1. Balancing Equations
Unit 5 Lesson 1
Demos
It is Eggothermic

2. Chemical Reactions
A chemical reaction is a process in which physical and chemical properties of the original substance change as existing bonds are broken and new bonds are formed giving new substances with different physical and chemical properties.

3. Evidence of Chemical Rxns
Temperature Change
Energy released or absorbed (heat, light)
Color change
Gas formation
Appearance of a solid (precipitate)
Formation of water

4. Reactants and Products
Reactants are the substances you consume in a reaction
Products are the substances that you produce in a reaction
HCl + NaOH  H2O + NaCl
Reactants Products

5. calcium + oxygen  calcium oxide
Chemical Equations
Word Equations
calcium + oxygen  calcium oxide
Formula (skeleton) Equations
Ca + O2  CaO

6. Balancing Equations 3Mg + N2  Mg3N2
Law of Conservation of Matter indicates that the number of atoms of each type of element must be the same in the reactants and the products
A coefficient is the number placed in front so that reactants equal products
Coefficients may only be placed in front of the molecules/elements (you cannot change subscripts)
Subscripts need to be determined before the equation can be balanced
Reactants must equal products. The Law of Conservation of Matter must be fulfilled.
3Mg + N2  Mg3N2

7. Steps for Balancing Products Reactants 1 C 1 C 2 H 4 H 3 O 2 O
1. Write the equation. CH4 + O2  CO2 + H2O 2. Do an atom inventory.
Products
1 C
2 H
3 O
Reactants
1 C
4 H
2 O

8. Reactants 1 C 4 H 4 O Products 1 C 4 H 4 O
3. Add coefficients to make the equation balance. CH4 + ___O2  CO2 + ___H2O 4. Check your answer. 2 2
Reactants
1 C
4 H
4 O
Products
1 C
4 H
4 O
Balance oxygen last and hydrogen second to last.

9. Sample Problem 1 ____Al + ___O2  ___Al2O3 4Al + 3O2  2Al2O3
Write a balanced chemical equation for the reaction in which aluminum reacts with oxygen to produce aluminum oxide.
____Al + ___O2  ___Al2O3
4Al + 3O2  2Al2O3

10. Sample Problem 2 2HCl + CaCO3  CaCl2 + H2O + CO2
Write a balanced chemical equation for the reaction in which hydrochloric acid reacts with calcium carbonate to produce calcium chloride, water, and carbon dioxide.
_HCl + _CaCO3  _CaCl2 + _H2O + _CO2
2HCl + CaCO3  CaCl2 + H2O + CO2

11. Samples __BeF2 + __ Al2O3  __ BeO+ __ AlF3
__PbO + __HCl  __H2O + __PbCl2