© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 36 What is an element? All substances are made of very tiny particles called atoms. The elements

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20051 of 36

What is an element?

All substances are made of very tiny particles called atoms.

The elements are the simplest substances in the universe.

The elements are the building blocks of all other substances.

copper

carbon

There are about one hundred substances that are made up of just one type of atom. These are the elements.

helium


An element is a substance made up of only one type of atom.

Atoms in elements

Copper is an element made up of copper atoms only.

Carbon is an element made up ofcarbon atoms only.

Helium is an element made up ofhelium atoms only.


Atoms and molecules of elements

In some elements, the atoms are joined in groups of two or more. A particle containing atoms grouped in this way is called a molecule.

An element is a substance made up of only one type of atom.

Other elements, that contain atoms joined in molecules are hydrogen, nitrogen, chlorine and bromine.

Oxygen is an element made up of oxygen atoms only.

How many atoms are there in an

oxygen molecule?


The symbol for many of the more common elements uses just the first letter of the name.

Introducing chemical symbols

A standard set of symbols is used to represent elements:

hydrogen

H =carbonC =fluorineF =

oxygenO =nitrogen

N =

Others elements have the first two letters.

lithiumLi =aluminium

Al =heliumHe

=

Some of the symbols are not always as you might expect.

leadPb =goldAu =silver

Ag =

iodineI =


Symbols as an international language


How to write symbols for elements

Two important rules should be followed when writing the symbols of elements so that there is no confusion.

1. The first letter of an element’s symbol is always a capital letter.

2. If there are two letters in the element’s symbol, the second letter is always a small letter.

e.g. N (not n) for

nitrogen

e.g. Co (not CO) for cobalt

No, Watson! It was carbon monoxide

poisoning – not cobalt.


Chemical symbols game


The Story of ‘The Kid’


1. Board game: carbon, helium, two sulphurs

2. Relative: sulphur, oxygen, nitrogen 3. Fuel: carbon, oxygen, aluminium

4. Group of fish: sulphur, hydrogen, oxygen, aluminium

5. For the rubbish: boron, iodine, nitrogen

CHeSS

SON

COAl

SHOAl

BIN

Spelling with symbols activity

Write down the symbols for each element listed and use these to spell out a word that matches the clue.


In some elements, the atoms are joined together and form molecules. Combining the symbols of the atoms in a molecule gives you the formula of the molecule.

What is the formula for the molecules in each element?

Symbols for molecules of elements

nitrogen

oxygen

N2

O2There are groups of

two atoms in each

molecule.


Arranging elements


Metals and non-metals in the periodic table

The periodic table is a list of all the known elements which are arranged according to the similarities in their properties.

Non-metals are mostly on the right.

Metals are on the left and in the centre.

What type of elements are between metals and non-metals?

Xe


Types of elements in the periodic table


What is a compound?

A compound is the substance produced when two or more elements combine in a chemical reaction.

A compound is always made up of two or moredifferent types of atom.

Two elements, hydrogen (H) and oxygen (O), combine to make the compound, water.

Which two elements combine to make the compound carbon dioxide?


Making a compound – carbon dioxide

A compound has very different properties to the elements from which it is made.

carbon dioxide

A colourless gas which is used to put out fires.

to make

carbon

A black solid which can be

used as a fuel.

combines with

compound

elementsoxygen

A colourless gas which is essential

for life.


Making a compound – water

What are the elements which make up water? In what ways are the elements different to their compound?

to makecombines with

compound

elementswater

A liquid which is essential to our

lives and has many different uses.

hydrogen

A colourless gas which is used in hot air balloons.

A colourless gas which is essential

for life.

oxygen


Element or compound?




Chemical reaction to make water

Elements combine with each other to make new substances called compounds.

In a chemical reaction new substances are formed.

hydrogen

The substances which combine in a reaction are the reactants. The new substances produced in a reaction are the products.

Compounds can also combine with elements or other

The products have different properties to the reactants fromwhich they are formed.

water

compounds to make new compounds.

