<span> the atmosphere holds about 21 per cent oxygen. Over the Earth’s 4.6 billion year history, oxygen did not appear in the atmosphere until perhaps about 2.5 billion years ago. Since then, oxygen levels have fluctuated in tandem with global geological and biological events, such as mass extinctions.</span>
Explanation:
water evaporates because when h2o (water) particles heat up, they gain energy causing them to start to vibrate. this moves the oarticles further and further away from eachother and making the substance less dense, and turning it into a gas. meaning it has evaporated
Answer: The mass of
and
produced are 336.6 g and 183.6 g respectively.
Explanation:
The combustion reaction between propane and oxygen leads to formation of carbon dioxide and water.
Law of Conservation of mass states that the mass will remain constant for a balanced equation. This is carried out when the total number of atoms on reactant side is same as the total number of atoms on the product side. Thus the equation must be balanced.

a) 1 mol of propane produces = 3 moles of
Thus 2.55 mol of propane produces =
mass of 
b) 1 mol of propane produces = 4 moles of
Thus 2.55 mol of propane produces =
mass of
The mass of
and
produced are 336.6 g and 183.6 g respectively.