NOTES: 2.2-2.3 Elements, Compounds, and Mixtures.

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