1. Chemical & Physical Changes

2. Definitions
Physical Property: a property that can be seen or measured without changing the identity of the substance
Examples: color, size, density, melting point
Chemical Property: the ability or inability of a substance to react with or change into other substances
Examples: flammability, reactivity

3. 5 Signs of a Chemical Change
Release of light
Drastic color change
Formation of precipitate
Precipitate: solid produced during a chemical reaction in a solution
Gas/odor released
Temperature change

4. Reactions & Equations

5. How do I represent a chemical rxn?
Reactant Reactant 2 → Product Product 2
Reactants are starting substances.
Products are substances formed.
Arrow shows direction of progress.
A “+” sign is placed between reactants and products to separate them.
Symbols are used to show physical state of reactants and products –
(s) solid, (l) liquid, (g) gas, (aq) dissolved in water.

6. Balancing Chemical Equations
We use coefficients in front of reactants and products – always whole numbers – and tells you the smallest number of particles involved in the reaction.
Steps:
Write skeleton equation.
Count the # of elements in reaction.
Change the coefficients to make the # of atoms of each element equal on both sides of the equation.
Write the coefficients in their lowest possible ratio.
Check your work.

7. Conservation of Mass
Matter is neither created nor destroyed in a chemical reaction.
Number of atoms in reactant equals number of atoms in product.
Sum of mass in reactant equals sum of mass in product.
Ex. 2H2O2 → 2H2O + O2
68.0g g + _?_
68.0g – 32.0g = 36.0 g

8. Redox Reactions
Redox reactions are the transfer of electrons from one reactant to another...
When there is oxidation, there is also reduction. The substance which loses electrons is oxidized. The substance which gains electrons is reduced.
Rules:
The oxidation number is determined by
an element in the uncombined state or diatomic elements are Zero (neutral).
a monatomic ion & polyatomic ion equals the charge on the ion
Oxidized = positive charge (lose electrons)
Reduced = negative charge (gained electrons)
LEO THE LION GOES GER
Lose electrons oxidized, Gained electrons reduced

9. Let’s Practice: 2Na + FeCl2 → 2NaCl + Fe 2C2H2 + 5O2 → 4CO2 + 2H2O
2PbS + 3O2 → 2SO2 + 2PbO

10. More Practice….. 2H2 + O2 → 2H2O Cu + HNO3 → CuNO3 + H2
AgNO3 + Cu → CuNO3 + Ag

11. Single Replacement Reactions and Reactivity

12. Activity Series
A chart of metals listed in order of declining relative reactivity. The top metals are more reactive than the metals on the bottom.

13. Single replacement
One element replaces a second element in a compound.
the more reactive metal will replace the least reactive metal.
the more reactive nonmetal will replace the least reactive nonmetal.
General equation: A + BX → AX + B
EX. 2AgNO3 (aq) + Cu(s) → 2Ag(s) + Cu(NO3)2(aq)
Silver nitrate reacts with copper to produce silver and copper

14. Let’s Practice… Cu + 2AgNO3 → 2Ag + Cu(NO3)2
Fe + Cu(NO3)2 → Fe(NO3)2 + Cu
Ca + 2H2O → Ca(OH)2 + H2

15. More Practice… Zn + 2HCl → ZnCl2 + H2 Cl2 + 2NaBr → 2NaCl + Br2
Br2 + 2KI → 2KBr + I2