1. Chapter 4: Changes in matter

2. What is happening to matter in these pictures?

3. What is happening to matter in these pictures?

4. Physical Changes No change in the properties of the matter Atoms and molecules of the substance do not change Often changes in state or form

5. What is happening to matter in these pictures?

6. Chemical Changes Change the properties of the matter Bonds between atoms are rearranged, and new molecules are formed

7. What is happening to matter in these pictures?

8. Nuclear Transformation Changes happen in the nucleus of the atom New elements are formed

9. Chemical changes

10. How do we know that a chemical change has occurred? Release of a gas

11. Emission or absorption of heat Emission or absorption of light How do we know that a chemical change has occurred?

12. Change in color Formation of a precipitate

13. We write out chemical changes or CHEMICAL REACTIONS in equations CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O (g) “Methane reacts with oxygen to form carbon dioxide and water vapor.” “1 molecule of methane reacts with every 2 molecules of oxygen to form 1 molecule of carbon dioxide and 2 molecules of water vapor.” Before the chemical reaction Reactants: CH 4 + 2 O 2 After the chemical reaction Products: CO 2 + 2 H 2 O Number of atoms

14. Rules for balancing chemical equations 1.Coefficients must be whole numbers (no fractions) 2.Coefficients have to be as small as possible 3.New substances must never be added and existing substances must never be removed 4.It is easier to save oxygen and hydrogen until last 5.Check the final equation

15. Example #1 H 2 (g) + O 2 (g) H 2 O (l) Before the chemical reaction Reactants: H 2 + O 2 After the chemical reaction Products: H 2 O Number of atoms

16. Practice #1 K 2 O + H 2 O KOH Before the chemical reaction Reactants: K 2 O + H 2 O After the chemical reaction Products: KOH Number of atoms

17. Practice #2 Na + H 2 O NaOH + H 2 Before the chemical reaction Reactants: Na + H 2 O After the chemical reaction Products: NaOH + H 2 Number of atoms

18. Practice #3 The following reaction is the unbalanced equation for a chemical reaction involving iron (Fe) and water (H 2 O): Fe + H 2 OFe 2 O 3 + H 2 In its reduced form, what is the coefficient of hydrogen gas (H 2 ) in the balanced equation for this reaction?

19. Practice #4 CO 2 + H 2 O C 6 H 12 O 6 + O 2 Before the chemical reaction Reactants: CO 2 + H 2 O After the chemical reaction Products: C 6 H 12 O 6 + O 2 Number of atoms