some new symbols to get used to…

1 of 20 GCSE Core Chemistry

Exam tip; A symbol represents 1 atom of an element

Some new symbols to get used to…



Key words; Atom, Compound, Electron, Element, Symbol



How do you know?

H H



Learning Objectives

By the end of the lesson I can:

•Describe how elements contain only one type of atom

•Understand that symbols are used for atoms to show what happens in chemical reactions.

•Know that all 100 known elements are listed on the periodic table and groups have similar properties



Atoms and symbols

All substances are made up of p______. The smallest p_____ that can take part in a chemical reaction is called an a___.

Elements are substances that each contain only _______ of atom. The atoms of each element are represented by a symbol.

Examples of symbols used for elements are O (used for ______), N (used for _______) and Cu (used for ______).

articlesarticle

tom

one type

oxygen nitrogen

copper



More work on symbols

Fill in the gaps in the table below.

Sodium

Bromine

Ag

C

Chlorine

SymbolName of element

Cl

Carbon

Silver

Br

Na



How are the elements arranged?

Answer: Using the Periodic Table

Vertical columns are called

___________ and

horizontal rows are called

___________.

groups

periods



Elements, mixtures and compounds

Elements – these are substances containing only ______________. For example, sodium is an element and is made up of sodium atoms only.

Compounds – these are substances made up of two or more types of atom. These atoms are joined together chemically. For example, carbon dioxide contains carbon and oxygen atoms joined together by chemical bonds.

one type of atom



Mixtures – these are not pure substances. The compounds and/or elements making them up are not joined chemically. For example, air is a mixture of gases like oxygen (an element) and carbon dioxide (a compound).



Elements, mixtures and compounds, continued

Classify the following substances as elements, mixtures or compounds.

mixture compound element



Learning Objectives


•Describe how elements contain only one type of atom


•Know that all 100 known elements are listed on the periodic table and groups have similar properties



Key words; Atom, Compound, Electron, Element, Symbol



Learning Objectives



•Know that atoms bond and rearrange in a chemical reaction



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.

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 has different properties to the elements from A compound has different properties to the elements from which it is made because the atoms are joined differently.which it is made because the atoms are joined differently.

Black solid used as fuel.

Colourless gas in which many

substances burn.

Colourless gas used in fizzy drinks and fire extinguishers.

+

+ O OC

carbon oxygen carbon dioxide+



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:

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



How do we name compounds?

The rules are:

1. If there are two elements present, then the name ends in –IDE.

For example, the formula CuS represents the compound _________ide.

2. If there are three elements present and the third one is oxygen, then the name ends in –ATE.

For example, the formula CuSO4 represents _________ate.

copper sulf

copper sulf



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



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

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



Naming compounds, continued

Name the compounds in the table below.

Formula Name

AlCl3CuO

Fe2O3

CaSO4

CaCO3

MgBr2

NaNO3

Aluminium chloride

Copper oxide

Iron oxide

Calcium sulfate

Calcium carbonate

Magnesium bromide

Sodium nitrate



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.

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?

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?

SiCl4

MnO2

Al2O3

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



Learning Objectives






Learning Objectives




•Work safely in the lab to make compounds from elements



Chemical reactions

The substances that react are called the

REACTANTS.The substances formed are called the

PRODUCTS.

To represent chemical reactions we write word equations or symbol equations.

REACTANTS PRODUCTS



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 for this reaction?



Chemical reactions, continued

Write word equations for the following reactions

1 When sodium is burned in oxygen, sodium oxide is formed.

sodium(s) + oxygen(g) sodium oxide(s)

2 When solid calcium carbonate is heated, it decomposes into solid calcium oxide and carbon dioxide gas.

Calcium carbonate(s)calcium oxide(s)

heat carbon dioxide(g)+



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

Write out word equations for the following chemical reactions.



Investigation: For each of the following;

• Burn magnesium

• Pour hydrochloric acid over magnesium

• Pour sulphuric acid over zinc

1. Complete the experiment & write an observationWrite a word equationWrite a symbol equationBalance the equationDescribe the ratio of atoms in the compound composition of the products



1) When calcium carbonate burns it turns…..(complete the experiment & write an observation)

calcium carbonate calcium oxide +carbon dioxide2) complete the word equation

3) CaCO3(s) CaO(s) + CO2(g) complete the symbol equation4) 1 Ca 1 Ca

1 C 1 C3 O 3 O balance the equation

5) 1 Calcium atom to every 1 oxygen atom AND 1 carbon atom to every 2 oxygen atoms. describe the ratio of atoms in the compound composition of the products

6) complete diagrams of at least one of the equations



Does the mass change during a chemical reaction?

The answer to this is ___.NO

For example, when 56 g of iron reacts with 32 g of sulfur iron sulfide is formed. The mass of the iron sulfide formed is __ g.88

When 48 g of magnesium is heated in oxygen, 80 g of magnesium oxide is formed. What mass of oxygen is needed to react with the magnesium?

The answer is __ g. 32



Burning fossil fuels

The three fossil fuels are:Coal, oil and natural gas.

When the fossil fuels are burned in enough air they always form water and carbon dioxide. Carbon dioxide is a __________ gas and is linked to g____ w______.

greenhouse lobalarming

Write the word equation for methane (natural gas) burning in oxygen.

methane(g) + oxygen(g) carbon dioxide(g) + water(l)



The Reactivity Series

Metals are arranged in order of how reactive they are. A more reactive metal will displace a less reactive one from its compounds.

For example, zinc will displace copper from copper sulfate to give zinc sulfate plus copper. The word equation is:

zinc(s) + copper sulfate(aq) zinc sulfate(aq) + copper



Learning Objectives




•Work safely in the lab to make compounds from elements

some new symbols to get used to…

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