1. Student notes
CHEMICAL REACTIONS

2. CHEMICAL REACTIONS
Chemical reactions: Occur when chemical bonds break or new bonds form
*Atoms rearrange to form new substances*

3. CHEMICAL REACTIONS
A chemical reaction has occurred and a new substance has formed when:
A gas has formed
A precipitate (solid) has formed
Change in temp.
Change in color

4. CHEMICAL REACTIONS – CONTINUED
Chemical reactions summarize a reaction using formulas and symbols
Reactants are the substances at the beginning of the reaction; left of the arrow
Products are the substances at the end; right of the arrow
 “yields” or “forms”

5. CHEMICAL REACTIONS – CONTINUED
Examples:
Copper nitrate and zinc yield zinc nitrate and copper
Cu(NO3) Zn  Zn(NO3) Cu
Reactants = Cu(NO3) Zn
Products = Zn(NO3) Cu

6. LAW OF CONSERVATION OF MASS
Mass (or matter) cannot be created or destroyed during a chemical reaction

7. LAW OF CONSERVATION OF MASS
Mass of reactants = mass of products
All of the atoms present at the beginning of the reaction are present at the end of the reaction but they are rearranged

8. BALANCING EQUATIONS
Balanced Equations: Equation where the number of atoms and type of atoms are the same for reactants and products
*Coefficients: Number before the chemical formula*

9. BALANCING EQUATIONS
Element: # Compounds: #atoms/compound total # atoms
2H2O H=2x O=2x1
4Cu(NO3)2 Cu=4x1
N=4x1x O=4x3x2

10. Rules for balancing equations:
Count the number of atoms of each element on each side of the equation
Change or add COEFFECIENTS ONLY to get the number of atoms equal.

11. Rules for balancing equations:
Check work by counting atoms of each element on each side of the equation.
NEVER CHANGE SUBSCRIPTS!!!!!!!!!!!!

12. Types of Reactions:
Synthesis reactions: 2 or more substances combine to form another substance
2H2 + O2  2H2O
Decomposition reactions: one substance breaks down (or decomposes) into 2 or more simpler substance
H2CO3  H2O + CO2

13. Types of Reactions:
Single Replacement Reactions: one element replaces another in a compound; 1 element + 1 compound yields 1 element + 1 compound
Cu + 2AgNO3  Cu(NO3) Ag
Double Replacement Reactions:
AgNO3 + NaCl  AbCl + NaNO3

14. Examples: K + Cl2  KCl O2 + Cl2  Cl2O
HCl + Mg  MgCl2 + H K + F2  KF
HgCl2 + H2S  HgS + HCl

15. Chemical Reactions Law of Conservation of Energy:
Energy is never created or destroyed but can change form

16. Chemical Reactions
Exothermic reactions: Some form of energy is given off
More energy in the reactants than the products
Example: heat pack

17. Chemical Reactions
Endothermic reactions: Some form if energy is Some form if energy absorbed
Less energy in the reactants than the products
Heat is absorbed in the chemical bonds making the substance feel colder
Example: cold pack

18. CHARTS Acids Bases Releases H+1 ions when dissolved in water
Releases OH-1 ions when dissolved in water
Tastes sour
Tastes bitter
Not slippery
Slippery
Ph 0-6.9 Ph
Begin with H
End in OH

19. CHARTS Indicator Neutral Acid Base
Indicators: change in color when in contact with an acid or base
Indicator
Neutral
Acid
Base
Litmus paper
Blue stays blue
Red stays red
Blue turns red
Red turns blue
Phenolphthalein
Stays colorless
Pink
Purple cabbage water
Stays purple
Pink, red
Green (weak)
Yellow (strong)
Universal indicator
Stays green
Red
Purple
pH paper
Yellow= 7.0
Red/orange
Green/purple

20. pH SCALE pH Scale- Ranges from 0- 14 7.0 is neutral (not acid or base)
0 is strongest acid – lost of H+ ions
6.9 is weakest acid – few H+ ions
14 is strongest base – lots of OH- ions
7.1 is weakest base few OH- ions

21. Neutralization:
chemical reaction between an acid and base to form water and salt
HCl + NaOH  2H2O + NaCl
Acid base water salt

22. Neutralization:
Salt: formed when negative ions from an acid combine with positive ions form a base
Fe(OH) HNO3  Fe(NO3) H2O
Base acid salt water