Classification of Matter

Mixtures, elements, compounds

Scientists like to classify things. One way that scientists classify matter is

by its composition. Ultimately, all matter can be classified as

mixtures, elements and compounds.

Why isn’t it a good idea to classify matter by its phases?

Because one kind of substance can exist in more than one phase – such as H20. And matter changes phases rather easily.

Why isn’t matter classified according to its physical characteristics, such as color?

Scientists wouldn’t find it very useful to group gold, sunflowers, and the sun together.

Composition of Matter Flowchart

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes

Classifying Matter by Composition

Mixtures- are a blend of two or more kinds of matter, each of which retains its own identity and properties. A mixture is mixed together physically. Variable composition, often expressed

by a percent composition by mass or volume (Ex. 5% salt and 95% water

Classifying Matter by Composition

1. Homogeneous – matter with a uniform composition. They are also called solutions. Ex. Salt water and Kool –aid

2. Heterogeneous - matter without a uniform composition

Homogeneous Mixtures

A mixture that appears to be the same throughout.

It is “well mixed.” The particles that make up the mixture

are very small and not easily recognizable.

Examples of homogeneous mixtures

Milk, toothpaste, and mayonnaise are homogeneousmixtures. They are also colloids.

Colloids

In a colloid the particles are mixed together but not dissolved.

The particles are relatively large and are kept permanently suspended.

0

20

40

60

80

100

1st

Qtr

2nd

Qtr

3rd

Qtr

4th

Qtr

East

West

North

Colloids

A colloid will not separate upon standing.

The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy.

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Solutions A solution is a type of homogeneous

mixture formed when one substance dissolves in another.

It is the best mixed of all mixtures. A solution always has a substance that is

dissolved and a substance that does the dissolving.

The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.

Ocean water is a solution

Water as a solvent

Many liquid solutions contain water as the solvent.

Ocean water is basically a water solution that contains many salts.

Body fluids are also water solutions.

Types of solutions

Gas Gas Air (oxygen in nitrogen)

Gas Liquid Soda water (carbon dioxide in water)

Solid Liquid Ocean water (salt in water)

Solute Solvent Example

Solid Solid Gold jewelry (copper in gold)

Metals dissolved in metals are called

alloys.

Air is a solution of oxygen and other gases dissolved in nitrogen

Alloys

Brass is an alloy of copperand zinc.

Stainless steel is a mixtureof iron and chromium.

Classifying Matter by Composition

A heterogeneous mixture is not the same throughout (not uniform).Considered the “least mixed.”Does not appear to be the same throughout.Particles are large enough to be seen and to

be separated from the mixture.

Examples of heterogeneous mixtures Sand and pebbles, gravel, soil, rocks Oil and water, salad, M & M’s, Chocolate cookies.

Granite is a heterogeneous mixture.

Separating MixturesMixtures are separated by their

physical properties. Primary methods of separatingmixtures are:filtrationdistillationcentrifugechromatography

Separating Mixtures

Filtration is a method used to separate the components of mixtures that contain an insoluble solid and a liquid. Example: sand and water

Separating Mixtures

Distillation is a method of separating substances in a mixture by evaporation of a liquid and subsequent condensation of its vapor. Example: desalination of salt water

Separating Mixtures

Centrifuge Used to separate solid-liquid

mixtures such as those in blood. The centrifuge spins rapidly and causes the solid to settle to the bottom.

Ex. Separating blood

Separating Mixtures

Chromatography is a method of separating mixtures that uses a stationary phase and a mobile phase. Paper chromatography can be used to separate pigments because they move at different rates on the paper.

Composition of Matter Flowchart

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes

Classifying Matter by Composition

Pure Substances- A pure type of matter that does not vary from sample to sample. Includes elements and compounds

Classifying Matter by Composition1-Elements- simplest kind of matter, made of one type of atom An atom is the smallest unit of an element

that maintains the properties of that element.

Cannot be broken down into simpler substances by ordinary chemical means

Ex. gold, copper, oxygen (on the periodic table)

Classifying Matter by Composition

2-Compounds – matter composed of the atoms of two or more elements chemically bonded Compounds can be broken down by

chemical methods When they are broken down, the

components have completely different properties than the compound.

Ex. Sugar, salt, water, carbon dioxide

Compounds

Compounds are also pure substances.

But compounds are made from more than one element.

Water is a compound. Water can be broken

down into simpler substances – hydrogen and oxygen.

Classify Itcopper wire, aluminum foil

Classify It Examples:

Magnesium-

Pizza -

Calcium chloride

Orange juice

Club soda

element

hetero. mixture

compound

hetero. mixture

Homo. (solution)

States of matter Solid- matter that can not flow and has

definite volume and shape Liquid- definite volume but no definite

shape and can flow Gas- a substance without definite

volume or shape and can flow. Plasma- a substance that is similar to a

gas, but loses electrons due to its high temperature

States of Matter

Solid

Liquid

Gas

Definite Volume?

YES

YES

NO

Definite Shape?

YES

NO

NO

Particle position and movement

Packed tightly, vibrate about fixed pt

Close together, can move past each other - flow

Far apart, move rapidly - flow