1. Chemistry 20.1

2. The Meaning of Oxidation and Reduction
20.1
The Meaning of Oxidation and Reduction
Salt on icy roads can make driving safer, but the salt that clings to the metallic parts of cars can cause them to corrode or rust relatively quickly. This corrosion is one example of a chemical reaction called oxidation-reduction. You will learn about oxidation-reduction reactions.

3. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
What Are Oxidation and Reduction?
How is the gain or loss of oxygen in a chemical reaction linked to oxidation and reduction?

4. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
The substance gaining oxygen is oxidized, while the substance losing oxygen is reduced.
These reactions are called oxidation- reduction reactions and are also known as redox reactions.

5. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
Oxygen and Redox
A Bunsen burner oxidizes the methane in natural gas to carbon dioxide and water.
A Bunsen burner oxidizes the methane in natural gas to carbon dioxide and water.

6. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
Carbon is oxidized when charcoal burns.
When charcoal, which is mostly carbon, is burned in air, carbon dioxide and heat are produced.

7. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
Iron is oxidized when it rusts.
When items made of iron are exposed to moist air, the Fe atoms react with O2 molecules. The iron rusts; it is oxidized to compounds such as iron(III) oxide (Fe2O3).

8. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
Electron Shift in Redox Reactions
How is the gain or loss of electrons linked to oxidation and reduction?

9. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
Losing electrons is oxidation. Gaining electrons is reduction.
Oxidation is now defined to mean complete or partial loss of electrons or gain of oxygen.
Reduction is now defined to mean complete or partial gain of electrons or loss of oxygen.

10. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
Redox Reactions That Form Ions
When magnesium and sulfur are heated together, they undergo an oxidation-reduction reaction to form magnesium sulfide. Applying Concepts Where did the electrons lost by magnesium go?

11. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
When magnesium and sulfur are heated together, they undergo an oxidation-reduction reaction to form magnesium sulfide. Applying Concepts Where did the electrons lost by magnesium go?

12. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
The substance that loses electrons is called the reducing agent. The substance that accepts electrons is called the oxidizing agent.

16. for Conceptual Problem 20.1
Problem Solving 20.1 Solve Problem 1 with the help of an interactive guided tutorial.

17. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?
Redox With Covalent Compounds
This welder is using an oxyhydrogen torch to cut and weld steel. When hydrogen burns in oxygen, the redox reaction generates temperatures of about 2600°C.

18. What Are Oxidation and Reduction?
20.1
What Are Oxidation and Reduction?

19. 20.1
Corrosion
Corrosion
What happens to iron when it corrodes?

20. 20.1
Corrosion
Iron, a common construction metal often used in the form of the alloy steel, corrodes by being oxidized to ions of iron by oxygen.
Bridges like this one become unsafe because of corrosion.

21. Resistance to Corrosion
20.1
Corrosion
Resistance to Corrosion
Aluminum resists corrosion because it forms a protective coating of aluminum oxide.
Oxidation causes the complete corrosion of some metals. Aluminum resists such corrosion because it forms a protective coating of aluminum oxide. Applying Concepts How does the aluminum oxide on aluminum differ from the iron(III) oxide formed on corroding iron?

22. Controlling Corrosion
20.1
Corrosion
Controlling Corrosion
Painting a surface protects it from corrosion. Chromium metal also serves as a protective coating.
Painting a surface (left) protects it from the effects of the environment. Chromium metal also serves as a protective coating and imparts an attractive, mirrorlike finish (right). Like aluminum, chromium forms a corrosion-resistant oxide film on its surface.

23. 20.1
Corrosion
Zinc blocks attached to the steel hull of this ship oxidize instead of the iron, preventing corrosion.
Zinc blocks, the white rectangles in the photograph, are attached to the steel (iron) hull of this ship. The zinc blocks oxidize (corrode) instead of the iron, preventing the hull from corroding.

24. 20.1 Section Quiz.
20.1.

25. 20.1 Section Quiz.
1. Choose the correct words for the spaces. During oxidation, an element _______ electrons. During reduction, an element ________ electrons.
gains, loses
loses, gains
gains, donates
gains, accepts

26. 20.1 Section Quiz.
2. Choose the correct words for the spaces. During reduction, a substance may _______ oxygen or ________ hydrogen.
gain, lose
lose, gain
gain, gain
lose, lose

27. 20.1 Section Quiz..
3. The element that donates electrons in a redox reaction is called the reducing agent. This means the reducing agent is always
the more active element.
the less active element.
oxidized.
reduced.

28. 20.1 Section Quiz.
4. Which substance is the reducing agent in the following chemical reaction?
Fe2O3 + 3CO  2Fe + 3CO2
Fe2O3 CO Fe
CO2

29. the O2(g) in both reactions the O2(g) and H2O(l) in both reactions
20.1 Section Quiz.
5. The following equations describe the corrosion of iron to iron hydroxides in moist conditions.
2Fe(s) + O2(g) + 2H2O(l)  2Fe(OH)2(s)
4Fe(OH)2(s) + O2(g) + 2H2O(l) 4Fe(OH)3(s)
What substances in the equations are being oxidized?
Fe(s) and Fe(OH)2(s)
the O2(g) in both reactions
the O2(g) and H2O(l) in both reactions
Fe(OH)2(s) and Fe(OH)3(s)

30. END OF SHOW