What are the 2 types of pure substances?

Elements

Compounds

Elements are the simplest substances.

Elements CANNOT be separated into simpler substances through any

chemical reaction or physical change.

If the substance is an element, the smallest particle is an

ATOM.

Sulfur

What is sulfur’s atomic number?

16Elements are identified

by their atomic numbers. (Number of protons)

Compounds are formed when elements are

chemically bonded in a definite ratio.

Compounds CAN be separated into simpler substances through chemical reactions.

How can you tell the difference between elements and compounds if

you are told their names?Elements will be found directly on

the PERIODIC TABLE OF THE ELEMENTS while compounds are NOT directly

found on the table, but are two or more

elements combined. (Ex: H2O

– H and O.)

HINT: Every element is either abbreviated with a single CAPITAL letter (H) or one CAPITAL letter and one

lowercase letter (Li). Therefore, when you are trying to decide if

a substance is an element or compound – count the capital

letters!

Decide if the substances listed on your notes are elements or compounds.

Hint: Only two of the substances are elements.

compound

compound

compound element

element

compound

Mixtures are formed when substance are placed together

which will not chemically react.Mixtures CAN be separated based on the physical

properties of the substances in the mixture.

Iron and Sulfur mixed together.

There are two main categories of mixtures.

Heterogeneous Mixtures Homogeneous Mixtures

The substances within the mixture are distinct and easily identified.

The substances within the mixture are blended

evenly together.

Mixtures are NOT formed with any kind of definite ratio. While brass is a mixture of

copper and zinc, there is not an exact recipe and different manufacturers will use a

slightly different percentage of each metal.

BrassCopper

Zinc

SolutionsSolutions one of the most common forms of

mixtures. They are created when substances are evenly mixed together.

Solution = Homogeneous Mixture

Aqueous solutions are formed with

solutes are dissolved in water

Alloys are formed when metals are

evenly mixed together.

Gaseous solutions, like air, formed when gases mix

together.

Important Fact: An alloy is made when metals are mixed together.

The metals are melted together and mixed. They can be separated by melting the alloy. When a solid

has melted completely into a liquid, we say that it is molten.

Is melting a physical or chemical change?

Melting is a physical change. This means that alloys are NOT a new substance. They are

simply a mixture of substances.

Common Alloys

Steel(Iron and Nickel

Alloy)

Brass(Copper and Zinc Alloy)

Bronze(Copper and

Tin Alloy)

Let’s take a look at a few different ways to separate mixtures:•Sifted/filtered•Magnetism•Distillation•Separatory Funnel (density)

While volume, sometimes simply referred to as size and shape, is related to the size of a sample and it can be used to separate a substance from a heterogeneous mixture. If one substance is in larger pieces than the other, the larger substance can be sifted or filtered from the mixture.

Some elements can be separated from heterogeneous mixtures based on the physical property of magnetism. In particular these elements are iron, cobalt, and nickel. Together these elements are known as the Iron Triad.

Distillation is a process that is used to separate a liquid

from a homogeneous mixture based on

differences in boiling point.

1. Water is evaporated from the solution2. The evaporated water is cooled and condenses back into a liquid3. The pure, distilled water is collected.

Distillation

Distillation can also be used to separate two liquids which

have been dissolved together. Liquids that can be evenly mixed together are known as miscible liquids. Miscible liquids are either

both polar or both nonpolar.

Oil and water are immiscible because one is polar and the other in nonpolar.

Oil

Water

Based on this picture, which liquid is more dense: oil or water?

Immiscible liquids can be separated very

easily using a device known as a separatory

funnel. Notice that this device also

separates heterogeneous

mixtures based on the property of density.