1. Chemical Bonds and Balancing Equations EQ: Why do chemicals react? What is the difference between compounds, mixtures, and solutions?

2. Important Terms Molecule- is two or more atoms combined and are physically attached. Molecule- is two or more atoms combined and are physically attached. Compound- is when two or more elements are combined by chemical bonds. Compound- is when two or more elements are combined by chemical bonds. Usually found as a solid. Usually found as a solid. Ex. H 2 O = Water Ex. H 2 O = Water Ex. NaCl = Sodium Chloride (Table Salt) Ex. NaCl = Sodium Chloride (Table Salt) Solution- is when two or more substances are combined by dissolving a substance in pure water. Solution- is when two or more substances are combined by dissolving a substance in pure water. Usually found as a liquid. Usually found as a liquid. Can be separated by boiling or distillation. Can be separated by boiling or distillation. Ex. Salt Water; Sugar Water Ex. Salt Water; Sugar Water

3. Important Terms Mixture- is when two or more substances are combined but ARE NOT chemically bonded. Mixture- is when two or more substances are combined but ARE NOT chemically bonded. Can be both solids and liquids. Can be both solids and liquids. Heterogeneous Mixture- Not an even mix throughout. Heterogeneous Mixture- Not an even mix throughout. Ex. Fruit Salad, Pepper, Lucky Charms Ex. Fruit Salad, Pepper, Lucky Charms Homogeneous Mixture - Even mix throughout. Homogeneous Mixture - Even mix throughout. Ex. Steel and Clear Salt Water Ex. Steel and Clear Salt Water

4. Recall Why do elements react? Why do elements react? To achieve a more stable electron configuration (full outer shell) To achieve a more stable electron configuration (full outer shell)

5. What types of bonds are created? Ionic electrons are transferred from one element and give to another. Ionic - electrons are transferred from one element and give to another. Metal joins with a Nonmetal STRONGEST CHEMICAL BOND Metal joins with a Nonmetal STRONGEST CHEMICAL BOND New terms New terms Cation-positive element Cation-positive element Anion-negative element Anion-negative element So sodium is a cation and chloride is the anion in NaCl(salt) So sodium is a cation and chloride is the anion in NaCl(salt)

6. Covalent Bond Atoms share electrons: NO ELECTRONS ARE SHIFTED OR REMOVED Atoms share electrons: NO ELECTRONS ARE SHIFTED OR REMOVED Can create either single or double bonds to achieve full outer shell Can create either single or double bonds to achieve full outer shell Most Commonly done with gases that do not have a full outer shell (O 2 Cl 2 N 2 ) Most Commonly done with gases that do not have a full outer shell (O 2 Cl 2 N 2 ) Atoms of the gases join up to achieve stability (weak bond, easily broken) Atoms of the gases join up to achieve stability (weak bond, easily broken)

7. Understanding Chemical Reactions Look at the following equation: Look at the following equation: The reactants are to the left of the arrow The reactants are to the left of the arrow The products are to the right of the arrow The products are to the right of the arrow ReactantsProducts ReactantsProducts Ag(NO 3 ) + NaCl -------  AgCl + Na(NO 3 ) Ag(NO 3 ) + NaCl -------  AgCl + Na(NO 3 )

8. Now list the number of atoms there are present for the Reactants and Products Reactants Reactants Ag Ag N O Na Na Cl Cl Products Products Ag N O Na Cl

9. Now write the number of atoms of each element REACTANTSPRODUCTS REACTANTSPRODUCTS 1 Ag 1 Ag 1 Ag 1 Ag 1 N 1 N 1 N 1 N 3 O 3 O 3 O 3 O 1 Na 1 Na 1 Na 1 Na 1 Cl 1 Cl 1 Cl 1 Cl

10. Counting Atoms Notice that ALL The atoms listed are EQUAL in number on BOTH SIDES of the reaction Notice that ALL The atoms listed are EQUAL in number on BOTH SIDES of the reaction In a chemical formula you assume the number 1 when no other number is listed In a chemical formula you assume the number 1 when no other number is listed

11. Counting Atoms Notice that oxygen has 3 as its number! This is because oxygen is part of a polyatomic molecule. There are 3 oxygen atoms joined with the formula Notice that oxygen has 3 as its number! This is because oxygen is part of a polyatomic molecule. There are 3 oxygen atoms joined with the formula Diatomic Molecule – “two” atoms combined to make a molecule. Diatomic Molecule – “two” atoms combined to make a molecule. Polyatomic Molecule – “three or more” atoms combined to make a molecule. Polyatomic Molecule – “three or more” atoms combined to make a molecule.

12. Now consider this formula CH 4 + O 2 ----------------> CO 2 + H 2 O CH 4 + O 2 ----------------> CO 2 + H 2 O ReactantsProducts ReactantsProducts CC CC HH HH OO OO

13. How many atoms are listed for the products and reactants Reactants C – 1 C – 1 H – 4 H – 4 O – 2 O – 2 Products C – 1 C – 1 H – 2 H – 2 O – 3 O – 3 THIS CAN NOT HAPPEN! You must Balance the equation so that numbers of atoms for the reactants equal the same number for the products.

14. Balancing Equations To do this we place coefficients (numbers) in front of the molecules in the formula to balance the atoms out To do this we place coefficients (numbers) in front of the molecules in the formula to balance the atoms out CH 4 + O 2 ----------------> CO 2 + H 2 O CH 4 + O 2 ----------------> CO 2 + H 2 O (Start with the atom with the highest number for either reactants or products) (Start with the atom with the highest number for either reactants or products) It would be H in the example It would be H in the example

15. Balancing Equations ReactantsProducts ReactantsProducts 1 C1C 1 C1C 4 H2 H 4 H2 H 2 O3 O 2 O3 O We need 2 more H in the products so we place a 2 in front of the water molecule We need 2 more H in the products so we place a 2 in front of the water molecule CH 4 + O 2 ----------------> CO 2 + 2 H 2 O CH 4 + O 2 ----------------> CO 2 + 2 H 2 O

16. Now Recheck ReactantsProducts ReactantsProducts 1 C1C 1 C1C 4 H4 H 4 H4 H 2 O4 O 2 O4 O Now we need to balance out the Oxygen in the Reactants. Now we need to balance out the Oxygen in the Reactants. CH 4 + 2 O 2 ----------------> CO 2 + 2 H 2 O CH 4 + 2 O 2 ----------------> CO 2 + 2 H 2 O

17. Recheck ReactantsProducts ReactantsProducts 1 C1C 1 C1C 4 H4 H 4 H4 H 4 O4 O 4 O4 O It is now balanced!!! It is now balanced!!!

18. Exit Slip Balance this equation (its harder than it looks) Balance this equation (its harder than it looks) Al + O 2 -----------> Al 2 O 3 Al + O 2 -----------> Al 2 O 3