Model of an Atom

Atom contains sub-atomic particles. Protons are positively charged. Electrons are negatively charged. Neutrons have no charge. Protons and neutrons are found together in the nucleus

at the centre of the atom. Electrons freely move around the outside of the nucleus in electron shells. If there are equal numbers of protons and electrons the atom becomes and

ion.

Questions:

1) State which part of the atom is positively charged. (1 mark)

2) Describe the structure of an atom. (5 marks)

3) Draw a labelled diagram of a carbon atom. (5 marks)

Stretch question: Which sub-atomic particle can move between atoms and what happens if it moves? (2 marks)

Atoms, Elements and Compounds.

An atom is the smallest part of something. There are atoms in everything. Different atoms contain different amounts of protons, neutrons and

electrons. Atoms of the same type together is called an element. Different elements chemically joined together form a compound. Different elements not chemically joined together form a mixture.

Questions:

1) State whether oxygen is an element or a compound. (1 mark)

2) Explain the difference between an atom, an element and a compound. (3 marks)

3) Draw particle diagrams to show how Iron and Sulphur react together to form a compound. (3 marks)

Stretch question: Write a word and symbol equation to show the reaction between Iron and Sulphur. (2 marks)

Periodic Table

The periodic table lists all the elements (page 142 in year 8 planner.) The elements are specially arranged so that every column contains

elements with very similar properties. These columns of elements are called groups.

The horizontal rows are called periods. There is always a gradual change or “trend” in properties across a period.

Elements are listed in order of atomic number- this is just the number of protons in the nucleus of the atom.

Group 1 contains the alkali metals. These metals are highly reactive when mixed with water.

Group 7 contains the halogens.

Questions:

1) Which side of the table are the non-metal elements found in the periodic table? (1 mark)

2) What group and period is Gold found in? (1 mark)

3) What do we call the elements in group 1? (1 mark)

Stretch question: What can we tell about an element from its position in the periodic table? Give an example. (1 mark)

Metals and Non-metals

Metals conduct electricity and heat- energy passes through metals well making them conductors.

Metals are strong, tough and shiny if polished- they can reflect light. Metals have high melting and boiling points- a lot of heat is needed to

melt metals.

Metals have high density-a lot of particles together in a small volume. Some metals are magnetic. Non-metals are poor conductors of electricity and heat- energy does not

travel well through non-metals making them insulators. Non-metals are not strong or hard-wearing. Non-metals are dull- don’t reflect light. Non-metals are brittle-can shatter easily.

Questions:

1) State a property unique to a metal and a property unique to a non-metal.

2) Why is it sometimes useful that non-metals don’t conduct electricity? What do we use them for?

3) How can you accurately test a sample of a substance to see whether it is a metal or a non-metal?

Stretch question: How do the properties of metals link to their common functions?

Chemical/physical change.

A physical change is reversible, a chemical change is not. The freezing of water would be a physical change because it can be

reversed. A physical change is a change in which no new substance is formed. The burning of wood is a chemical change - you can't 'unburn' it. A chemical change results in the formation of one or more new

substances.

Questions:

1) Make a list of examples of physical changes and a list of chemical changes.

2) Describe one physical change and explain why it is a physical change.

3) Describe one chemical change and explain why it is a chemical change.

Stretch question: Explain what happens to atoms during a chemical change? Draw a diagram to help your explanation.

Equations

In a chemical reaction no mass is lost when the reactants (substances being reacted together) turn into the products (substances produced.)

A salt is a compound that is formed as a result of neutralisation. A base is similar to an alkali except it cannot dissolve in water. Metal + oxygen Metal oxide e.g. Zinc + oxygen Zinc oxide Symbol equation: 2Zn + O2 2ZnO Metal + water Metal hydroxide + hydrogen e.g. Sodium + water Sodium hydroxide + hydrogen Symbol equation: 2Na + 2H2O 2NaOH + H2

Metal + acid Salt + hydrogen e.g. Zinc + sulphuric acid Zinc sulphate + hydrogen Symbol equation: Zn + H2SO4 ZnSO4 + H2

Metal Carbonate + Acid Salt + Water + Carbon Dioxide e.g. Calcium Carbonate + Nitric Acid Calcium Nitrate + Water + Carbon

Dioxide Acid + Base Salt + Water e.g. Copper oxide + sulphuric acid Copper sulphate + water

Questions:

1) What is products are formed when you add a metal carbonate and an acid?

