Across
- 4. substances created by plants and animals that are poisonous
- 5. First or Earliest known
- 6. any substance that has a defined composition
- 7. a procedure intended to establish the quality, performance, or reliability of something
- 8. Introduction of contaminants
- 10. able to cause harm
Down
- 1. HG Atomic number 80
- 2. a scientific procedure undertaken to make a discovery
- 3. a circumstance that complicates something; a difficulty
- 9. causing harm