Samples of the air we breathe that were taken from different parts of the world have a been found to contain about 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and 0.07% other gases. Based on this analysis, which is the correct classification for air? Homogenous mixture
Heterogenous mixture
Compound
Element

What provides structure to the human body?

Asample of aluminum foil contains 8.60 × 1023 atoms. what is the mass of the foil?

Select the correct text in the passage. which sentences describe examples of sustainable living? i live in an old apartment building downtown, but my company is based in an office park on the outskirts of the city. i drive an old car that needs to be replaced. i plan to buy a hybrid for better gas mileage, but for now i am able to carpool with a couple of friends from work. the drive to the office park is about 45 minutes each way, but we do get to work in a modern building. the architects just received a leed certification for the design.