Comparing Elements and Compounds

Elements, Compounds and

Mixtures

SC.8.P.8.8 & 8.9

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

Multiple Choice

Two or more elements combined chemically

• Element
• Mixture
• Solution
• Compound

Multiple Choice

Compounds

• have a no definite composition

• Can be broken down by chemical means

• Contains two or more atoms held together by chemical bonds

• Reacts to form NaCl (Salt)

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

Multiple Choice

A Heterogenous mixture

• A mixture that is uniform throughout.
• A mixture with visibly different components.
• A solution with dissolved substances.
• A pure substance without any components.

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.

Multiple Choice

An Acid

• A substance that accepts electrons.
• A solution with a pH above 7.
• A compound that releases hydroxide ions (OH-).
• A substance that donates protons (H+).

Multiple Choice

A Neutralization reaction

• A reaction between two acids that forms a gas.
• A reaction that only produces carbon dioxide.
• A reaction between an acid and a base that produces water and a salt.
• A reaction that involves only solid reactants.