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

2. 2 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?

3. 3 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

4. 4 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

5. 5 2.1 Matter and the Elements Is “pure orange juice” a pure substance? “Pure orange juice” Water Flavoring chemicals Citric acid Sugars Fruit pulp …

6. 6 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? …

7. 7 2.1 Matter and the Elements Examples: Mass Density Color Physical properties can be measured or seen through direct observations. Physical properties

8. 8 2.1 Matter and the Elements Physical changes include changes in shape, phase or temperature.

9. 9 2.1 Matter and the Elements

10. 10 2.1 Matter and the Elements Chemical properties are observed when a substance changes into a different substance. IronRust Chemical change

11. 11 2.1 Matter and the Elements Signs that a chemical change has occurred

12. 12 2.1 Matter and the Elements Macroscopic and microscopic scales

13. 13 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.

14. 14 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?

15. 15 2.1 Matter and the Elements How would you organize all those elements?

16. 16 2.1 Matter and the Elements The periodic table

17. 17 2.1 Matter and the Elements

18. 18 2.1 Matter and the Elements The periodic table organizes elements according to how they combine with other elements (based on their chemical properties).

19. 19 2.1 Matter and the Elements

20. 20 2.1 Matter and the Elements Increasing atomic number

21. 21 2.1 Matter and the Elements Hydrogen Lightest element Atomic number: 1 Uranium Heaviest naturally occurring element Atomic number: 92 Increasing atomic number

22. 22 2.1 Matter and the Elements Elements that belong to the same group (column) have similar chemical properties.

23. 23 2.1 Matter and the Elements Reminder 1 atomic mass unit (amu) = 1.66 x 10 -24 g

24. 24 2.1 Matter and the Elements The atomic mass is the mass of: 1)a single atom in amu. One single hydrogen atom weighs 1.01 amu. What does that mean?

25. 25 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.