Chemical Bonds and Balancing Equations

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 • 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)

3. Important Terms • 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) • Homogeneous mixture- Even mix throughout (milk, sand, and smoke)

4. Recall • Why do elements react? • 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 • New terms • Cation-positive element • Anion-negative element • 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 • 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 (O2 Cl2 N2 ) • Atoms of the gases join up to achieve stability (weak bond, easily broken)

7. Understanding Chemical reactions • Look at the following equation: • The reactants are to the left of the arrow • The products are to the right of the arrow • Reactants Products • Ag(NO3) + NaCl ------- AgCl + Na(NO3)

8. Now list elements in both the reactants and productsMAKE SURE ALL ARE LISTED • Reactants Products • Ag Ag • N N • O O • Na Na • Cl Cl

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

10. 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

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

12. Now consider this formula • CH4 + O2 ----------------> CO2 + H2O • Reactants Products • C C • H H • O O

13. How many atoms are listed for the products and reactants • Reactants Products • 1 C 1C • 4 H 2 H • 2 O 3 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

14. To do this we place numbers in front of the molecules in the formula to balance the atoms out • CH4 + O2 ----------------> CO2 + H2O • (Start with the atom with the highest number for either reactants or products) • It would be H in the example

15. Reactants Products • 1 C 1C • 4 H 2 H • 2 O 3 O • We need 2 more H in the products so we place a 2 in front of the water molecule • CH4 + O2 ----------------> CO2 + 2 H2O

16. Now Recheck • Reactants Products • 1 C 1C • 4 H 4 H • 2 O 4 O • Now we need to balance out the Oxygen in the Reactants. • CH4 + 2 O2 ----------------> CO2 + 2 H2O

17. Recheck • Reactants Products • 1 C 1C • 4 H 4 H • 4 O 4 O • It is now balanced!!!

18. Homework • Balance this equation (its harder than it looks) • Al + O2 -----------> Al2O3