Chemical Equations

Chemical Reactions - OVERVIEW change that occurs when atoms rearrange themselves Can absorb or release energy  Heat  Light  Sound Chemical equations used to describe chemical reactions

What is an equation in math? What does it look like? Chemical equations in science are similar! Think!

Chemical Equation describes a chemical reaction C + O 2  CO 2, The carbon reacts with oxygen to yield carbon dioxide.

Parts of a Chemical Equation This reads “carbon reacts with oxygen react to yield carbon dioxide” C + O 2  CO 2 REACTANTS Molecules that are used in the reaction. PRODUCTS Molecules that are formed in the reaction. The arrow is read as “yields”

Identify the reactants and products: Chemical Equation Name the Elements Name the REACTANTS Name the PRODUCTS 2Na + Cl 2 → 2NaCl Sodium, Chlorine Sodium Chloride (salt) CO 2 + H 2  CH 4 + H 2 O 2H 2 + O 2  2H 2 O 4Al + 3 O 2  2Al 2 O 3 Key: CH 4 = methane, NaCl= Sodium Chloride, Al 2 O 3 = Aluminum Oxide

Law of Conservation of Mass Matter can not be created or destroyed, although it may be rearranged. Lavoisier, 1788

Chemical Equations Because of “ Conservation of Mass”, chemical equations must be balanced Must have same number of each element on both sides of equation Lavoisier, 1788

2H 2 + O 2 2H 2 O  What elements do you have? Balanced or Unbalanced? Hydrogen Oxygen Hydrogen Oxygen A chemical equation must have the same number of atoms of each element on either side of the arrow in order to be balanced

2H 2 + O 2 2H 2 O  How many atoms of each elements do you have? Balanced or Unbalanced? A chemical equation must have the same type and amount of atoms on either side of the arrow in order to be balanced Hydrogen Oxygen Hydrogen Oxygen A chemical equation must have the same type and amount of atoms on either side of the arrow in order to be balanced = 4 = 2 = 4 = 2 BALANCED

Al + Br 2 Al 2 Br 6  What elements do you have? Balanced or Unbalanced? Aluminum Bromine Aluminum Bromine

Balanced or Unbalanced? = 1 = 2= 6 = 2 Al + Br 2 Al 2 Br 6 How many atoms of each elements do you have? Aluminum Bromine Aluminum Bromine *UNBALANCED*

Chemical Reactions & Equations – PRACTICE! K 3 PO 4 + 2HCl  2KCl + H 3 PO 4 Is this equation balanced? K = 3 P = 1 O = 4 H = 2 K = 2 P = 1 O = 4 H = 3 No: K and H are not the same on both sides of the equation Cl = 2 Reactants = Products