1. Chapter 8.1: Describing Chemical reactions
What I know about chemical reactions and conservation of matter?

2. Water
How many different ways can you alter the water “physically” and still end up with water?
List the ways you could alter the water “chemically” to create a new substance that is no longer the same as the original substance?

3. Sec 8-1: Chemical reaction
evidence
Heat
Light
Sound
Electrical
temperature change
energy
Gas
Precipitate
Color
Odor
forms

4. Also there are Physical change
Melting points
Density
Condensation
Evaporation
Freezing

5. Example:
determine whether each of the following is a chemical or physical change.
 bending a toothpick
burning a match
burning sugar
making a cake from scratch
smashing a can
melting ice to water

6. How to represent Ch. R. Describe Equations  chemical reactions
Word equation
hydrogen (a gas) + sulfur yields hydrogen sulfide
Formula equation
Symbols (C, Na, and Fe)  elements
Formulas (NaOH) compounds
Equations  chemical reactions

7. Equation Reactants (on the left) Products (on the right)
separated by arrow
included physical states
Examples:
Iron + Oxygen Iron (III) oxide
Methane + oxygen  Carbon dioxide + water

8. Practice Problem
When solid aluminum oxide and hydrogen gas are heated, molten aluminum and water vapor form.
a. Write a word equation for the above reaction.
Aluminum oxide + hydrogen  aluminum + water
b. Write an unbalanced formula equation using all appropriate symbols.

9. To write an unbalanced equation
You must
Write the correct formulas of the reactants and the products.
Indicate physical state by putting a symbol after each formula.
Indicate catalyst by writing its formula above arrow.
Indicate heat and any change above arrow.
Practice Problem: Write an unbalanced equation below word equation.
Methane + oxygen  Carbon dioxide + water