1. Basic Principles of Chemistry Unit 2: Chemical Reactions and Their Significance Lecture #9

2. Summary Matter... –Is composed of atoms which... are composed of protons, neutrons, and electrons AND make up molecules

3. Classes of Pure Substances

4. More About Matter Each pure substance is characterized by its own unique set of properties. –Physical –Chemical

5. Our Business The study of the physical and chemical properties of matter

6. Our Method The scientific method Making careful measurements and other observations Communicating our findings to others

7. The Dilemma Atoms are very tiny Atoms are very numerous

8. Tiny Atoms

9. Many Atoms

10. Counting by Weight

11. Counting Units Pair Dozen Gross Score Magnum Ream Turkey

12. Is This Really Necessary? Why do we need to be able to account for all the atoms and molecules in a sample? Can we account for all of the atoms or molecules in a sample?

13. A New Counting Unit The MOLE –One carbon (C) atom weighs 12.0 amu –One mole of carbon (C) atoms weighs 12.0 g

14. Avogadro’s Number The MOLE 6.02 x 10 23 items This is HUGE!

15. Avogadro’s Number One mole of marbles could cover Earth to a depth of 50 miles.

16. Avogadro’s Number One mole of pennies could give every man, woman, and child on Earth $1,000,000,000,000!

17. Avogadro’s Number A glass of water contains about 10 moles of water. This is more water molecules than grains of sand in the Sahara Desert.

18. Extra Credit Assignment “How Big is a Mole” Project