New rocks become exposed Water evaporates from the surface of the sea Hydrogen in the air reacts with oxygen Acid rain falls onto limestone
Water becomes solid during chemical reactions Water becomes liquid during chemical reactions Trees drop their leaves Water falls from clouds as rain or snow
During combustion and respiration To control global warming To repair the ozone layer During photosynthesis
During combustion and respiration When dead things decay To repair the ozone layer During photosynthesis
Mud Nitrite Nitrate Nitrogen gas
Nitrogen fixing bacteria Nitrifying bacteria Denitrifying bacteria Neon bacteria