Elements, Mixtures, Compound and Molecules

Element: a substance that cannot be broken down into other substances by chemical or physical means.

C Cu Carbon Copper Chemical Symbols All elements have their own unique symbol. First letter is ALWAYS capitalized. If there is a second letter, it is lowercase. No periods are used in the chemical symbol. C Carbon Cu Copper 3

Mixture: two or more substances that are mixed together but not chemically combined. (can be separated by physical means)

Compound: a substance made of two or more elements chemically combined in a set ratio. (can only be separated by another chemical reaction)

The smallest particle of an element. Atom: The smallest particle of an element.

Molecule: Form when atoms are chemically joined together. The size of the molecule depends on the number of atoms that make it up.

Counting Atoms: Each element in a molecule will have a subscript (smaller number located to the bottom right of the element symbol.) The subscript tells you the number of atoms for that element. Ex= O2 (2 atoms) If the element has no subscript behind it then it is understood to equal 1 atom. Ex=Fe (1 atom) To get the total number of atoms in a molecule, add the subscripts together for the entire molecule. Ex= Fe O2 (3 atoms total)

H= H 2= H2O C6H12O6

2 Types of Molecules: Elements- molecules made of only one type of atom. (Has only one capital letter.) Compounds- molecules that have more than one type of atom. (has more than 1 capital letter.)

Evidence of a Chemical Reaction: Production of a precipitate. Exothermic (gives off heat) or Endothermic (absorbs heat). Production of a gas. (bubbles or vapor) Color change. Odor or smell. Creates a new substance.