unit 8 chemical reactions and stoichiometry

7 evidence of chemical reaction

unexpected color change, energy gets cold or hot, odor changes, solid is formed unexpectedly, gas produced ( bubbles), irreversible process, new properties

solid

s

liquid

l

gas

g

aqueous

aq

what is a catalyst

a substance formed or process that speeds up the reaction. its written above the yields arrow

how to balance a chemical equation

1. put the inventory straight down under the arrow

2. make odd even if possible

3. how many atoms on each side

4. look at each individual element

5. you can never take away atoms.

synthesis (combination) reactions

happens when 2 or more substances react to form a single product.

balancing hint- least common multiple.

decomposing reactions

a single compound broken into 2 or more products. most require energy to occur.

balancing hint- least common multiple

combustion reaction

oxygen reacts with a substance to release energy, some are also synthesis reactions

balancing hint- least common multiple.

most are reactions with hydrocarbons- combustion method

single replacement reactions

an element replaces one part of a compound

balancing hint- keep polyatomic ions together and balance as a unit

double replacement reactions

exchange between ions between two compounds, no change in charges, may end with a precipitate

balancing hint- keep polyatomic ions together and balance as a unit.