2) Magnesium oxide + nitric acid ?

3) Potassium carbonate + hydrochloric acid ?

Stretch question: Lithium carbonate + ? Lithium sulphate +?

Acids and Alkalis

Acids have a low pH. Acids can be corrosive. Acids are neutralised by bases.

Acids make hydrogen. Acids make carbon dioxide. Alkalis have a high pH. Alkalis can be corrosive. Alkalis neutralise acids to make salts. Alkalis are similar to bases except they can dissolve in water.

Questions:

1) Name household items that are acidic?

2) Name household items that are alkali?

3) What numbers and colour represent acids, alkalis and neutral on the pH scale?

Stretch question: What tests can we perform to understand whether a substance is acid or alkali?

Burning fuels

Combustion is burning fuel – a fuel reacting with oxygen to release useful energy.

Three things you need for combustion: fuel, heat and oxygen.

Questions:

1) What would happen if you took the oxygen away from a fire?

2) How can you take oxygen from a fire?

3) Make a list of different types of fuel.

Stretch question: Why is ‘stop, drop and roll’ an effective technique for putting out a clothing fire?

Collision Theory

Different reactions can happen at different rates. Reactions that occur slowly have a low rate of reaction. Reactions that happen quickly have a high rate of reaction. Burning and explosions are very fast reactions: they have a high rate of

reaction. For a chemical reaction to occur, the reactant particles must collide. But

collisions with too little energy do not produce a reaction. The particles must have enough energy for the collision to be successful

in producing a reaction. There are two ways to find the rate of a reaction:

Measure the rate at which a reactant is used up. Measure the rate at which a product is formed. Four things alter the rate of reaction: Catalysts Surface area Concentration Temperature

Questions:

1) Explain what is meant by the term rate of reaction and how can we measure it?

2) Name examples of catalysts.

3) Use collision theory to explain how catalysts, surface area, concentration and temperature effect the rate of reaction.

Stretch question: Name examples of catalysts and explain by what is meant when we say that catalysts are specific?

Reactivity series

You need to know which elements are most reactive and which are least reactive.

The reactivity shows how well a metal reacts

The reactivity series lists metals in order of their reactivity towards other substances.

A metals reactivity will show how it will behave in reactions.

More reactive substances will displace less reactive metals in a displacement reaction.

E.g. Iron + copper sulphate Iron sulphate + copper

Questions:

1. Zinc oxide + calcium 2. Magnesium + iron oxide 3. Zinc + tin oxide 4. Magnesium sulphate + Zinc 5. Calcium + copper oxide 6. Magnesium + iron sulphate

7. Tin oxide + Copper 8. Gold + copper oxide

Stretch question: Explain how the reactivity series and displacement reactions are linked?

Extraction of Metals

More reactive metals are harder to extract from their ores. Ores are naturally occurring solid materials from which a metal or

valuable mineral can be extracted so it can be sold.

Questions:

1) What is an ore?2) Can you name different example of metal ores?3) State what metals don’t you need a process of extraction for and explain why?

Stretch question: Why is it uneconomical to extract metals from ores with a low metal atom density?

Types of Rock

There are three different types of rock: Igneous Magma- molten (melted) rock is pushed up to the surface of the crust,

sometimes out through volcanoes. Once there, it cools and becomes solid. Igneous rocks contain crystals from where the liquid rock cooled. Examples: Granite, Basalt Sedimentary Sedimentary rocks are formed from layers of sediment (rock fragments or

dead matter) laid down in lakes or seas over millions of years. The high pressure caused by the rock being squashed between the layers

above and below squeezes out the water. The layers are cemented together by other materials.

Fossils can be in the sediment, these are the dead remains of animals or plants.

