Corrosion and Combustion

1. Corrosion and Combustion SNC1P Mr. M. Couturier

2. Precious Medals • Question: You discover that one of your deceased relatives earned medals during both the Second World War and the Korean War and you are very proud of your relative’s contribution to his country. They have been given to you by inheritance. They are in perfect condition. How would you be able to display them while not damaging them to the elements (to the environment)?

3. Corrosion • Corrosion is the chemical reaction between metals and oxygen. One of the most common corrosion reactions is known as rusting: the reaction between iron and oxygen. 2Fe + O2 2FeO • Corrosion can also occur if iron is placed in water, because water contains oxygen. Fe + H2O  FeO + H2

4. Corrosion • Not all metals react poorly to corrosion. Unlike iron which will eventually corrode completely, Aluminum will only corrode on its surface. The aluminum oxide then forms a protective layer which prevents further corroding. • THINK about the burning of a book. Books tend to burn on the outside and can protect the inside of the book.

5. Corrosion • When silver (look at silverware) cutlery, coins or jewelry is exposed to oxygen it tarnishes. • All these terms (rusting, tarnishing, oxidizing, corroding) mean the same thing but are used for various elements in layman's terms.

6. Preventing Corrosion • Depending on the purpose of the object being created, various metallic elements which react differently to oxygen may be used. One reason that gold is so valuable is the fact that its reaction to oxygen is so slow. Hence gold from ancient civilizations are still recognizable and can still be used (gold coins, jewelry, etc).

7. Preventing Corrosion • Also, various alloys can be created such that once the outside of the object corrodes (like nickel, copper, aluminum, etc.). It is also possible not to use metals, but rather synthetic fibers such as plastic or fiberglass.

8. Preventing Corrosion • Why does the Statue of Liberty in New York, USA or the Eiffel Tower in Paris, France, not corrode? • THINK and discuss.

9. Preventing Corrosion • Both the Statue of Liberty and the Eiffel Tower are covered by several layers of paint. Paint, which comes in many forms (latex, acrylic, oil, alkyd, etc.) coat the metal against oxygen or water. If the metal never comes in contact with any form of oxygen, it will NOT react by corroding.

10. Precious Medals • Question: You discover that one of your deceased relatives earned medals during both the Second World War and the Korean War and you are very proud of your relative’s contribution to his country. They have been given to you by inheritance. They are in perfect condition. How would you be able to display them while not damaging them to the elements (to the environment)?

11. Precious Medals • THINK about how comic book collectors protect their X-MEN comic books. In see-through plastic folders. • THINK about how hockey card enthusiasts protect their Montreal Canadiens rookie cards? In see-through plastic card holders … and these are not even metal. • THINK about how coin collectors protect their precious coins from the elements? In plastic coin pockets.

12. Precious Medals • If your answer was to display them in an air-tight display case, then you’ve kept your medals from reacting with oxygen. This will prevent them from corroding over the years and you will be able to show off this family treasure with pride.

13. Combustion • A combustion reaction usually involves a hydrocarbon (fossil fuel) and oxygen. The result of a combustion reaction is the release of energy in the form of heat and light as well as carbon dioxide and water. The standard equation for a combustion reaction is: CxHy + O2 CO2 + H2O + energy

14. Fossil Fuels • Since fossil fuels are made up of molecules of hydrogen and carbon, they are rightfully called hydrocarbons. As you saw from the previous equation, the hydrocarbon is represented by CxHy, where x is the number of carbon atoms and y is the number of hydrogen atoms.

15. Hydrocarbons

16. Methane Combustion • Example: the equation for the combustion of methane is as follows: CxHy + O2 CO2 + H2O + energy CH4 + O2 CO2 + H2O + energy CH4 + 2O2 CO2 + 2H2O + energy

17. Word Equations • In the previous example, the reactants are listed on the left. The reactants are the chemicals that about being mixed. The products are then written on the right. The products are the chemicals that have been created by the reaction (and should include energy as some was released).

18. Propane Combustion • Example: notice that in this equation, the reactants are propane and oxygen while the products are carbon dioxide, water and energy. CxHy + O2 CO2 + H2O + energy C3H8 + O2 CO2 + H2O + energy C3H8 + 5O2 3CO2 + 4H2O + energy

19. Global Problem • Did you know that the Greenhouse Gas Effect derives from our society’s inability to function without burning fossil fuels. Since we burn fossil fuels or hydrocarbons, we release mind-boggling quantities of carbon dioxide into the atmosphere. Carbon dioxide traps the Sun’s radiation which warms the inner atmosphere (hence the Greenhouse Gas Effect). There is a solution!

20. Imagine This! • What if your car ran on hydrogen? The equation would look like this. 2H2 + O2 2H2O + energy • Did you notice that the exhaust was WATER? Then you would plug your car into your house at night which would do this … 2H2O + energy  2H2 + O2