizing and reducing agents in solutions. Practice problems are included for students to determine oxidizing and reducing agents in example reactions.

1. Welcome to
Chemistry class!
Learning objectives

2. Duration: 45 min Secondary School Grades: 8 IGCSE
Oxidizing & reducing
agents
Science – Grade 8
By Ms.Ngan

3. 1. Key contents
- Oxidation number of C increases from 0 to +4
 C is the reducing agent.
- Oxidation number of O decreases from 0 to -2
 O2 is the oxidizing agent.
Assign the oxidation number of all elements in the
reaction: C + O2  CO2
Is this reaction a redox reaction?

4. 1. Key contents
In a redox reaction:
- Oxidizing agent is the substance having the decrease in oxidation
number (gaining electrons). Oxidizing agent is reduced.
- Reducing agent is the substance having the increase in oxidation
number (losing electrons). Reducing agent is oxidized.

5. 1. Key contents
- C loses 4 electrons: C0 – 4e  C4+
 Losing electrons is the oxidizing process
- Each O gains 2 electrons: O + 2e  O2-
 O2 + 2x2e  2O2-
 Gaining electrons is the reducing process
How to represent the gaining/losing electrons process in
the reaction: C + O2  CO2

6. 1. Key contents

7. 1. Key contents
Determine the oxidizing and reducing agents in the
reaction: 2Mg + O2  2MgO
Then represent the oxidizing and reducing processes.
Oxidizing agent: O2 Reducing agent: Mg
Reducing process: O2 + 2x2e  2O2- Oxidizing process: Mg - 2e  Mg2+

8. 1. Key contents
Determine the oxidizing and reducing agents in the
reaction: 2Al + O2  2Al2O3
Then represent the oxidizing and reducing processes.
Oxidizing agent: Reducing agent:
Reducing process: Oxidizing process:
O2 Al
Al0 – 3e  Al3+
O2 + 2x2e  2O2-

9. 1. Key contents
Determine the oxidized and reduced agents in the
reaction: 2Fe + O2  2FeO
Reducing agent = oxidized agent  Fe
Oxidizing agent = reduced agent  O2

10. 1. Key contents
Determine the oxidizing and reducing agents in the
reaction: Fe + 2HCl  FeCl2 + H2
- Oxidation number of Fe increases from 0 to +2
 Fe is the reducing agent.
- Oxidation number of H2 decreases from +1 to 0
 H+ (HCl) is the oxidizing agent.

11. 1. Key contents
Determine the oxidizing and reducing agents in the following reactions:
a. Mg + 2HCl  MgCl2 + H2
b. Zn + H2SO4  ZnSO4 + H2
c. CuO + CO  Cu + CO2
d. Mg + CuSO4  MgSO4 + Cu

12. 1. Key contents

13. 1. Key contents
Test for an oxidizing agent
Use aqueous KI solution
to test for the presence of
an oxidizing agent.
Result: solution turns to
brown color.

14. 1. Key contents
Test for an reducing agent
Use acidified KMnO4
solution to test for the
presence of an reducing
agent.
Result: solution changes
from purple to colorless.

15. 2. Practice
Ex1:
Ex2:

16. 2. Practice
Ex3:

17. 2. Practice
Ex4:

18. 2. Practice
Ex5:

19. 2. Practice
Ex6:

20. Thanks for using Lifeliqe's lesson plan!
Excite your students in learning science with 1,000+ more 3D models and lesson plans at online.lifeliqe.com