+oxygen


When the two elements, hydrogen and oxygen, combine in a chemical reaction,

Atoms joining in a chemical reaction

In a chemical reaction, the atoms in the reactants become joined in different ways and this is how

new substances are formed.

hydrogen oxygen water+

+H H

H HO O

the hydrogen and oxygen atoms do not just mix together they become joined to one another.


Glossary

atom – The smallest particle that can exist on its own.

compound – Substance made up of two or more different elements that are chemically joined together.

element – Substance made up of only one type of atom.

formula – The symbols and numbers that represent the atoms in a substance.

molecule – Two or more atoms that are chemically joined together.

periodic table – Table in which all known elements are arranged based on their properties.

symbol – One or two letters that represent an element.


Properties of elements and compounds

Why is it safe to put sodium chloride on fish and chips… …but not safe to use sodium and chlorine?


Compounds contain two or more different types of atom.

Elements are materials made up of one type of atom only.

Atoms in elements and compounds

The element, hydrogen, exists as molecules.

Each hydrogen molecule is made up of two hydrogen atoms joined together.

The compound, water, exists as molecules.

Each water molecule consists of two hydrogen atoms joined to one oxygen atom.

H H




A compound is made when atoms of different elements react and join together.

For example, water is produced from the chemical reaction between hydrogen and oxygen.

Making a compound – water

Two hydrogen molecules react with one oxygen molecule to produce two molecules of water.

+H H

H HO O

hydrogen oxygen water+

Why does water have different properties to its elements?


A compound is not a mixture

The atoms in water, the compound made when hydrogen and oxygen react and their atoms become chemically joined to each other, look like this…

The atoms in a mixture of hydrogen gas and oxygen gas, which have not reacted with each other, look like this…


To name simple compounds of metals and non-metals:

Naming simple compounds

2. Write down the name of the non-metal, changing the ending of the word to “-ide”.

1. Write down the name of the metal.

What is the name of the compound made when the following elements combine?

magnesium and oxygen

sodium and chlorine

oxygen and iron

magnesium oxide

sodium chloride

iron oxide


What is the name of each compound formed by these metal and non-metal elements?

nitrogenlithium

sulphurzinc

iodinenickel

brominealuminium

oxygentin

chlorinesodium

nitrogenmagnesium

sulphuriron

Name of compoundElement 2Element 1

iron sulphide

magnesium nitride

sodium chloride

tin oxide

aluminium bromide

nickel iodide

zinc sulphide

lithium nitride

Naming simple compounds


Many compounds contain more than two elements.

oxygenbrominealuminium

oxygensulphurcopper

oxygen

oxygen

oxygen

Element 3

nitrogensodium

magnesium nitratenitrogenmagnesium

nickel sulphatesulphurnickel

Name of compoundElement 2Element 1

sodium nitrate

copper sulphate

aluminium bromate

Naming further compounds

For compounds containing two elements plus oxygen, the ending of the other non-metal usually changes to “--ate”.


A compound always contains a particular amount of each element. It has a fixed composition.

Composition of compounds

A compound contains atoms from different elements that are chemically joined together.

Compound names can get quite long and complicated, so the symbols of the elements are used as a shorthand.

The symbols of the elements in a compound are combined to give the formula of the compound.

What is the formula of carbon dioxide?


carbon dioxide

A formula uses the symbols of the elements in a compound.

When there is more than one atom of each element, the number is always written after the symbol.

Writing a formula

carbon atom = 1formula =

hydrogen atoms = 2formula =

The formula shows the ratio of atoms in a compound.

water

CO2

H2O

oxygen atoms = 2

oxygen atom = 1


1. Titanium oxideFor every titanium atom there are two oxygen atoms.Formula =

2. Lithium oxide For every two lithium atoms there is one oxygen atom.

Formula =

3. Aluminium chloride For every aluminium atom there are three chlorine atoms.

Formula =

What is the formula of each of these compounds?

What is the formula?

TiO2

Li2O

AlCl3

(In a formula put the metal first as when naming a compound.)


