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 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. And 0. And matter changes phases rather easily.matter 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 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 substances in a mixture retain their individual properties.individual 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.

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.

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.

Examples of homogeneous Examples of homogeneous mixturesmixtures

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

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.

ElementsElements

In 1813, a system In 1813, a system of representing of representing elements with elements with symbols was symbols was introduced.introduced. Each symbol consists of one Each symbol consists of one

or two letters.or two letters. Two letters are needed for Two letters are needed for

a chemical symbol when a chemical symbol when the first letter of that the first letter of that element’s name has element’s name has already been used.already been used.

Common ElementsCommon Elements

AluminumAluminum AlAl

BromineBromine BrBr

CalciumCalcium CaCa

CarbonCarbon CC

GoldGold AuAu

HeliumHelium HeHe

HydrogenHydrogen HH

NitrogenNitrogen NN

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.