Elements, Mixtures and Compounds

How Atoms are found in Nature

Atoms

Recall that atoms are the building blocks of all matter

• This means matter, such as solids, liquids and gases, are composed of atoms.

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Molecules

When atoms chemically join together they form molecules.

• Molecules can be made up of one type of atom only, e.g. O₂ oxygen or N₂ nitrogen
• These are called elements
• Molecules can be made up of different types of atoms e.g. NaCl salt or H₂O water
• These are called compounds

Atoms continued

Atoms are present in different combinations to form the many different types of matter...

Draw this table (or use the template in Lesson 3) and fill in using the blue text within the following slides. (Take any other notes necessary)

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Elements

• Any material that is composed of only one type of atom is called an element.
• Elements contain one type of atom only
• They can be made up of single atoms (e.g. Helium) or molecules (e.g. oxygen)
• Pure - a single substance
• It is impossible to separate elements (i.e. Helium and other elements cannot be broken down into a simpler substance)
• e.g. oxygen, carbon, mercury

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Elements continued

• The atoms of different elements are different from each other because they have different numbers of protons
• An atom is the smallest particle of any element that still retains the characteristics of that element.
• A piece of an element that we are able to see or handle is made of many, many atoms and all atoms are the same...they all have the same number of protons..

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Elements are found on the periodic table

Compounds

• Compounds, like water, are formed by combining the atoms of different elements together according to some chemical formula
• Compounds contain more than one type of atom/element chemically bonded together
• Pure - a single substance
• It is possible to separate compounds but it is very hard (it takes a lot of energy to break the chemical bonds holding the atoms together in each molecule/compound).
• E.g. sodium chloride (salt), calcium carbonate (limestone)

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Mixtures

• Mixtures are substance with 2 or more substances present together that retain their individual properties
• Mixtures contain more than one type of atom/element
• Impure - a mixture of substances
• It is possible to separate mixtures and it is quite easy (due to different properties of individual substances).
• E.g. air, blood, crude oil, seawater

Atoms-Molecules-Elements-Compounds-Mixtures

• Sodium (S) , Chlorine (Cl), Hydrogen (H) and Oxygen (O) are atoms

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• 2 oxygen atoms combine to form a molecule O₂ (oxygen) which is an element (1 type of atom)
• 2 hydrogen and 1 oxygen combine to form a molecule H₂O (water) which is a compound (more than 1 type atom)
• 1 sodium and 1 chlorine atom combine to form a molecule NaCl sodium chloride (salt) which is a compound (more than 1 type atom)

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• In sea water salt and oxygen dissolve in the water. This forms a mixture of the 3 substances.
• It is a mixture of elements (O₂) & compounds (H₂O & NaCl)

Example Iron and Sulfur

Draw this table (or use the template in Lesson 3) and fill in using the information obtained from our class demonstration or youtube clip.

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Example Iron and Sulfur

• Iron is an element made up of iron atoms
• Sulfur is an element made up of sulfur atoms
• What are their properties?...Test
• Colour?
• Magnetic?
• Float in water?
• If I combine the substances the mix but don't react chemically.
• They still retain their individual characteristics...Test
• If I heat the substances and cause a chemical reaction, the substances bond and form iron sulfide.
• Does it contain the same individual properties?...Youtube