PURE SUBSTANCES AND MIXTURES

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• An element is a substance made up of atoms of one kind.

• A molecule is formed when atoms of the same elements combine.• Two atoms of oxygen combine to form a molecule of oxygen [O

2]

• A compound is formed when atoms or molecules of different elements combine chemically.• Hydrogen and oxygen are combined in a fixed proportion of 2:1 to

form the compound water [H2O].

• Mixtures are two or more substances that are mixed together but not chemically joined.

PURE SUBSTANCE VS. MIXTURE

A pure substance: • made up of 1 type of particle

• ELEMENT= made of 1 type of atomExamples?????

• COMPOUND= made of 1 type of moleculeExamples?????

• cannot be separated into 2 or more substances by physical means

• has uniform composition throughout the whole sample

A mixture: Mixtures are formed by combining two or more pure

substances together without them undergoing a chemical

change.

Therefore, there are two or more substances in the same

space or container.

• can be separated into 2 or more substances by physical or mechanical means

• displays the characteristic properties of the pure substances making it up

• its composition can be varied by changing the proportion of pure substances making it up

Mixtures are different from pure substances

because they contain at least two different

types of particles instead of just one.

There are two different types of mixtures....

When a mixture’s components are easily

recognizable from one another it is called a

HETEROGENEOUS MIXTURE.

You can see different particles. The particles

are not evenly distributed.

Examples: ???

In a HOMOGENEOUS MIXTURE, the parts all look

the same, even though the substances inside still

retain their original properties.

Also known as a solution.

All parts of the mixture look the same. Particles are

evenly distributed.

Examples???

Type of Mixture

Example

gas in gasThe atmosphere is a mixture of gases, mostly nitrogen and oxygen.

liquid in liquid Wine is a mixture of mostly ethanol and water.

solid in solidAlloys, such as brass, are made up of a mixture of metals.

gas in liquidSoft drinks, such as cola, are mixtures of mainly carbon dioxide gas and water.

solid in liquid Sea Water is a mixture of salts dissolved in water.

solid in gasSmoke is mixture of tiny solid particles in atmospheric gases.