Science 2022

2. organic matter used as a fuel
4. a brown deposit resembling soil
6. a force exerted by a machine or in a process
8. a metal made by combining two or more metallic elements
10. waste water and excrement conveyed in sewers
12. rising and falling of the sea
13. the smallest particle of a chemical element that can exist
14. a combustible black or dark brown rock consisting chiefly of carbonized plant matter
16. the natural home or environment of an animal, plant, or other organism
17. a simple machine
19. a small particle that can make you sick
21. a group of living organisms

1. the disposal of waste material by burying it
3. the curved path of a celestial object or spacecraft round a star, planet, or moon
5. a biological community of interacting organisms and their physical environment
7. The force with which an object near the Earth or another celestial body is attracted toward the center of the body by gravity
9. the level below which the ground is saturated with water
11. exhibiting or relating to magnetism
15. when rain turns acidic
18. the organic component of soil
20. a short, slender, sharp-pointed metal pin