Comparing Elements and Compounds

ELEMENTS & COMPOUND

Elements (Pure Substance) are the building blocks of matter, and cannot be
broken down without a loss of their properties.

Example, Hydrogen and oxygen are elements that cannot be broken down into
other elements.

Compound: Two or more elements combined chemically

Compounds have 3 important characteristics:

1.

Definite composition (Predictable ratio)

2.

Properties are different from those of the individual elements

3.

Can be broken down into simpler substances by chemical means

Example: Water is a compound that can be broken down into Hydrogen and
Oxygen

MOLECULES

A Molecule is a group of two or more atoms held together by chemical bonds.

NOTE: ALL molecules are not compounds; ALL compounds are molecules

Pure substance

-Contains ONLY one type of molecule

-Is composed of either one type of element or one type of molecule

CHEMICAL FORMULA

Chemical Formula uses chemical symbols and subscripts to identify the number
of atoms of each element in a molecule of a compound.

MIXTURES

Mixture is matter made up of two or more substances that combine without joining
together chemically. Each substance keeps its own properties and can be
separated.

NOTE: Every pure compound or pure element are known as a substance

There are two type of Mixtures:

1.

Heterogenous Mixture: Substances that are not distributed evenly
throughout the mixture

2.

Homogeneous Mixture: All substances are evenly

distributed

SOLUTIONS

Solutions is a homogenous mixture that contains two or more pure substances
distributed uniformly throughout

TWO Parts of a Solution

1.

Solvent: Is the substance that does the dissolving

2.

Solute: Is the substance that dissolves

WHAT IS AN ACID

Acids is any substance that releases hydrogen ions (H+) in solution.

-Properties of acid: Taste sour, releases H+ ions, reacts with metal (Corrosive),
irritate skin, pH < 7, turns blue litmus paper red.

WHAT IS A BASE

Base is any substance that releases hydroxide ions (OH-) in solution

-Properties of base: Taste bitter, forms a hydroxide when it dissolves in water,
feel slippery to the touch, makes skin burn and feel itchy, pH > 7, turns red
litmus paper blue

NEUTRALIZATION REACTION

Neutralization reaction is a chemical reaction in which an acid and a base mix,
reacts chemically, and forms both water and a salt.

pH SCALE

Determine if a substance is an acid or base by measuring its pH and comparing it
to a pH scale.