1. Combustion and Global Warming
Carbon dioxide (CO2) is recognized as contributor to the greenhouse effect
CO2 is produced from complete combustion
Complete combustion: Fuel (usually a substance containing C & H) + O2  CO2 + H2O

2. Combustion & Global Warming
Gasoline is composed primarily of octane (C8H18)
Ethanol (C2H5OH) is an alternative fuel
Write the balanced combustion reactions for each
First write down the reactants and products for each reaction without balancing, then balance.
Which produces more CO2 per molecule of fuel?

3. States of Matter
Attractive forces between molecules dictates the state of matter
Liquids have some attractive forces between molecules
Take shape of container have fixed volume

4. States of Matter Gases have least attractive forces between them
Recall: gases take the volume & shape of container
Solids: Lots of attractive forces between molecules
Have fixed shape and volume

5. Evaporation
Change in a state of matter from the liquid to the gas phase
Is reversible, reverse process called condensation
Requires energy
Evaporation of Water Visualization
Molecules escape from the liquid’s surface during evaporation

6. Vanilla Demonstration
What would happen to vanilla in a closed container?
Depends based upon:
Volume of container (gas)
Volume of liquid
Substance identity (vapor pressure)
Temperature (vapor pressure)
System would eventually reach equilibrium where rate of evaporation and condensation are equal

7. Some of the gas molecules will eventually strike the condensed phase and condense back into it.
When the rate of condensation of the gas becomes equal to the rate of evaporation of the liquid or solid, the amount of gas, liquid and/or solid no longer changes.
The gas in the container is in equilibrium with the liquid or solid.
The pressure exerted by the gas in equilibrium with a solid or liquid in a closed container at a given temperature is called the vapor pressure.

8. Vapor Pressure
Higher Temperature
Lower Temperature
At higher temperature, more molecules have enough energy to escape from the liquid or solid. At a lower temperature, fewer molecules have sufficient energy to escape from the liquid or solid.
High vapor pressure at high temp, low vapor pressure at low temp.

9. Vapor Pressure
When the vapor pressure equals the pressure of the atmosphere, substance boils
Note: substances do have vapor pressure at temperatures below boiling
Example: glass of water left out for days