1. Silicon chlorideFor every silicon atom there are four chlorine atoms.Formula =

2. Manganese oxide For every manganese atom there are two oxygen atoms.

Formula =

3. Aluminium oxide For every two aluminium atoms there are three oxygen atoms.

Formula =

What is the formula of each of these compounds?

What is the formula?

SiCl4

MnO2

Al2O3

(In a formula put the metal first as when naming a compound.)


What is the ratio of atoms?


What does a formula show?


Writing a word equation

A word equation can be used to describe any chemical reaction, i.e. any process in which atoms become joined in different ways.

The steps for writing a word equation are:

1. On the right-handside, put the name of the reactant(s).If there are two or more reactants, link them with a + + sign.

2. In the middle, write down an arrow ().

3. On the right-handside, put the name of the product(s). If there are two or more products, link them with a + + sign.


The lead and oxygen don’t mix, they react to form lead oxide. This means that the lead and oxygen atoms in the product are joined differently to the atoms in the reactants .

Lead reacts with oxygen to form lead oxide.

lead + oxygen lead oxide

Why is lead oxide so different to both lead and oxygen?

What is the word equation?

What is the word equation for this reaction?


1. Limestone (calcium carbonate) is heated to make calcium oxide and carbon dioxide.

2. Magnesium reacts with hydrochloric acid to make magnesium chloride and hydrogen.

3. Methane is burnt to make carbon dioxide and water.

calcium carbonate calcium oxide +carbon dioxide

magnesium + hydrochloric acid magnesium chloride + hydrogen

methane + oxygen carbon dioxide + water

What is the word equation?

Write out word equations for the following chemical reactions.


A mixture is not the same as a compound:

1. The proportions of the substances in a mixture are not fixed.

2. The properties of a mixture are often an “average” of the properties of its ingredients (e.g. a mixture of a black and

white powder is grey).

3. The substances in a mixture are just mixed, not chemically joined, and so it is usually quite easy to separate the

A mixture contains two or more substances that are mixedmixed together but have not reacted with each other.

Sea water is a mixture of salts, water and other substances.

What is a mixture?

ingredients (e.g. it is easy to get salt from sea water).


Element, compound or mixture?


Element, compound or mixture?


Liquids that do not mix are described as immiscible.

Examples of immiscible liquids are water with oil and water with petrol.

On a small scale, immiscible liquids can be separated by simply removing the top layer using a pipette.

oil

water water oil

Separating immiscible liquids


Liquids that do mix are described as miscible.

Examples of miscible liquids are water with alcohol and petrol with kerosine.

Miscible liquids can be separated by heating them to boiling. The components of the mixture have different boiling points and so will boil off at different temperatures.

A condenser is used to recover the liquids as they boil off. This piece of apparatus is a tube that has cold water circulating around the outside. It cools down vapours and condenses them back to a liquid.

Substances with low boiling points are collected first, while those with higher boiling points are collected later.

Separating miscible liquids


Distillation apparatus


How can each mixture be separated?

alcoholalcohol and water

cooking oilcooking oil and water

watersea water

saltsea water

glassglass and water

MethodWantedMixture

filter

evaporate

distil

pipette

distil

Separating mixtures


Reggie has been given a mixture of salt, sand and water.

He needs to separate these three substances but cannot remember how, so Reggie needs your help!

Experiment to separate a mixture

Write an experimental plan for Reggie to follow so that he will end up with the sand, salt and water in separate containers.

Start your plan with a list of the equipment that is needed for separating this mixture. Then write a step by step plan that is easy for Reggie or anyone else to follow.


Glossary

atom – The smallest particle that can exist on its own.

boiling point – Temperature at which a pure liquid becomes a gas.

compound – Substance made up of two or more different types of atoms that are chemically joined together.

element – Substance made up of only one type of atom.

formula – The symbols and numbers that represent the ratio of different atoms in a substance.

immiscible – Liquids which do not mix.

miscible – Liquids which do mix.

mixture – Two or more substances that are mixed but not chemically joined together.


True or false?

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© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 36 What is an element? All substances are made of very tiny particles called atoms. The elements