Unit 5 Chemical Reactions

Physical Properties

observed and measured without changing the chemical identity of a sample.

Physical properties examples

Luster, elasticity, color, mass

Chemical properties

observed and measured as a sample changes chemical identity.

Chemical properties properties

Flammability, Acidity, Reavactivity

Chemical reactions

energy must be SUPPLIED or ABSORBED to break chemical bonds of reactants. energy is released when new bonds are made.

Chemical change

Alter the chemical composition of the reactant

Chemical change example

Photosynthesis, burning wood, digestion

Sings of chemical changes

change in odor, color, light emission, temperature, and endothermic reactions.

The law of conservation of mass

matter is neither created nor destroyed by chemical reactioons or physical changes

You should use a closed system…

so that you can show that the mass before and after the reaction is the same

Synthesis

two or more substances combine to form a new compound ex-2Na+Cl*2——2NaCl

decomposition

a single compound is broken down into two or more smaller compounds ex-AB——A+B

single displacement

when one element replaces a similar element in a compound ex-AX+B——BX+A

Double displacement

ions from two compounds in a solution exchange positions to produce two new compounds ex-AB+CD——AD+CB

Combustion

The reaction of an element or compound (usually a hydrocarbon) with oxygen tyo form CO*2, water , and heat.

Endothermic Reaction

if more energy is ABSORBED than released

example of Endothermic Reaction

cooking pancakes

Exothermic reaction

if more energy is RELEASED than supplied

examples of Exothermic reaction

handwarmer

Balancing equations

a balanced equation should have an equal amount of atom on each side.