1. CHAPTER 2 Matter and Atoms 2.1 Matter and the Elements

2. 2 Key Questions Are there millions of unique kinds of matter or is the observed diversity due to combinations of a few ingredients? What types of changes occur in matter? Is matter “smooth” to the smallest scale?

3. 3 2.1 Matter and the Elements What are things made of? How many different kinds of substances can you identify?

4. 4 2.1 Matter and the Elements The “stuff” that we are made of is called matter. Chemistry tells us how one kind of matter can be changed into a completely different kind of matter. What are things made of?

5. 5 2.1 Matter and the Elements substance: a kind of matter that can’t be separated into other substances by physical means such as heating, cooling, filtering, drying, sorting, or dissolving. Corn oil is a pure substance

6. 6 2.1 Matter and the Elements mixture: matter that contains more than one substance. Corn oil is a pure substance Oil and vinegar dressing is a mixture of substances

7. 7 2.1 Matter and the Elements Is “pure orange juice” a pure substance? “Pure orange juice” Water Flavoring chemicals Citric acid Sugars Fruit pulp …

8. 8 2.1 Matter and the Elements Look at your desk – What is it made of? wood, metal… Can you think of a few physical properties? is it heavy? is it bendable? does it feel cold? can you scratch it? …

9. 9 2.1 Matter and the Elements Examples: Mass Density Color Physical properties can be measured or seen through direct observations. Physical properties

10. 10 2.1 Matter and the Elements Physical changes include changes in shape, phase or temperature.

11. 11 2.1 Matter and the Elements

12. 12 2.1 Matter and the Elements Chemical properties are observed when a substance changes into a different substance. IronRust Chemical change

13. 13 2.1 Matter and the Elements Signs that a chemical change has occurred

14. 14 2.1 Matter and the Elements Macroscopic and microscopic scales

15. 15 2.1 Matter and the Elements Each element is a unique type of atom. All oxygen atoms are identical. An oxygen atom is different from a silicon atom or a potassium atom. element: a substance that cannot be separated into simpler substances by chemical means.

16. 16 2.1 Matter and the Elements 1 grain of rice = 0.01 gram 1 hydrogen atom = 1.678 x 10 –24 grams = 0.000000000000000000000001678 grams How small is an atom?

17. 17 2.1 Matter and the Elements How would you organize all those elements?

18. 18 2.1 Matter and the Elements The periodic table

19. 19 2.1 Matter and the Elements

20. 20 2.1 Matter and the Elements The periodic table organizes elements according to how they combine with other elements (based on their chemical properties).

21. 21 2.1 Matter and the Elements

22. 22 2.1 Matter and the Elements Increasing atomic number

23. 23 2.1 Matter and the Elements Hydrogen Lightest element Atomic number: 1 Uranium Heaviest naturally occurring element Atomic number: 92 Increasing atomic number

24. 24 2.1 Matter and the Elements Elements that belong to the same group (column) have similar chemical properties.

25. 25 2.1 Matter and the Elements Reminder 1 atomic mass unit (amu) = 1.66 x 10 -24 g

26. 26 2.1 Matter and the Elements The atomic mass is the mass of: 1)a single atom in amu. 2)a mole of atoms in grams. One single hydrogen atom weighs 1.01 amu. One mole of hydrogen atoms weighs 1.01 g. What does that mean?

27. 27 2.1 Matter and the Elements The atomic mass is the mass of: 1)a single atom in amu. 2)a mole of atoms in grams. One single carbon atom weighs 12.0 amu. One mole of carbon atoms weighs 12.0 g. What does that mean?

28. 28 2.1 Matter and the Elements One mole contains 6.02 x 10 23 atoms Avogadro’s number

29. 29 2.1 Matter and the Elements How many moles are in 100 g of sulfur (S)?

30. 30 2.1 Matter and the Elements How many moles are in 100 g of sulfur (S)? Asked:The number of moles Given:The element is sulfur and there are 100 g Relationships:One mole of sulfur has a mass of 32.065 g

31. 31 2.1 Matter and the Elements How many moles are in 100 g of sulfur (S)? Asked:The number of moles Given:The element is sulfur and there are 100 g Relationships:One mole of sulfur has a mass of 32.065 g Solve: Answer:100 g of sulfur contains 3.12 moles of sulfur atoms.

32. 32 2.1 Matter and the Elements How many grams of calcium (Ca) do you need to have 2.50 moles of calcium? Asked:The number of grams Given:The element is calcium and there are 2.50 moles Relationships:One mole of calcium has a mass of 40.078 g

33. 33 2.1 Matter and the Elements How many grams of calcium (Ca) do you need to have 2.50 moles of calcium? Asked:The number of grams Given:The element is calcium and there are 2.50 moles Relationships:One mole of calcium has a mass of 40.078 g Solve: Answer:2.50 moles of calcium has a mass of 100. g.

34. 34 2.1 Matter and the Elements Physical properties can be seen and measured Chemical properties are observed when one substance is changed into another Elements are organized in a periodic table This allows to convert grams to moles and vice versa.