Across
- 2. The rusted, orange version of gold
- 4. ______ chloride
- 5. The protein in your teeth
- 7. A silvery gray metal that has a planet named after it
- 8. The substance you always need from your food
- 10. A lustrous metal found in Earth's crust
- 12. Fills up birthday balloons
- 15. Trees take this gas in to help us breathe
- 17. What they add to salt
- 19. Makes up the substance that entinguishes fire
- 20. One step below gold
Down
- 1. What comes before "foil" on your box of foil
- 3. You need it to breathe
- 6. Pencil substance was once toxic
- 9. The softest lanthanide
- 11. The substance in pools that stings your eyes
- 13. Tuna are dying from the ______ in their blood
- 14. What the bars in the Treasury are made of
- 16. Atomic number 7
- 18. The best material to use for a safe