2B.5 Notes Chemical equation 10/16/17

Chemical Changes Remember: Chemical changes (or reactions) occur when a change in matter produces a new substance Color Change Temperature Change Formation of Precipitate Formation of Gas

Chemical Equation A way to represent a chemical reaction using element symbols. Chemical symbols have 2 sides Reactant (Left Side) Product (Right Side) The arrow represents the reaction taking place; The reactant “ yields” or ”makes” 2H + O2  2H2O

Reactant Substances broken apart or combined in a chemical reaction 2H + O2  2H2O

Product New substances formed when a chemical reaction occurs 2H + O2  2H2O

Law of Conservation of Matter The amount of matter does NOT change during a chemical reaction Atoms are rearranged to form new substances This means that the total mass of the reactant is equal to the total mass of the product.

Balanced Chemical Equation Has the same number of each kind of atom on the reactant side as on the product side. To be balanced you have to look at the Subscript and the Coefficient

That means there are 2 Hydrogen Atoms present. Subscript Remember: The subscript is the tiny number behind the element. It tells you home many of that atoms are present 2H2O That means there are 2 Hydrogen Atoms present.

Coefficient The number that comes before the chemical formula and indicates the number of particles present in the reaction. 2H2O That means: H2O + H2O

How do I read a Chemical equation? Chemical Equation: 2H2 + O2  2H2O Multiply the Coefficient in front of the chemical formula by the Subscript 2 x 2 = 4 2H2 + O2  2H2O This means there are 4 Hydrogen Atoms in the Reactant 2 x 1 = 2 2H2 + O2  2H2O1 This means there are 2 Oxygen Atoms in the Reactant

How do I balance a Chemical Equation? Balance Metals Balance Nonmetals (Except Hydrogen & Oxygen) Balance Hydrogen Balance Oxygen

How do I balance a Chemical Equation? Determine if the number of each kind of atom on the left side (Reactant) of the arrow is equal to the number on the right side (Product) of the arrow. H2 + O2  H2O No! Because there is only 1 Oxygen in the Product but 2 Oxygen in the reactant. So I add a coefficient in front of my Product. H2 + O  2H2O

How do I balance a Chemical Equation? H2 + O  2H2O Now there are too many Hydrogen Atoms in the product and not enough in the reactant. So I need to add a coefficient to my reactant. 2H2 + O  2H2O

How do I balance a Chemical Equation? 2H2 + O2  2H2O Is my equation balanced? Yes! There are 4 Hydrogen Atoms in my reactant and 4 Hydrogen Atoms in my product There are 2 Oxygen atoms in my reactant and 2 Oxygen Atoms in my Product.