A Matter of FactA Matter of Fact

Mixtures, Elements, Mixtures, Elements, CompoundsCompounds

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

matter is by its matter is by its compositioncomposition.. Ultimately, all matter can be Ultimately, all matter can be

classified as mixtures, elements and classified as mixtures, elements and compounds.compounds.

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

phases?phases?

Because one kind of substance can exist in Because one kind of substance can exist in more than one phase – such as Hmore than one phase – such as H220. Matter 0. Matter changes phases rather easily.changes phases rather easily.

Why isn’t matter classified Why isn’t matter classified according to its physical according to its physical

characteristics, such as color?characteristics, such as color?

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

Scientists ask themselves these Scientists ask themselves these questions?questions? Is the matter uniform throughout?Is the matter uniform throughout? Can it be separated by physical means?Can it be separated by physical means? Can it be separated by chemical means?Can it be separated by chemical means?

By asking these questions scientists By asking these questions scientists can classify matter into:can classify matter into:

Mixtures Mixtures – two or more – two or more substances that are not substances that are not chemically combined with each chemically combined with each other and can be separated by other and can be separated by physical means. The substances physical means. The substances in a mixture retain their in a mixture retain their individual properties.individual properties.

ElementsElements – simplest form of pure – simplest form of pure substance. They cannot be broken substance. They cannot be broken into anything else by physical or into anything else by physical or chemical means.chemical means.

CompoundsCompounds – pure substances that – pure substances that are the unions of two or more are the unions of two or more elements. They can be broken into elements. They can be broken into simpler substances by chemical simpler substances by chemical means.means.

Examples of MixturesExamples of Mixtures Solutions – a special kind of mixture Solutions – a special kind of mixture

where one substance dissolves in where one substance dissolves in another. another.

Suspensions – is made of parts that Suspensions – is made of parts that separate upon standing.separate upon standing.

Emulsions – usually do not mix together Emulsions – usually do not mix together (oil & water for example)(oil & water for example)

Colloids – contain undissolved particles Colloids – contain undissolved particles Alloys – solutions of one or more metals & Alloys – solutions of one or more metals &

other solids.other solids.

Is it uniform throughout?Is it uniform throughout?

If the answer is no, the matter is a If the answer is no, the matter is a heterogeneous mixture.heterogeneous mixture. Considered the “least mixed.”Considered the “least mixed.” Does not appear to be the same Does not appear to be the same

throughout.throughout. Particles are large enough to be seen Particles are large enough to be seen

and to be separated from the mixture.and to be separated from the mixture.

Examples of heterogeneous Examples of heterogeneous mixturesmixtures

Sand and pebblesSand and pebbles Oil and waterOil and water Powdered iron and powdered sulfurPowdered iron and powdered sulfur

Granite is a heterogeneous mixture.

Is it uniform throughout?Is it uniform throughout?

If the answer is yes, the matter is If the answer is yes, the matter is homogeneous (looks the same homogeneous (looks the same throughout).throughout).

That leads us to another question.That leads us to another question.

Can it be separated by Can it be separated by physical means?physical means?

If the answer is yes, the matter is a If the answer is yes, the matter is a homogeneous mixture or solution.homogeneous mixture or solution.

Homogeneous MixturesHomogeneous Mixtures

A mixture that appears to be the A mixture that appears to be the same throughout.same throughout.

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

mixture are very small and not easily mixture are very small and not easily recognizable.recognizable.

Examples of homogeneous Examples of homogeneous mixturesmixtures

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

ColloidsColloids

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

The particles are The particles are relatively large and relatively large and are kept are kept permanently permanently suspended.suspended.

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ColloidsColloids

A colloid will not A colloid will not separate upon separate upon standing.standing.

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

SolutionsSolutions A solution is a type of homogeneous A solution is a type of homogeneous

mixture formed when one substance mixture formed when one substance dissolves in another.dissolves in another.

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

that is dissolved and a substance that is dissolved and a substance that does the dissolving.that does the dissolving.

The substance that is dissolved is the The substance that is dissolved is the solutesolute and the substance that does and the substance that does the dissolving is the the dissolving is the solventsolvent..

Ocean water is a solutionOcean water is a solution

Water is the universal Water is the universal solvent.solvent.

Water as a solventWater as a solvent

Many liquid solutions contain Many liquid solutions contain water as the solvent.water as the solvent.

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

Body fluids are also water Body fluids are also water solutions.solutions.

Types of solutionsTypes of solutions

GasGas GasGas Air (oxygen in nitrogen)Air (oxygen in nitrogen)

GasGas LiquidLiquid Soda water (carbon dioxide Soda water (carbon dioxide in water)in water)

SolidSolid LiquidLiquid Ocean water (salt in water)Ocean water (salt in water)

Solute Solvent Example

SolidSolid SolidSolid Gold jewelry Gold jewelry (copper in gold)(copper in gold)

Metals dissolved in metals are called ALLOYS.

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

nitrogennitrogen

AlloysAlloys

Brass is an alloy of copper and zinc.

Stainless steel is a mixture of iron and chromium.

Can it be separated by Can it be separated by physical means?physical means?

If the answer is no, the matter is a If the answer is no, the matter is a pure substance.pure substance. An elementAn element Or a compoundOr a compound

We’ll talk more about these later in the We’ll talk more about these later in the year.year.