Across
- 2. the process by which complex organic substances are broken down into simple organic matter.
- 3. the ability of a mineral to resist scratching
- 9. a chart that arranges all the known elements according to their atomic number
- 10. substance made up of one type of atom
- 11. the temperature at which a solid melts to liquid
- 13. positively charged particle
- 14. proteins that act as a biological catalyst
- 15. the smallest unit in an element
Down
- 1. minimum energy required to start a reaction
- 4. an alloy of carbon and iron
- 5. vertical column in the periodic table
- 6. a group of atoms bonded together
- 7. the amount of mass per unit volume
- 8. the second most abundant mineral in the earth's crust
- 12. atoms of the same element that contain different numbers of neutrons