Necessary because it keeps heat in and keeps the planet at the right temperature for life.
It can harm the planet if more pollution occurs and the greenhouse gas effect traps too much heat and causes global warming
14. compound
15. the concentration cannot be increased.
16. heterogenous mixtures
17. chocolate chip cookies
18. vegetable soup
19. a mixture is a pure substance a compound is not
20. Tastes sour
Answer:population can affect the level of oxygen in water because of the too much of oxygen being released
Explanation: