Elements, Compounds and Mixtures

By Miss Buicke.

Elements Mixture Compounds

What we must know from the syllabus:

OC12

Compare the properties of the simple compounds to those of the constituent

elements

OC13

Compare mixtures and compounds made from the same constituents,

OC3

Understand what an element is and recall that all known elements are listed in

the Periodic Table; understand what a compound is and what a mixture is; recall that when

elements combine to form compounds they may lose their individual properties

Elements:An element is a substance made up of only one type of atom. There are over 100 different elements. Everything on earth is made from these elements. All the known elements are listed in a table called the periodic table.

All elements are given symbols to identify them.

We must know the name and symbol for the first twenty elements in the periodic table.

All the symbols have either one or two letters in them.The first letter is a capital letter. The second letter is always a small letter.

Element Symbol

Hydrogen H

Nitrogen N

Sulfur S

One letter symbols

Two letter symbolsElement Symbol

Zinc Zn

Silver Ag

Gold Au

Compounds:Compounds consist of two or more elements chemically combined

Very often two or more elements from the periodictable join together and from new substances. These new substances are called compounds.

Water is a compound made up of two elements: hydrogen and oxygen

Water molecule

Table salt has the chemical formula NaCl.It is made up of two elements Na and Cl.

Chemical structure of sodium chloride

Carbon dioxide Co2 is a compound made up of carbonand oxygen.

Mixtures:Mixtures are made up of two or more substances mingled together but not chemically combined. Therefore mixtures can be made up of elements or compounds but in no definite amounts.

Air is a mixture of gases in no definite amounts.Sea water is a mixture of water and salt.Dolly mix is a mixture of different colored and shaped sweets.

Compounds Mixtures

Made up of a single substance Made up of two or more substances

Elements in a compound are always in a fixed ratio

Amounts of substances in a mixture can vary

Properties of a compound are different to those of the elements it contains

Properties of a mixture are similar to those of the substances in the mixture

Difficult to separate the elements of a compound

Usually easy to separate the substances in a mixture

There is usually a heat change when a compound is formed

Very little heat change when a mixture is made.

Differences between compounds and mixtures

To compare a mixture of iron and sulfur to the compound iron sulfide (FeS)

Equipment: Mass balance ,Spatula, Magnet, Test tube ,Tongs, Bunsen burner, Pestel and mortar

Chemicals: Iron filings, Sulfur

Method• 1- using a pestel and mortor, grind up a mixture containing 6g of iron and

4g of sulfur.• 2- wrap a magnet in paper and bring the magnet close to the mixture• 3- remix the iron and sulfur,using a spatula, and place the mixture in a test

tube.• 4-Heat the test tube until the mixture glows red ( do this in a fume

cupboard)• 5-continue heating gently until the mixture stops glowing• 6-Allow the test tube to cool and examine its contents. Remove the grey

solid formed from the test tube• 7- Bring a magnet close to the grey solid

What do you notice?

Result:A new substance has been formed. It is called Iron Sulfide. It cannot be separated with the use of a magnet.

Conclusion:When elements chemically combine to form compounds they loose their individual properties.

Iron Sulfur HeatIron

Sulfide

Properties of compounds:Compounds are made of different elements chemically combines. The properties of compounds are very often completely different from those of the elements from which they are made.

compounds elements

Sodium chloride (table salt)

Sodium: very reactive metal, stored under oilChlorine: poisonous green gas

Carbon dioxide (used in fire extinguishers)

Carbon: black solidOxygen: needed for substances to burn

Water (H2O) Hydrogen: Explosive gasOxygen: needed to burn substances