Part 1: Getting to know the Legos and Combustion (burning fuel in cars)1. Yes, this is a perfect reaction. A perfect reaction means that the reactants and products have the same amount of molecules. On the left side, there are 3 Cs, 8 Hs and 10 Os while on the right side there are 3 Cs, 8 Hs and 10 Os also thereby making it a perfect reaction since nothing is missing nor were any extra molecules created. Carbon and carbon dioxide are potential leftover atoms/molecules from incomplete combustion. If this is the case, there will be climate change where more carbon for example could potentially keep more heat in the atmosphere.Part 2: Incomplete CombustionIf there were less oxygen molecules as below,C3H8 + 4O2 X + Ysome possible products would be water, carbon dioxide and carbon monoxide. Some sample reactions would be the following:C3H8 + 4O2 4H2O + C + 2CO2 C3H8 + 4O2 4H2O + CO2 + 2COPart 3: Air Pollution1. I think the cause(s) of incomplete combustions are lack of O2 in the atmosphere, something that went wrong in mixing of O2 and fuel such as propane, or not enough time for the reaction to happen. Due to a lack of O2 in the atmosphere, CO2 cannot be formed and hence pollutants such as C and CO will be produced. There will be times where O2 and fuel do not mix properly due to several reasons such as other atoms in the atmosphere be mixed into the combustion. On the other hand, not all reactions take the same amount of time so of course some reactions will be incomplete due to lack of time. 2. O2 is the limiting factor because it is present in most pollution reactions and will be consumed entirely.