Compounds
Mr. McMartin
Beta Science
Vocabulary

Compound: a pure substance composed of two or
more elements that are chemically combined.
Compounds

Made of two or more elements that are chemically
combined.

They combine by undergoing a chemical change or
“reacting.”

A particle of a compound is a “molecule.”

Molecules of compounds are formed when the
atoms of two or more elements join together.
Familiar Compounds
Compound
Elements Combined
Table Salt
Sodium and Chlorine
Water
Hydrogen and oxygen
Vinegar
Hydrogen, carbon, and
oxygen
Carbon Dioxide
Carbon and oxygen
Baking Soda
Sodium, hydrogen, carbon,
and oxygen
Ratio of Elements in a
Compound

Elements don’t randomly join to form compounds.

They join a specific ratio according to their masses

Ex. The ratio of the mass of hydrogen to the mass of
oxygen in water is 1 to 8 or 1:8. This ratio is always the
same.

Every sample of water has a 1:8 mass ratio of hydrogen
to oxygen, if it doesn’t have that ratio… then it is not
water.
Properties of Compounds


Just like elements, compounds have their own
physical properties. These include:

Melting point

Density

Color
Compounds can also be identified by their chemical
properties.

Reactivity

Flammability
Properties: Compounds vs.
Elements

A compound has properties that differ from those of
the elements that form it.


Ex. Sodium Chloride, or table salt, is made of two very
dangerous elements- Sodium & Chlorine.

Sodium reacts violently with water

Chlorine is a poisonous gas.
But when these two elements combine they form
something that is completely safe to eat. It even
dissolves in water without exploding.
Breaking Down Compounds

Some compounds can be broken down into their
elements by chemical changes.

Other compounds break down to form simpler
compounds instead of elements. These can then be
broken down into elements through more chemical
changes.

Ex. Carbonic acid gives pop its “fizz.” When you open
your pop, carbonic acid breaks down into carbon
dioxide and water. These can then be broken down into
carbon, oxygen, and hydrogen.
Methods of Breaking Down
Compounds

The only way to break down a compound is through
a chemical change.

Sometimes energy is needed for a chemical reaction
to take place. There are two ways to do this:

Apply heat and/or apply an electric current
Compounds in Your World

Compounds in Industry


These are usually mined from nature and then made
into the the elements or compounds needed for industry.

Aluminum from aluminum oxide.

Ammonia made from combining nitrogen and
hydrogen
Compounds in Nature

Proteins are compounds found in all living things.

Nitrogen makes proteins

Carbon dioxide- plants use this in photosynthesis