Chemical Formulas The chemical formula for Aspirin = C 9 H 8 O 4 Formulas show two things: 1.The elements in a compound and 2.The ratio of the different atoms that make up that substance.

Chemical Formulas Are Convenient The chemical formula for a molecule of Aspirin is C 9 H 8 O 4 It would take a lot of writing to express this in words. Nine carbon atoms combined with eight hydrogen atoms combined with four oxygen atoms. C 9 H 8 O 4 is a much more convenient and short way to write the aspirin molecule.

Chemical Equations Scientists use a shortcut for showing chemical reactions. It is called a Chemical Equation

Chemical Equations This is a chemical equation. 2H 2 + O 2  2H 2 O HydrogenOxygenYieldsWater Coefficient Subscript ReactantsProducts

In the molecular compound H 2 O, the number two is called a ________________. subscript

How many atoms does the molecule H 2 O have? 3

What are the names for the substances before a chemical reaction? _________________ reactants

What are the names for the substances after a chemical reaction? The products

During a chemical reaction matter is not created nor destroyed. This principal is called Conservation of Mass. This means there will be the same number of atoms at the end of a reaction as there were at the beginning of the reaction. Conservation of Mass

Conservation of Mass Example Read about conservation of mass on pages 154 and 155. Go to the “Out” section of your notes to answer the questions below. 1.What example was used to explain conservation of mass? 2.How does this example demonstrate conservation of Mass?

During a chemical reaction matter is not created nor destroyed. This principal is called _________________________. Conservation of mass

The number placed at the front of an element or compound as seen in red below is called a ___________________? 2 SO 2 coefficient

Is This a Balanced Equation? H 2 + O 2  H 2 O No! There are 4 atoms on the reactant (left) side of the equation and 3 atoms on the product (right) side?

Can you balance this equation by adding a subscript? Why or why not? H 2 + O 2  H 2 O No! Subscripts cannot be added to balance an equation. You can only add coefficients. H 2 + O 2  H 2 O2 2

The number of reactants and products can ______________.

What is it called when the same number of atoms exist on both sides of a chemical equation? The equation is said to be ______________________.

1. Synthesis (When two or more reactants combine.) Example: Three Types of Reactions 2SO 2 + O 2 + 2H 2 O  2H 2 SO 4 2. Decomposition (When reactants break down into simpler products) Example: 2H 2 O 2  2H 2 O + O 2 3. Replacement (When one element replaces another in a compound, or when two elements in different compounds trade places. Example: 2CuO + C  2Cu + CO 2

What type of reaction would this be? 2 SO 2 + O 2 + 2H 2 0 2H 2 SO 4 This is a Synthesis Reaction

What type of reaction would this be? 2NH 4 NO 3 2N 2 + O 2 +4H 2 O This is a Decomposition Reaction

What type of reaction would this be? P 4 O H 2 O 4H 3 PO 4 This is a Replacement Reaction

What type of reaction occurs when an airbag inflates? A Decomposition reaction in which a lot of nitrogen gas is created to quickly fill the airbag.