Warm-UpWarm-UpNovember 24, 2014November 24, 2014

What do you know about combustion What do you know about combustion and/or oxidation-reduction reactions?and/or oxidation-reduction reactions?

ObjectiveObjective

SWBAT understand the chemistry of SWBAT understand the chemistry of combustion and the three types of combustion and the three types of heat transfer. heat transfer.

AgendaAgenda

1.1. CombustionCombustion

2.2. Oxidation-Reduction ReactionsOxidation-Reduction Reactions

3.3. Potential Energy DiagramsPotential Energy Diagrams

4.4. Heat TransferHeat Transfer

5.5. Combustion at a Sugar Plant ArticleCombustion at a Sugar Plant Article

6.6. Oklahoma City Bombing Oklahoma City Bombing Documentary Documentary

7.7. Exit SlipExit Slip

Combustion ReactionsCombustion Reactions

• Combustion reactions occur when a hydrocarbon reacts with oxygen gas.

• This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”:1) A Fuel (hydrocarbon)2) Oxygen to burn it with3) Something to ignite the reaction (spark)

Combustion ReactionsCombustion Reactions• In general:

CxHy + O2 CO2 + H2O• Products in combustion are

ALWAYS carbon dioxide and water. (although incomplete burning does cause some by-products like carbon monoxide)

• Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C8H18)

Combustion Combustion ReactionsReactions

Edgar Allen Poe’s drooping eyes and mouth are potential signs of CO poisoning.

CombustionCombustion

• Example• C5H12 + O2 CO2 + H2O

• Write the products and balance the following combustion reaction:• C10H22 + O2

5 68

Oxidation-Reduction ReactionsOxidation-Reduction Reactions

https://www.youtube.com/watch?https://www.youtube.com/watch?v=lQ6FBA1HM3sv=lQ6FBA1HM3s

Potential Energy DiagramsPotential Energy Diagrams

► Activation Energy is Activation Energy is the amount of the amount of energy to start a energy to start a reaction or the reaction or the energy needed so energy needed so that the reactants that the reactants bonds will break bonds will break and reform to make and reform to make productproduct

Exothermic ReactionsExothermic Reactions

► Release heatRelease heat► Reactants Ep is Reactants Ep is

higher than higher than Products Ep.Products Ep.

► Combustion Combustion reactions are reactions are exothermicexothermic

• Three methods of heat transfer…

• Three methods of heat transfer…

Three Heat Transfer MethodsConduction:

Conduction is the only means of transferring heat to the interior of fuels (wood, litter, duff).

High-density fuels (green wood) vs. low-density fuels (litter, decayed wood)

High density fuels have greater conductivity – more heat needed to raise temperature of surface layer

Transfer of heat from one molecule to another.

Example: touching your hand to a hot object

Radiation:

Transmission of heat by electromagnetic waves.

Examples of radiation: Heat from sun, fire place, stove

Contact between radiation source and affected body not necessary Example: preheating of fuels ahead of fire front

Absorption of radiation by woody fuels

– only by thin layer at surface (rest by conduction)

Convection:

Transfer of heat by movement of a gas or liquid (air).

Hot air moves vertically (exceptions: winds, slopes)

Examples: heating a pot of water, smoke from a fire.

What Factors can Increase

Heat Transfer?

Flames are brought

closer to the fuel

due to slope.

Factors that Increase Heat Transfer

Wind

The wind pushes the flames over...

...bringing the flames closer to the fuel.

Heat Transfer Video & SongHeat Transfer Video & Song http://video.search.yahoo.com/video/http://video.search.yahoo.com/video/

play;_ylt=A2KLqIL.JM5RpU8A5lD7w8QF;_ylu=X3play;_ylt=A2KLqIL.JM5RpU8A5lD7w8QF;_ylu=X3oDMTB2MWNmYzNpBHNlYwNzcgRzbGsDdmlkBoDMTB2MWNmYzNpBHNlYwNzcgRzbGsDdmlkBHZ0aWQDVjEzMQRncG9zAzc-?p=convectionHZ0aWQDVjEzMQRncG9zAzc-?p=convection%2C+conduction%2C+conduction%2C+radiation&vid=bc23b19f58302e316cced7%2C+radiation&vid=bc23b19f58302e316cced7db9ef2c3e3&l=2%3A44&turl=http%3A%2Fdb9ef2c3e3&l=2%3A44&turl=http%3A%2F%2Fts3.mm.bing.net%2Fth%3Fid%2Fts3.mm.bing.net%2Fth%3Fid%3DV.4529675467229482%26pid%3DV.4529675467229482%26pid%3D15.1&rurl=http%3A%2F%3D15.1&rurl=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%2Fwww.youtube.com%2Fwatch%3Fv%3DenrsfHG5eB8&tit=Conduction+convection%3DenrsfHG5eB8&tit=Conduction+convection+radiation+radiation%3A+Heat+transfer&c=6&sigr=11afno5c7&ag%3A+Heat+transfer&c=6&sigr=11afno5c7&age=0&fr=my-myy&tt=be=0&fr=my-myy&tt=b

Combustion at Sugar Plant Combustion at Sugar Plant ArticleArticle

Read and write a 3 full sentence Read and write a 3 full sentence summary.summary.

OKC Bombings DocumentaryOKC Bombings Documentary

1.1. What is the conspiracy of the Oklahoma What is the conspiracy of the Oklahoma City bombings? City bombings?

2.2. What does the former CIA director What does the former CIA director Woosley think the conspiracy involves? Woosley think the conspiracy involves?

3.3. What were the first leads that came out What were the first leads that came out and what did eyewitnesses report? and what did eyewitnesses report?

4.4. What information did they get from What information did they get from where the truck was rented? where the truck was rented?

5.5. How did they conclude that John Doe 1 How did they conclude that John Doe 1 was Timothy McVey? was Timothy McVey?

HomeworkHomework

Read Chapter 12, pgs. 434-443, Read Chapter 12, pgs. 434-443, Review #18-25Review #18-25

Exit SlipExit SlipNovember 24, 2014November 24, 2014

Go to m.socrative.com and enter Go to m.socrative.com and enter 417101417101

Question: Name one of the types of Question: Name one of the types of heat transfer and give a real world heat transfer and give a real world example. example.