Sorry this might not be great but when the air is cold the molecules are dense which means they are much closer together and hit each other but when they air is hot the molecules aren’t as dense which means they are more spread out. so as the cold air molecules are closer together, more of them could fit inside the balloon but with hot air since the molecules are so far apart not as many can fit in as they take up more as they spread and hit the side of the balloon
Not sure if this is what your looking for, but hope it helps. Nitrogen gas can be changed into nitrogen compound through nitrogen fixation, which is the conversion of nitrogen gas to ammonia, that are absorbed by the plant to make protein. Another way is through animals eating plants and obtaining nitrogen, which is later released, by decomposes, when the organism dies.
C. combustion I think. hope this helps
The acceleration of gravity in low Earth orbit is a fraction smaller than it is on the Earth's surface, like maybe 15% less.
The astronauts feel no gravity at all, because they and everything around them are constantly falling.