Examples: Limestone, chalk, sandstone. Metamorphic These are the result of heat and pressure put on existing rocks over long

periods of time. They contain small crystals and can have some layers. Examples: Marble, slate.

Questions:

1) Name the three types of rock.2) Which type of rock contains fossils?3) Which type of rock is made as a result of the addition of heat and pressure?

Stretch question: Why are fossils useful to scientists? Explain where are they found and how?

The Rock Cycle

The rock cycle takes millions of years to complete. The rock cycle involves changing the three types of rock from one to

another. This happens by: Weathering-breaking down rocks Erosion- wearing down and moving rock Transportation- moving eroded bits of rocks around the world. Deposition- laying down of sediment. Burial/compression- Squeezing and compressing layers of sediment. Heat/pressure- squashing and heating. Melting-Intense heat making rock melt. Cooling-Solidification of melted rock Exposure- Being in a position to be eroded.

Questions:

1) Draw and label a diagram to show the process known as ‘The Rock Cycle’.2) What is meant by the term erosion?3) What are the three types of weathering?

Stretch Question: Explain what factors increase rock erosion?

The Early Atmosphere

The earth was a molten ball of rock and minerals The earth’s surface was covered in volcanoes releasing carbon dioxide,

water vapour and nitrogen. The water vapour condensed as the earth cooled and rain fell. This formed

the first oceans. Comets also brought water adding to what we had. Earths early atmosphere consists of carbon, dioxide, with some water

vapour, nitrogen and traces of methane and ammonia. Bacteria first appeared Algae and other life forms evolved. They could make their own food using

the suns energy and oxygen was their waste. Oxygen levels rose steadily as algae and bacteria filled the seas. Animals evolved using oxygen to respire.

Questions:

1) What do we mean by the term ‘atmosphere’?

2) Describe how the atmosphere has changed from the early atmosphere to what atmosphere we have today.

3) What is meant by the term ‘respiration’?

Stretch Question: Explain why the evolution of plants and animals had such a big impact on the atmosphere.

Global warming

The main ideas surround global warming are that large amounts of carbon dioxide gas are being released into the atmosphere from burning of fossil fuels, forests, engine exhausts, factories etc., throughout the world.

Scientists believe that greenhouse gases like carbon dioxide cause the temperature to rise as they trap heat close to the Earth.

This is effecting our environment causing weather patterns (violent storms, flooding & droughts) to change and melting ice caps at the poles causing sea levels to rise.

Subsequently this has caused flooding in many areas of the world (especially in many coastal areas).

Most of the greenhouse gases are produced in the developed industrial countries for example the USA and in the European continent.

These countries should be more active in reducing its greenhouse emissions by researching alternative fuels and making strict rules about how much carbon they release.

They should perhaps also help and encourage developing countries like India and Brazil to reduce their emissions and prevent forests from being cut down.

Some countries are reluctant to reduce emissions due to short-term economic gains (making money).

On the whole, human activity is responsible for global warming.

Questions:

1) State how carbon dioxide is released into the atmosphere through human activity.

2) Explain what is meant by ‘the greenhouse effect’?

3) Describe and explain the effects of global warming.

Stretch question: Explain who you think is to blame for global warming and explain why.

The Earths Structure

The Earth has a layered structure made up of the core, mantle and crust. The lithosphere - the crust and upper part of the mantle - is broken into

large pieces called tectonic plates. These move slowly over the mantle. Volcanoes occur when molten rock pushes up through weaknesses in the

crust.

The molten rock cools and solidifies to form igneous rocks, such as basalt, gabbro, rhyolite and granite.

The Earth is almost a sphere. These are its main layers, starting with the outermost:

Crust - relatively thin and rocky. Mantle - has the properties of a solid, but can flow very slowly Outer core - made from liquid nickel and iron Inner core - made from solid nickel and iron The lithosphere consists of the crust and outer part of the mantle. It is the

relatively cold outer part of the Earth’s structure.

Questions:

1) Draw and label a diagram of the structure of the earth?

2) Explain how volcanoes appear.

3) Explain what tectonic plates are?

Stretch question: What is an earthquake and why do they happen? Where are you more likely to experience an earthquake?