Chapter 6 Section 2: Describing Chemical Reactions
I.
What are chemical equations? a.
Is a short, ______ way to show a chemical __________ , using
____________ instead of words. b.
Uses chemical formulas with ___________ and coefficients to _______________ a reaction i.
A formula is a ______________ of symbols that represents elements in the compound ii.
The substances at the ______ of the equation are called
_________ , when the reaction is complete, on the right you have ___________ . iii.
If you have _____________ reactants or products they are separated by a + ______
1.
Reactant 1 + reactant 2 ----> Product 1 + product 2
2.
See figures 7 and 8, page 195
II.
Conversion of mass a.
During a chemical reaction, matter is ________________ nor destroyed, it just changes _______ . b.
All the atoms __________ at the _______ of the reaction are present at the ______ c.
The principle of conservation of mass states that in a chemical reaction, the ____________ of the reactants must
________ the total mass of the products
III.
Open and closed systems a.
Open: matter can ______ from or ________ to the surroundings. i.
Burning match b.
Closed: matter is _____________ to enter or leave the system i.
Eg, reaction is sealed in a plastic bag ii.
See figure 10, page 197
IV.
Balancing Chemical Equations a.
To describe a reaction _____________ , a chemical equation must show the _____________ of each type of _______ on both sides of the equation

b.
4 Step process i.
Step 1: Write the ____________ : Reactants on the Left, products on the right
1.
___H2 + ___O2 ----> ________H20 ii.
Step 2: ________ the number of _______ of each element on each side of the equation
1.
2 hydrogen, 2 oxygen on the react side, 1 oxygen and 2 hydrogen on the product side. ____ THE
ATOMS __________ EQUAL GO TO STEP 3 iii.
Step 3: Use ______________ to balance atoms
1.
A coefficient is a ________ placed in _______ of a chemical formula. It is ___________ by the subscript to get the new number of atoms
2.
Always check _______ sides when using a coefficient
3.
2H2 + 02 ----> 2H2O iv.
Step 4: ________ your work
V.
Classifying Chemical reactions a.
Synthesis: when ____________ elements or compounds combine to make a more ___________ substance i.
2H2 + O2 ----> 2 H2O b.
Decomposition: _____________ compounds into simpler products i.
2H2O2 ----> 2H2O + O2 c.
Replacement: When _____________ replaces another element in a compound or when 2 elements in different compounds
________ places i.
2CuO + C ----> 4 Cu + CO2 ii.
FeS + 2 HCL ----> FeCL2 + H2S iii.
See figure 11, page 200