1. Chapter 8 Chemical Reactions

2. A chemical reaction is a process in which the physical and chemical properties of the original substances change as new substances with different physical and chemical properties are formed

3. Law of Conservation of Mass
During a chemical or physical change, all mass remains the same.
Mass is neither created nor destroyed.

4. Parts of a chemical reaction
Subscript tells the # of atoms in molecule
Coefficient tells # of molecules in reaction
2 H2 + O H2O
coefficient
coefficient
subscript

5. Parts of a chemical equation
Reactant is what goes into a chemical reaction
Product is what results in the reaction
2 H2 + O H2O
product
reactant
reactant

6. The ease with which atoms will form bonds is its bonding capacity.
Capacity to react
The ease with which atoms will form bonds is its bonding capacity.
This capacity is directly related to the electrons and their placement and number within the energy levels.

7. What happens when a chemical reaction occurs?
Atoms can form molecules
Molecules can break apart to form atoms
Molecules can react with other molecules

8. Balancing Equations Start with the first atom on the reactants side
Count the total number of atoms of the element on left and then on the right
Add a coefficient in front of atom(s) or compounds where necessary
Never change a subscript
Go back through each atom and recheck and/or change until # are equal on both sides of the equation

9. Types of Chemical Reactions
SYNTHESIS
2 or more substances combine
DECOMPOSITION
complex substance breaks down
SINGLE - REPLACEMENT
uncombined element replaces another element in a compound
DOUBLE - REPLACEMENT
atoms of 2 compounds replace each other (a flip-flop)

10. synthesis
Simple molecules or compounds combine to make a new and more complex substance
2 H2 + O H2O

11. decomposition
A complex substance breaks down into simpler substances
2 H2O H2 + O2

12. single-replacement 2Na + 2H2O 2NaOH + H2
Single element replaces another element within a compound
2Na + 2H2O NaOH + H2

13. double-replacement
Different atoms in two different compounds replace each other
MgCO3 + 2HCl MgCl2 + H2CO3

14. In any chemical reaction: some energy is needed to start the change some energy is involved during the reaction

15. ACTIVATION ENERGY is what is needed to get a reaction started
Ex: striking a match

16. Energy involved in the reaction can be either:
Exothermic or Endothermic

17. Exothermic ex means out therm means heat
energy is released during reaction
the energy in the reactants are higher than the products
Ex: fireworks

18. Endothermic endo means in therm means heat
energy is absorbed during reaction
the energy in the products are higher than the reactants
Ex: chemical ice

19. Kinetics is the study of reaction rates
In order to react, atoms must collide.
In order for bonds to be broken, formed or reformed, particles must collide at precisely the correct angle with the proper amount of energy.

20. Four factors that influence the collision theory are . . .
Rates of Chemical Reactions
The more collisions, the faster the rate of the chemical reaction
Four factors that influence the collision theory are . . .

21. concentration surface area temperature catalysts
the amount of reactants present
surface area
amount of exposed material
temperature
higher temperature causes atoms to display more energy & reaction rate is increased
catalysts
increases speed by decreasing the activation energy needed, but does not enter the reaction
called enzymes in living organisms