How many significant digits are in 2804

When the water vapor cools it condenses select a number that represents his process on the

If 90.0 grams of ethane reacted with excess chlorine,how many grams of dicarbon hexachloride would form

Need what is special about water as a compound? how does water regulate climate? what drives water evaporation?   why is the water vapor fresh water when it rises from the ocean? why might freshwater in the form of snow take longer to enter the water cycle again than liquid precipitation?   what is an aquifer? what role do people play in the water cycle? plz just answer as many as you can ! thx if you !