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Elements Compounds Elements Compounds and Mixturesand Mixtures

11/04/23Element, mixture or Element, mixture or compound?compound?

Salty water Hydrogen

Hydrochloric acid

Sodium chloride (salt)

Diamond

Air

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Is it an element, compound or Is it an element, compound or mixture?mixture?

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

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

classified as mixtures, elements and compounds.

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

state?state?

• Because one kind of substance can exist in more than one state – such as H20. And matter changes phases rather easily.

• Remember Topic 3 – The World of Chemistry

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What is an element?What is an element?

• An element is a pure substance that cannot be broken down into simpler substances.

• A pure substance is a substance in which there is only one type of particle.

• An element is a chemical that contains only one type of atom.

• Pure gold is an element because it contains gold atoms only.

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All the elementsAll the elements are found on are found on thethe

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What are atoms?What are atoms?

• All chemicals are examples of matter.

• All matter is made up of extremely small particles called atoms.

• Learn more about atoms in LO 4

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What are compounds?What are compounds?A compound is a substance that contains different elements (different atom types) chemically joined together

Here are some examples:

Glucose

Methane

Sodium chloride (salt)

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CompoundsCompounds

• A compound is a pure substance composed of two or more elements that are chemically joined together.

• Compounds are new substances produced by chemical reactions. To be chemically combined, the elements in the compound need to have reacted with one another.

• Most elements are not found alone in nature, but rather combined with other elements. Most substances you encounter are compounds!

• A compound has fixed proportions of the different elements. Eg. water

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Glucose is a compoundGlucose is a compound

Containing the elements:•Carbon

•Hydrogen•oxygen

CC66HH1212OO66

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What are molecules?What are molecules?

• Molecules are groups of atoms joined together.

• The compound water is a molecule containing 2 hydrogen atoms joined to an oxygen atom.

• The element oxygen forms molecules of oxygen gas = O2

Oxygen molecules

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MixturesMixtures

• A mixture is a combination of two or more substances that are not chemically combined.

• When you mix up chemicals and no new substance is produced then a mixture is formed.

• Substances in a mixture retain their identity, they do not change into something else.

• Mixtures can be physically separated through physical change. Eg: picking the pecans out of pecan pie, boiling salt water to evaporate the water and leave the salt.

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AirAirAir is a mixture…which can be separated – see LO 8

79% 79%

21% 18%0.03%

1%

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Classification of Matter Classification of Matter Overview Overview

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Test yourselfTest yourself

Is it an element, compound or mixture?

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(Gas)

One Element The Same Element(Solid)

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This one likes to go round in pairs as a

gas (molecules)

Another element A mixture of two elements

11/04/23This is not a mixture, it is a

COMPOUND of two different elements

This is just a mixture of two

elements

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Element, Compound or

Mixture ?

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Element, Compound or

Mixture ?

Element

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Element, Compound or

Mixture ?

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Element, Compound or

Mixture ?

Element

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Element, Compound or

Mixture ?

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Element, Compound or

Mixture ?

Mixture

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Element, Compound or

Mixture ?

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Element, Compound or

Mixture ?

Compound

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Element, Compound or

Mixture ?

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Element, Compound or

Mixture ?

Compound

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Element, Compound or

Mixture ?

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Element, Compound or

Mixture ?

A mixture of a compound and

an element

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What do we call these things?

6 Atoms which happen to be of 3 different elements

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What do we call these things?

A Molecule

Yes, it also happens to be 2 atoms joined

together but we don’t call it “2 atoms joined together” we say it is

one molecule

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What do we call these things?

A Molecule of a compound

2 molecules of a compound