Across
- 4. Breathing is part of what nervous system.
- 5. Tells us the number electrons in an atom.
- 7. A form of radiation.
- 11. The variable that is changed.
- 14. A testable explanation or guess.
- 15. Part of the endocrine system.
- 16. Part of the nervous system.
- 17. Piece of evidence for continental drift.
- 18. Shared in an ionic bond.
- 20. Used to improve reliability.
Down
- 1. Different forms of a characteristic.
- 2. Least penetrating form of radiation.
- 3. Same element with different neutron number.
- 6. When half an isotope disappears.
- 8. Convection currents occur here.
- 9. We live on this layer of the Earth.
- 10. We keep this the same in an experiment.
- 12. Used during respiration.
- 13. The variable that is measured.
- 19. Shape of DNA.