NOTES: 2.2-2.3

Elements, Compounds, and

Mixtures

RECALL…

• MATTER: anything that has mass and

occupies space

Matter

Pure

Substances

Mixtures

Elements

Compounds

Homogeneous

Heterogeneous

PURE SUBSTANCES:

• A pure substance is made of only one

kind of material and has definite

properties.

• EXAMPLES: elements, compounds

What are the Differences Between an

Element and a Compound?

• ELEMENTS – simplest form of matter that

can exist under normal laboratory

conditions

• Elements cannot be separated into simpler

substances by chemical means

• Building blocks for all other substances

• Examples: nitrogen (N2), hydrogen (H2),

and carbon (C)

ELEMENTS (continued)…

• The smallest particle of an element that

has the properties of that element is called

an ATOM.

**Currently we have

about 115 kinds of

atoms. In the natural

world there are 88

different kinds of

atoms.

The others have been

artificially produced in

laboratories.

Making stuff nature

never dreamed of.

The Elements Song

PERIODIC TABLE:

Abundance of the

elements, by

weight

The Earth’s interior is

rich in IRON (Fe)

Sand is made of

silicon & oxygen

The ocean

waters are made

of oxygen &

hydrogen

Atoms are made up of protons,

neutrons, and electrons.

Protons and neutrons are found in

the nucleus of atoms -- roughly at

the center

Electrons travel

around the

nucleus.

Of course real atoms

don’t look anything like

this!

Different kinds of atoms, or elements, are different

because they have different numbers of protons.

They don’t look

anything like this

either!

We list the elements by their

atomic numbers - the number

of protons they have.

Hydrogen, number 1 Helium, number 2

COMPOUNDS

• COMPOUNDS = pure substances that can

be separated into simpler substances only

by chemical means

• made of more than one element bound

together

• Examples: water, table salt, and carbon

dioxide

sodium (Na) chlorine (Cl) Sodium chloride

(NaCl)

CHEMICAL SYMBOLS:

• CHEMICAL SYMBOL – one or two letter

symbol representing an element on the

periodic table

• First letter is always capitalized

• Second letter is always lower case

• Examples:

sodium – Na iodine – I

lead – Pb iron – Fe nickel – Ni

CHEMICAL FORMULAS:

• Chemical formulas: Chemical symbols

and numbers indicating the type and

number of atoms contained in the basic

unit of a substance.

• Examples:

water – H2O

sodium chloride – NaCl

sucrose – C12H22O11

Matter

Pure

Substances

Mixtures

Elements

Compounds

Homogeneous

Heterogeneous

MIXTURES:

• MIXTURE = physical blend of two or more

substances

(that are NOT chemically combined)

• can be classified as:

HOMOGENEOUS or HETEROGENEOUS

Homogeneous Mixture

• Uniform in composition;

• Exhibits identical properties throughout the

mixture;

• Examples: air, salt water, soda water,

solutions, whipped cream, mixture

consisting of one phase

Heterogeneous Mixture

• Not uniform in composition;

• Exhibits portions with different properties;

• Examples: salad, sand, muddy water, oil

and water, soup, granite, soil, mixture

consisting of two or more phases, etc.

How are Mixtures Separated?

Many mixtures can be separated by

simple PHYSICAL means:• Boiling point differences

• Melting point differences

• Particle size

• Density

• Magnetism

• Solubility

• Color

• Smell