Molecules and Compounds

Compound Formed from 2 or more elements in a specific proportion When combined, new properties are created They contain 2 or more different elements Examples: H 2 0, NaCl, CO 2

Molecule A molecule is the smallest unit of a compound They are made up of 1 or more elements The elements can either be the same or different Examples: O 2, O 3, H 2 O, CO 2

So… All compounds are molecules, BUT not all molecules are compounds. Why?

Chemical Formulas Scientists use chemical formulas to write the name of compounds It is a combination of numbers ( subscripts and coefficients) and symbols The subscript (small number) indicate how many of each atom are present The coefficient (larger number) indicate how many of each molecule is present

Example C 3 H 8 O is the chemical formula for rubbing alcohol. There are ___carbon, ___ hydrogen, and 1 oxygen atom that make up one molecule of alcohol.

Example NaCl is the chemical formula for salt There is ____ Na atom and ____ Cl atom

Example NH 3 is the chemical formula for ammonia There is ____ N atom and _____ H atoms

Example 4CO 2 How many C and how many O?

Example Cont. Think about it like a math problem- 4 X (CO 2 ) So there are ____ C atoms and ____ O atoms

Example 6H 2 O There are ___ H atoms and ____ O atoms

Example 3C 6 H 12 O 6 There are ____ C atoms, ____ H atoms, and ____ O atoms

Chemical Equations Chemists way of showing a chemical reaction with elements Reactant yields the product The arrow means “yields” Must be balanced (must have the same number of elements on both sides)

Chemical Equations

Important thing to remember is the law of conservation of matter If there are 4 carbons on one side, there must be 4 on the other side because matter can not be created or destroyed