1. PROPERTIES AND CHANGES

2. Matter can be described in terms of:
Physical Properties – characteristics that are observed without changing the matter into another substance
Chemical Properties -- characteristics that describe the ability of matter to change into a new substance

3. Changes of Matter
Physical change: alters form or appearance, does not make a new substance
Chemical change: new substance is formed

4. Chemical change occurs when chemical bonds break and/or new bonds form.
When Oxygen gas (O2) comes in contact with Magnesium, the bond between the two Oxygen atoms is broken.
Each Oxygen atom will then take two electrons from Magnesium.
Since Magnesium lost electrons, it now has a positive (+) charge, Oxygen gained electrons and has a negative (-) charge.
Opposite charges attract and Magnesium Oxide (MgO) is formed

5. Chemical reactions involve two kinds of change
– 1. CHANGE IN MATTER (new substance)
NEW MATTER = NEW PROPERTIES
Property Changes to look for:
Color change
Formation of a PRECIPITATE – solid that forms when two solutions are mixed (state change)
Gas formation (bubbles – state change)
Temperature change
Light production
Change in odor/taste

6. 2. CHANGE IN ENERGY – exo- or endo-

7. Exothermic Reaction – energy releasing,
High to Low

8. Endothermic reaction – energy absorbing
Low to High

9. Rates of Chemical Reaction
Speeding up or slowing down reactions

10. Surface Area – Area of a substance that is exposed
The more of a substance that is exposed, the faster a reaction can occur
Temperature
Increasing Temperature speeds up reactions because:
Faster moving particle come in contact more often
Concentration – amount of substance in a given volume
Increasing concentration speeds up chemical reactions by providing more particle to react

11. b
Using catalysts (speed up chemcial reactions) and inhibitors (decrease rate of reaction)
Enzymes – natural biological catalyst
Preservatives – inhibitors added to food

12. LAW OF CONSERVATION OF MASS
During a chemical reaction, matter is not created or destroyed, it is changed from one form to another

13. Some reactions seem to violate this principle because they are in an:
Some reactions seem to violate this principle because they are in an: OPEN SYSTEM – system in which matter can enter from or escape to the surroundings.
Example – a fire burning
CLOSED SYSTEM -- system in which matter can not escape
Example – a chemical reaction in a plastic bag

14. Describing Chemical Reactions
CHEMICAL EQUATION –shows a chemical reaction using chemical formulas (CO, NaCl) and symbols, not words
Structure:
Reactants – what you start with, left side
Products – new substance that was produced, right side
 is read as “yields”

15. BALANCING CHEMICAL EQUATIONS
Equations must have the same number and type of atoms on each side (Law of Conservation of Mass)
Subscript – number below an element symbol, tells number of atoms of that element in the molecule
Coefficients – number placed in front of a chemical formula (2CO, 4NaCl), tells the number of molecules of a substance

17. Balancing Rules 1. List all elements on both sides of the equation
2. Count the number of atoms for each element on both sides (involves multiplying and adding)
3. Place coefficients to balance equation
***** never change a subscript
4. Re-count the atoms on each side
5. Repeat steps 3 and 4 as needed