Across
- 3. Smallest part of an element that retains its properties
- 6. Organ that pumps blood
- 7. Process that uses oxygen to release energy from food
- 10. Gas taken in during photosynthesis
- 11. Organ that helps remove carbon dioxide from blood
- 12. Where digestion begins
- 14. Force that opposes motion
- 16. Substance made of two or more elements chemically joined
- 17. Tiny negatively charged particle in atoms
- 20. The main gas in the air we breathe
- 21. Energy type stored in stretched or compressed objects
Down
- 1. Name for stored chemical energy in food
- 2. Living part of the environment
- 4. Tube that carries air to the lungs
- 5. Metal that reacts vigorously with water
- 8. A mixture where substances are evenly spread
- 9. Organism that makes its own food
- 13. Unit of electrical resistance
- 15. Non-metal used in pencils
- 18. Muscle found only in the heart
- 19. Where bones meet