Matter and Change

Chemistry is…

Chemistry:

Is the study of the

composition, structure,

and properties of matter

and the changes it

undergoes

Reactants Products

C2H5OH + 3 O2 2 CO2 + 3 H2O + Energy

Reactants Products

Matter

Anything that has mass and occupies space

MassA measure of the amount of matter

Any property that describes physical attributes of a substance:• Color• Phase• Aroma• Mass• Length• Height• Ductility• Malleability• Conductivity• Boiling point• Melting point

Types of Physical Properties of Matter

Extensive properties

Intensive properties

Volume

Mass

Energy Content

depend on the amount of matter that is present.

do not depend on the amount of matter present.

Melting point

Boiling point

Density

Describes the chemical nature of a substance:• Reacts with oxygen

• Decomposes to produce a gas

• Oxidizes

• Is a reducer

• Reacts with sulfur

Chemical ChangeA change in which one or more substances are converted into different substances.

Heat and light are often evidence of a chemical change.

Production of Light

Unexpected color change

Production of heat

Formation of a precipitate

Liberation of a gas (w/out

heating)

Physical Change

A change in a substance that does not involve a change in the identity of the substance.

Example:

Phase Changes: A substance changing state from a solid to a liquid to a gas.

The same substance remains after the change

Examples of Physical Change:• Pounding

• Cutting

• Heating

• Dissolving into a solution

• Melting

• Boiling

Phase Differences

Solid – definite volume and shape; particles packed in fixed positions.Liquid – definite volume but indefinite shape; particles close together but not in fixed positions.

Gas – neither definite volume nor definite shape; particles are at great distances from one another.

Plasma – high temperature, ionized phase of matter as found on the sun.

Three Phases

Elements

Compounds

AtomThe smallest unit of an element that maintains the properties of that element

ElementA pure substance made of only one kind of atom

CompoundA substance that is made from the atoms of two or more elements that are chemically bonded.

Sucrose – C12H22O11

Sucrose is also known as table sugar!

Two or more substances physically combined. A mixture can be either heterogeneous or homogeneous.• Heterogeneous: A mixture of two or more substances with

visible interfaces Example: A bowl of peas and carrots

• Homogeneous: A mixture of two or more substances with no visible interfaces Example: Brass – a mixture of copper and nickel

Solution: A special type of homogenous mixture in where the particles are actually dissolved on the microscopic level Example: sugar water

The constituents of the mixture retain their identity and may be separated by physical means.

Mixtures

Can it be physically

separated?

Element CompoundHeterogeneous

Mixture

no yes

Is the composition

uniform?noyes

Can it be chemically

decomposed?yesno

Homogeneous

Mixture

MIXTUREPURE SUBSTANCE

MATTER

Element

• composed of identical atoms

• Ex:

copper wire

aluminum foil

Compound

• composed of 2 or more

elements in a fixed ratio

• properties differ from those

of individual elements

• Ex:

table salt (NaCl)

Law of Definite Composition

• A given compound always contains the same, fixed

ratio of elements.

Law of Multiple Proportions

• Elements can combine in different ratios to form

different compounds.

For example…

Two different compounds,

each has a definite composition.

Carbon, C Oxygen, O Carbon monoxide, CO

Carbon Dioxide, CO2Oxygen, OOxygen, OCarbon, C

Variable combination of 2 or more pure

substances.

Heterogeneous Homogeneous

Tyndall

Effect?no yes

Will mixture separate if

allowed to stand?yesno

Suspension (course solid in liquid) Emulsion (liquid in liquid)

Colloid

Suspension, Colloid, or EmulsionSolution

Homogeneous

Mixture (Solution)

Solid or liquid

particles?liquidsolid

Suspension or Emulsion

Solution

• homogeneous

• very small particles

• no Tyndall effect

• particles don’t settle

• Ex:

rubbing alcohol

Colloid

• homogeneous

• very fine particles

• Tyndall effect

• particles don’t settle

• Ex:

milk

Suspension

• homogeneous

• large particles

• Tyndall effect

• particles settle if

given enough time

• Ex:

Pepto-Bismol

Fresh-squeezed

lemonade

Emulsion

• homogeneous

• mixture of two

immiscible liquids

• Tyndall effect

• particles settle if

given enough time

• Ex:

Mayonnaise

Examples:

graphite

pepper

sugar (sucrose)

paint

coffee

-element (C)

-hetero. mixture

-compound

-suspension

-solution

The components of dyes such as ink may be separated by paper chromatography.

Separation of a Mixture

Separation of a Mixture

Distillation

Separation of a Mixture

Filtration

Separation of a Mixture

Evaporation

Magnetic

Separation

Decantation

Separation of a Pure CompoundThe Electrolysis of water

Water Hydrogen + Oxygen

H2O H2 + O2

Reactant Products

Compounds must be separated by chemical means.

With the application of electricity, water can be separated into its elements