1. Chemistry of Living Things
Day 3: Chemical Formulas

2. .
Chemical Formulas
A chemical formula represents the chemical makeup of a compound.
It shows the numbers and kinds of atoms present in a compound.
It is a kind of “shorthand” that scientists use.

3. Formula Examples H2O (water) -Two Hydrogen, One Oxygen
The chemical formula for sugar is C6H12O6
This means that in one molecule of sugar there are six carbon atoms, twelve hydrogen atoms and six oxygen atoms.
H2O (water) -Two Hydrogen, One Oxygen
SO2 (sulfur dioxide) -One Sulfur, Two Oxygen
CO2 (carbon dioxide) -One Carbon, Two Oxygen

4. Structural Formulas
A formula can also show the kinds, numbers, and arrangement of atoms.
This is called a structural formula.
Here is the structural formula of Hydrogen gas.

5. Equations Equations are used to describe chemical reactions.
The substances that start the reaction are called the reactants.
The reactants are placed on the left side of the equation.
The substances formed by the reaction are called the products.
The products are placed on the right side of the equation.
The arrow means “to make” or “to form”.

6. EXAMPLE
REACTANT + REACTANT PRODUCT

7. Equations C6H12O6 + O2  6H2O + 6CO2
Reactions may be represented either by words or formulas.
The word equation for aerobic respiration is:
(enzymes)
SUGAR + OXYGEN  ENERGY + CARBON DIOXIDE + WATER
An equation using formulas instead of words is called a chemical equation.
The chemical equation for aerobic respiration is:
C6H12O O2  6H2O + 6CO2

8. Check It…
This Number Represents the Number of ATOMS in the molecule. There are TWO ATOMS of Hydrogen in one molecule of Water!
This Number Represents the Number of MOLECULES present. So this means there are SIX MOLECULES of Water!

9. So…
IS THE SAME AS:

10.  IMPORTANT! Equations must have same number of Atoms on Both Sides!
C6H12O O2  6H2O + 6CO2 C 6  H 12 O 8

11. This is how it’s done!

12. Practice: Page 28 Two Oxygen? Two Hydrogens and One Oxygen?
Six Molecules of #2?
One Carbon and Two Oxygen?
Six Molecules of #4
Six Carbon, Twelve Hydrogen, and Six Oxygen?
Three Cheeseburgers?