Year 8 ChemistryYear 8 Chemistry

Table of ContentsTable of Contents

Atoms, Elements and the Periodic TableAtoms, Elements and the Periodic TableMetals, Non-metals and MetalloidsMetals, Non-metals and MetalloidsCompoundsCompoundsChemical ReactionsChemical ReactionsReaction RatesReaction RatesAcids and BasesAcids and BasespH ScalepH Scale IndicatorsIndicators

Atoms and ElementsAtoms and Elements

All matter is made up of All matter is made up of atoms.atoms.

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

Each element has a letter Each element has a letter symbol – usually derived symbol – usually derived from its English name from its English name (first letter in capitals) or (first letter in capitals) or its original language its original language name.name.

Periodic TablePeriodic Table The original Periodic Table was constructed by Dmitri The original Periodic Table was constructed by Dmitri

Ivanivich Mendeelev, using data collected by many Ivanivich Mendeelev, using data collected by many experimental scientists (Physicists and Chemists).experimental scientists (Physicists and Chemists).

It organises the elements into groups based on their It organises the elements into groups based on their properties – in columns and rows.properties – in columns and rows.

Sub-atomic StructureSub-atomic Structure Each atom is made of three Each atom is made of three

types of particles – electrons, types of particles – electrons, protons and neutrons.protons and neutrons.

The atomic number of an The atomic number of an element tells us how many element tells us how many protons an atom has.protons an atom has.

The mass number of an The mass number of an element tells us how many element tells us how many protons plus neutrons an atom protons plus neutrons an atom has.has.

Each atom has an equal Each atom has an equal number of negative (electrons) number of negative (electrons) and positive (protons) charges and positive (protons) charges – which means the atom has – which means the atom has an overall neutral charge.an overall neutral charge.

chargecharge positionposition massmass

ElectronsElectrons NegativeNegative Shells of Shells of energyenergy

NilNil

ProtonsProtons PositivePositive NucleusNucleus 1 amu1 amu

NeutronsNeutrons NeutralNeutral NucleusNucleus 1 amu1 amu

Metals, Non-metals & MetalloidsMetals, Non-metals & Metalloids

The three main The three main groups of elements groups of elements are:are:

Metals – they are Metals – they are usually solid at room usually solid at room temperature, often temperature, often shiny, can be shaped shiny, can be shaped (malleable), drawn (malleable), drawn into wires (ductile) into wires (ductile) and usually conduct and usually conduct heat and electricity.heat and electricity.

Metals, Non-metals & MetalloidsMetals, Non-metals & Metalloids

Non-metals – they are Non-metals – they are usually gases at room usually gases at room temperature, they are temperature, they are semi-conductors of semi-conductors of electricity or heat, are electricity or heat, are brittle and therefore brittle and therefore can’t be drawn into can’t be drawn into wires or shapedwires or shaped

Metals, Non-metals & MetalloidsMetals, Non-metals & Metalloids

Metalloids – these are a Metalloids – these are a small group of nine small group of nine elements that have a elements that have a mixture of characteristics mixture of characteristics from both the metal and from both the metal and non-metal groups, non-metal groups, including Astatine – an including Astatine – an element so rare that there element so rare that there is less than a third of a is less than a third of a gram in the earth’s gram in the earth’s surface.surface.

CompoundsCompounds Compounds are formed when elements join together as Compounds are formed when elements join together as

the result of chemical reactions.the result of chemical reactions. They have a set formula and different properties to the They have a set formula and different properties to the

elements that make them. For example; Hydrogen and elements that make them. For example; Hydrogen and Oxygen gases combine to form water (2HOxygen gases combine to form water (2H22 + O + O22 2H 2H22O)O)

Chemical ReactionsChemical Reactions

Substances that react Substances that react together are called together are called reactants.reactants.

The substances they The substances they produce are called produce are called products.products.

Not all elements are Not all elements are able to react with able to react with other elements.other elements.

Chemical ReactionsChemical Reactions

Physical Changes – Physical Changes – no new substance is no new substance is produced, but some produced, but some of the properties may of the properties may change.change.

Chemical Changes – Chemical Changes – occur following a occur following a chemical reaction and chemical reaction and the properties of the the properties of the products do change.products do change.

Chemical ReactionsChemical Reactions How do we know a How do we know a

reaction has reaction has occurred?occurred? Production of GasProduction of Gas Production of Light or Production of Light or

HeatHeat Change of MassChange of Mass Permanent Change in Permanent Change in

colourcolour Formation of a Formation of a

precipitate.precipitate.

Law of Constant MassLaw of Constant Mass

Antoine Laurent Lavoisier Antoine Laurent Lavoisier developed the law of developed the law of constant mass in the constant mass in the 1750’s – not long before 1750’s – not long before losing his head to the losing his head to the guillotineguillotine

““Matter is neither created Matter is neither created nor destroyed, rather it is nor destroyed, rather it is simply transferred or simply transferred or transformed.”transformed.”

Reaction RateReaction Rate

The speed a reaction takes place at is effected by:The speed a reaction takes place at is effected by: TemperatureTemperature Concentration of reactantsConcentration of reactants Size of particles of reactantsSize of particles of reactants Use of a catalystUse of a catalyst

Acids and BasesAcids and Bases Acids are a group of Acids are a group of

chemicals with similar chemicals with similar properties, one is that properties, one is that they are sour to taste.they are sour to taste.

Acids occur naturally and Acids occur naturally and are found in foods and are found in foods and our digestive systems.our digestive systems.

However, they can cause However, they can cause problems in the problems in the environment when in too environment when in too great a concentration or great a concentration or in the wrong place.in the wrong place.

Acids and BasesAcids and Bases Bases – are a group of Bases – are a group of

chemical compounds chemical compounds that can be thought of that can be thought of as the opposite to as the opposite to acids. They have a acids. They have a bitter taste and soapy bitter taste and soapy feel.feel.

They too are found in They too are found in nature, but cause nature, but cause problems when too problems when too concentrated or in the concentrated or in the wrong place.wrong place.

Acids and BasesAcids and Bases

Neutralisation – when acids and bases Neutralisation – when acids and bases combine in a chemical reaction they cancel combine in a chemical reaction they cancel each other out and form a salt and water.each other out and form a salt and water.

Acid + Base Acid + Base Salt + Water Salt + Water

pH ScalepH Scale

The degree of acidity or ‘basisity’ are measured The degree of acidity or ‘basisity’ are measured on the pH scale.on the pH scale.

Acids are found between 1 and 7 and Bases Acids are found between 1 and 7 and Bases between 7 and 14 on the pH scale with 7 being between 7 and 14 on the pH scale with 7 being seen as neutralseen as neutral

IndicatorsIndicators

We use a range of We use a range of indicators to measure indicators to measure pHpH Litmus PaperLitmus Paper Universal IndicatorUniversal Indicator pH probespH probes