Elements, Compounds and Mixtures

Elements, Compounds, Mixtures

Ultimately, all matter can be classified as mixtures, elements and compounds

Questions to ask to help classify! Is the matter uniform throughout? Can it be separated by physical

means? Can it be separated by chemical

means?

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.

Elements Elements are pure substance that

cannot be separated into simpler substance by physical or chemical means.

Compounds

Pure substance composed of two or more different elements joined by chemical bonds.

Made of elements in a specific ratio that is always the same Has a chemical formula Can only be separated by chemical means, not physically

H2O

CO2

NaCl

Compounds

Water is a compound.

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

Mixtures A combination of two or more pure

substances that are not chemically combined.

substances held together by physical forces, not chemical

No chemical change takes place Each item retains its properties

in the mixture They can be separated physically

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Heterogeneous Mixtures

Does not appear to be the same throughout.

Particles are large enough to be seen and to be separated from the mixture sometimes by filtering.

Examples of heterogeneous mixtures

Sand and pebbles Chicken noodle soup Granite Oil and water

Homogeneous Mixtures

A mixture that appears to be the same throughout.

The particles that make up the mixture are very small and not easily seen

Cannot be separated by filtering Some examples: salt water solution,

kool aid, ice tea mix and water

Suspensions

Are mixtures in which the particles are larger than ones found in solution. They are insoluble

( they don’t dissolve) and will settle out if left alone. They are heterogeneous.

Examples: blood, oil and water, muddy water, snow globe, glitter and water

They also do not transmit light they scatter light or block light.

Can be separated by filtering

Colloids

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

The particles are relatively large and are kept permanently suspended.

Cannot be easily filtered

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Examples of Colloids

milk, mayo, cheese, whipped cream, deodorant, fog, gelatin,

smoke, toothpaste

detergents They are

homogeneous mixtures

•

Solutions

A solution is a type of homogeneous mixture formed when one substance dissolves in another.

A solution always has a substance that is dissolved( the solute) and a substance that does the dissolving. ( the solvent)

The universal solvent: Water

Types of Solutions

Dilute-less solute than solvent.

Concentrated Saturated- A solution which has as

much solid dissolved in it, as it possibly can contain.

Concentration- the amount of a particular substance in a given quantity of a mixture

Solubility-the ability of one substance to dissolve in another at a given temperature and pressure

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 Brass ( copper and zinc)

.

Air is a solution of oxygen and other gases dissolved in

nitrogen

Alloys are Mixtures

Alloys are solid solutions of metals or nonmetals dissolved in metals.

Alloysexamples

)

Brass is an alloy of copperand zinc.

Stainless steel is a mixtureof iron and chromium.