A Matter of FactA Matter of Fact

Mixtures, Elements and Mixtures, Elements and CompoundsCompounds

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

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

Why isnWhy isn’’t it a good idea to 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. And 0. And matter changes phases rather easily.matter changes phases rather easily.

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

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

Scientists wouldnScientists wouldn’’t find it very useful to 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 can By asking these questions scientists can classify matter into:classify matter into:

MixturesMixtures – two or more substances that are – two or more substances that are not chemically combined with each other and not chemically combined with each other and can be separated by physical means. The can be separated by physical means. The substances in a mixture retain their individual substances in a mixture retain their individual properties.properties. Solutions – a special kind of mixture where one Solutions – a special kind of mixture where one

substance dissolves in another.substance dissolves in another. ElementsElements – simplest form of pure substance. – simplest form of pure substance.

They cannot be broken into anything else by They cannot be broken into anything else by physical or chemical means.physical or chemical means.

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

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 Considered the ““least mixed.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 It is ““well mixed.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 that is A solution always has a substance that is

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

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

Ocean water is a solutionOcean water is a solution

The universal solvent: The universal solvent: WaterWater

Water as a solventWater as a solvent Many liquid solutions contain water Many liquid solutions contain water

as the solvent.as the solvent. Ocean water is basically a water Ocean water is basically a water

solution that contains many salts.solution that contains many salts. Body fluids are also water solutions.Body fluids are also water 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 copperand zinc.

Stainless steel is a mixtureof 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

ElementsElements Elements are the simplest pure substance.Elements are the simplest pure substance.

An element can not be changed into a simpler An element can not be changed into a simpler substance by heating or any chemical process.substance by heating or any chemical process.

The smallest particle of an element that has The smallest particle of an element that has the properties of that element is called an the properties of that element is called an atom.atom. An atom is the basic building block of matter.An atom is the basic building block of matter.

There are more than one hundred known There are more than one hundred known elements in the universe listed on the elements in the universe listed on the periodic table of elements.periodic table of elements. These elements combine in such a way to create These elements combine in such a way to create

millions of compounds.millions of compounds.

ElementsElements All elements are All elements are

made of atoms.made of atoms. Atoms of the Atoms of the

same element are same element are alike.alike.

Atoms of different Atoms of different elements are elements are different.different.

CompoundsCompounds Compounds are also Compounds are also

pure substances.pure substances. But compounds are But compounds are

made from more made from more than one element.than one element.

Water is a Water is a compound.compound.

Water can be broken Water can be broken down into simpler down into simpler substances – substances – hydrogen and hydrogen and oxygen.oxygen.