combustion
DESCRIPTION
Combustion. Students will identify and balance combustion reactions. What is a Hydrocarbon?. A hydrocarbon is chemical compound that only contains carbon and hydrogen. What is an Alkane ?. An alkane is a hydrocarbon that has the general formula of C X H 2X + 2 - PowerPoint PPT PresentationTRANSCRIPT
Combustion
Students will identify and balance combustion
reactions
A hydrocarbon is chemical compound that only contains carbon and hydrogen
What is a Hydrocarbon?
An alkane is a hydrocarbon that has the general formula of CXH2X + 2
C3H8 and C5H12 are examples of alkanes.
What is an Alkane?
Most alkanes are named after the number of carbon atoms.
The name
C5H12 = pentane
C8H18 = octane
Names of Alkanes
These numbers are the fuels octane rating.
The octane rating is the resistance of the fuel to autoignition
Octane Ratings
Octane Ratings are based on the combustion of these two molecules.
The products (if burned in open air) are water and carbon dioxide
Products in Combustion
When hydrocarbons burn in enclosed areas, they can also produce CO which is a deadly gas.
DANGER!
Air is mostly two types of gasses. N2 which has a mass of 28 grams/mole O2 which has a mass of 32 grams/mole
Methane (CH4) has a mass of 16grams/ mole
FYI: H2 = 2 grams/ mole is the lightest gas Propane C3H8 has a mass of 44grams/mole
is heavier than air which makes it more dangerous
Why do the bubbles float?
CH4 only has a small window of mixtures that burn. Methane only burns in mixtures between
4.4 – 15% methane to air
Acetylene burns 2.5 – 82%
See Wikipedia http://en.wikipedia.org/wiki/Flammability_limit
Why does the gas burn so slowly?
The candle supplies the energy to get the methane to start burning.
However, ones it starts, it supplies its own energy to react with the oxygen.
Energy Diagram
POTENTIAL ENERGY