Chapter 7
Chemical Reactions
7.1 Describing Chemical Reactions
What is a chemical reaction?
Demos
Chemical Reaction: is when a substance undergoes a chemical change to produce a
new substance or substances
7 different types of chemical reactions
Chemical equations: are used to represent a chemical change/reaction
Ex.
2 H2 + O2  2 H2O
Reactants: are the substances that undergo chemical change (bonds broken)
(ingredients)
Products: are the new substances produced by the change (new bonds made) (cookies)
Reading Chemical equations
+ sign = “reacts with”
 sign = “to produce”
Element symbols = moles of that element
Coefficient = # of moles
Law of conservation of mass:
states that mass is neither created nor destroyed in a
chemical reaction
By ordinary means, we can’t make or destroy matter
ONLY REARRANGE IT!!!!!!!!
Balancing Equations
When writing chemical equations, the law of conservation of mass must be followed.
We must have the same amount of each element on both sides of the equation
Coefficients: are used to show proportions of reactants and products)
PERFECT PRACTICE,
MAKES PERFECT!!!!!!