Unit 1 – Chapter 3 Notes

Mr Nelson

The Properties of Matter

Matter: The “stuff” that makes up the universe Has mass and volume

All matter is made up of tiny particles called atoms

Elements and Compounds

There are over 100 different kinds of atoms

We call these different types of atoms different elements All matter is made up of different

combinations of elements

Molecules A molecule is made of atoms that are

“stuck” together

Smallest part of a compound that has properties of that compound

Can be the same atoms

Compounds Compounds: substances made by

bonding atoms together in specific ways.

Two or more different types of atoms bonded together

A compound has the same particles throughout

Pure Substances Pure substances always have a definite

composition

Elements

Specific Compounds

They are not generic (Orange Juice)

Physical vs. Chemical Properties

Chemical Properties: examples are:

Rusting, not reacting, fermentation, combustion

You must perform a chemical reaction to test chemical properties (and then you change the substance!)

Physical vs. Chemical Properties

Physical properties: examples are:

Odor, color, volume, solid, liquid, or gas, density, melting point, boiling point

You can test physical properties without changing the substance

Intensive vs Extensive Properties

Extensive Depend on how much substance

Mass, length, volume

Intensive Inherent quality of substance

Density, odor, color

Chemical and physical changes

Physical changes – don’t affect the composition of the substance Involves physical properties Solid liquid gas

Chemical changes – a given substance is changed to another substance Silver tarnishing Leaves growing from soil, water, and air

Which is which? Iron is melted

Iron combines with oxygen to form rust

Wood burns in air

A rock is broken in to small pieces

Milk turns sour

Wax is melted

Wax catches on fire

A bee stings you and you swell up

Mixtures and Pure Substances

A mixture is something that has variable composition Wood – varies depending on the tree it is cut

from

Soda – contains lots of dissolved substances (CO2, sugar)

Air – contains lots of different substances in different amounts, depending on where you are.

Substances in the air N2 = 78.08%

O2 = 20.95%

H2O = depends on humidity

Ar = 0.93%

CO2 = 0.033%

Ne = 0.0018%

He = 0.00052%

Compounds vs. Mixtures The air is not the same everywhere

Florida’s air is probably not the same as Death Valley’s air!

Gold Pure gold is too soft and “bendy” (the scientific

word is malleable) to be useful We mix it with silver and copper to strengthen it Mixtures of metals are called Alloys

Compounds vs. mixtures Remember – a compound has particles that

are ALL THE SAME A mixture has different compounds/elements

in different proportions

Is this an example of a mixture or a compound?

Pure substances A pure substance always has the same composition

Pure substances can be elements or compounds

Mixtures can be separated in to pure substances:

MixturesTwo or more pure substances

Types of mixtures Homogeneous mixtures: the mixture is the

same throughout Gatorade Salt water These are also called solutions

Heterogeneous mixtures: some regions have different properties than others (not uniformly mixed) Sand in water Dirt

Which is which? Gasoline

A stream with gravel at the bottom

Maple syrup

Oxygen and helium in a scuba tank

Air

Brass

Copper metal

Sodium chloride (salt)

Law of Definite Proportions Compounds are always composed of

the same elements. Table salt is always sodium chloride,

otherwise it is something else

Example: A 58.5 gram sample of Table Salt is composed of 23.0g of Sodium.

What mass % is sodium & chlorine?

Law of Multiple Proportions When different compounds are formed

by the combination of the same elements the mass ratio of the two elements of the different compounds is a whole number.

Hydrogen and Oxygen – 2 compounds

H2O H2O2

Mass % of element in one compound compared to % mass of same element in a different compound is always a whole number ratio.

Law of Multiple Proportions Example: Iron combines with oxygen in

different ratios FeO & Fe2O3

In a 100g sample of each

In compound 1 Fe is 77.7g of the compound In compound 2 Fe is 69.9g of the compound

Find the whole number ratio of the mass %’s?Which compound is which? (Hint: definite prop)