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 (NaCl, Sugar..ect) and is a solid Compound- is when two or more elements are combined by chemical bonds (NaCl, Sugar..ect) and is a solid Solution- is when two or more elements are combined by chemical bonds and are in a liquid state. (every drop is the same concentration HCL, Vinegar) Solution- is when two or more elements are combined by chemical bonds and are in a liquid state. (every drop is the same concentration HCL, Vinegar)

3. Important Terms Mixture- is when two or more elements are combined but ARE NOT chemically bonded (liquid or solid) Mixture- is when two or more elements are combined but ARE NOT chemically bonded (liquid or solid) Heterogeneous mixture- Not an even mix throughout, (chocolate milk, salt and pepper, Italian salad dressing) Heterogeneous mixture- Not an even mix throughout, (chocolate milk, salt and pepper, Italian salad dressing) Homogeneous mixture- Even mix throughout (milk, sand, and smoke) Homogeneous mixture- Even mix throughout (milk, sand, and smoke)

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: STRONGEST CHEMICAL BOND Ionic-electrons are transferred from one element and give to another: 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 elements in both the reactants and products MAKE SURE ALL ARE LISTED ReactantsProducts ReactantsProducts AgAg AgAg NN NN OO OO NaNa NaNa ClCl ClCl

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. 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. 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

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 ReactantsProducts ReactantsProducts 1 C1C 1 C1C 4 H2 H 4 H2 H 2 O3 O 2 O3 O THIS CAN NOT HAPPEN! You must Balance the equation so that numbers of atoms for the reactants equal the same number for the Products 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. To do this we place numbers in front of the molecules in the formula to balance the atoms out To do this we place 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. 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. Homework 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