Merry Christmas Don,
The two most abundant elements in the troposphere are Oxygen and Nitrogen. Oxygen has an 16 atomic unit mass while Nitrogen has a 14 atomic units mass. Since both these elements are diatomic in the troposphere (O2 and N2), the atomic mass of diatomic Oxygen is 32 and the diatomic mass of Nitrogen is 28.
Water vapor (H2O) is composed of one Oxygen atom and two Hydrogen atoms. Hydrogen is the lightest element at 1 atomic unit while Oxygen is 16 atomic units. Thus the water vapor atom has an atomic mass of 1 + 1 + 16 = 18 atomic units. At 18 atomic units, water vapor is lighter than diatomic Oxygen (32 units) and diatomic Nitrogen (28 units). Thus at a constant temperature, the more water vapor that displaces the other gases, the less dense that air will become.
You may be familiar with the concept that moist air is less dense than dry air. This is true when both have the same temperature or when the moist air is warmer. Said in another way, air with a greater percentage of water vapor will be less dense than air with a lesser percentage of water vapor at the same temperature. Often people erroneously believe that moist air is denser than dry air because very moist air is more difficult to breathe than dry air.
I copied that from: http://www.theweatherprediction.com/habyhints/260/
Now I have another problem that I need some help with: Burning one gallon of gasoline which weighs about 6.3 pounds, creates 19.64 pounds of carbon dioxide. A medium growth coniferous (evergreen) tree, planted in an urban setting and allowed to grow for 10 years, sequesters 23.2 lbs of carbon. This estimate assumes the trees are planted when they are approximately 4.5 feet tall (the typical size of tree purchased in a 15-gallon container). Once again, we need to convert this estimate to pounds of CO2 removed from the atmosphere.
(23.2 lbs C) x (44 units CO2 / 12 units C) = 85.1 pounds of CO2
A medium growth evergreen tree, planted in an urban setting and allowed to grow for 10 years, absorbs approximately 85 pounds of carbon dioxide.
Then according to a table at the bottom of this page, http://www.science20.com/science_motherhood/i_wanna_go_green%E2%80%A6_so_show_me_math-2490
running 4 bags of charcoal through a charcoal grill would produce 44 pounds of CO2.
So does that mean that putting 8 bags of charcoal into your Geo charcoal gasifier would produce about at much CO2 as burning 1 gallon of gasoline?
If all the heat generated when making charcoal was used for heating our house, and the CO2 was ignored....then??? Still thinking on this one..