p. 360, #14-20

14. CO2 and water vapor maintain the stable surface temperature of the Earth. When the sun rays hit the eEarth, gas molecules absorb most of the radiation, preventing the high levels of heat from reaching the Earth. During the nighttime, the heat that has been absorbed by the gasses is released, and this helps the temperature stay warm enough.

15.
a)
natural processes: the carbon cycle
human activities: CO2 released from cars
b)
natural processes: A cow's digestion which releases methane into the air

human activities: Burning of methane

16.
a) increase: a high amount of CO2 levels in the air, trapping the heat on Earth
b) decrease: An increase of gas molecules  because fewer rays would reach the surface

17. A greenhouse with transparent glass walls is much warmer than a structure with opaque wooden walls because the radiation waves that enter the greenhouse do not escape easily because they keep reflecting off of the glass back onto the ground.

18.
a)

b)

19. Methane, carbon dioxide, and limestone.

20. Carbon atoms go through the carbon cycle, which takes the carbon atoms through the atmosphere, biosphere, lithosphere, and hydrosphere. It enters the atmosphere when carbon is released as carbon dioxide. It enters the hydrosphere when it is used in plants for respiration and is in glucose form. It becomes part of the biosphere when the CO2 is exhaled from plants becoming oxygen,  that is inhaled by humans and exhaled as CO2 by humans. CO2 is also inhaled by underwater plants which also makes it part of the hydrosphere. It is also formed into limestone which makes it part of the lithosphere.