Across
- 3. repeating with small improvements
- 7. certain heavy metals that react easily with other elements
- 8. the process of returning the land to its former environmental condition
- 10. the reduction of one desirable characteristic in order to increase another
- 14. the conversion of kinetic energy in water to electric energy
- 15. combustable material stored in fossilized organisms
- 17. the way engineers identify and solve problems
- 18. a natural material made up of one or more minerals
- 19. use of a resource in amounts that do not exceed its production
Down
- 1. a limit or restriction on the solution
- 2. a sedimentary rock that contains kerogen, a solid bituminous material
- 4. a limited amount of the resource exists
- 5. contain bitumen, a thick, sticky substance that does not flow like petroleum
- 6. the recovery of useful material from waste
- 9. the resource can be replaced at the rate it is made
- 11. the required or desired properties of a solution
- 12. the conversion of heat energy from the Earth's interior to electric energy
- 13. mixtures of metals
- 16. the process by which materials are pumped underground to break up rock and release oil or natural gas