Presentation on theme: "Chapter 8.1: Describing Chemical reactions What I know about chemical reactions and conservation of matter?"— Presentation transcript:
Chapter 8.1: Describing Chemical reactions What I know about chemical reactions and conservation of matter?
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?
Sec 8-1: Chemical reaction evidence energy forms Heat Light Sound Electrical temperature change Gas Precipitate Color Odor
Also there are Physical change Melting points Density Condensation Evaporation Freezing
Example: determine whether each of the following is a chemical or physical change. 1. bending a toothpick 2.burning a match 3.burning sugar 4.making a cake from scratch 5.smashing a can 6.melting ice to water
How to represent Ch. R. Describe Word equation Formula equation Symbols (C, Na, and Fe) elements Formulas (NaOH) compounds Equations chemical reactions hydrogen (a gas) + sulfur yields hydrogen sulfide
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
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.
To write an unbalanced equation You must 1. Write the correct formulas of the reactants and the products. 2. Indicate physical state by putting a symbol after each formula. 3. Indicate catalyst by writing its formula above arrow. 4. Indicate heat and any change above arrow. Practice Problem: Write an unbalanced equation below word equation. Methane + oxygen Carbon dioxide + water