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CHEMISTRY Mixtures

1. Name a common mixture of gases. The air 2. Name a common mixture of liquids sea water 3. Name a common mixture of solids sand and salt 4. Name a mixture of a liquid and a solid. Salt solution Separation Techniques

Method Used to separate

Apparatus used Examples

Filtering (Filtration)

Solid particles which do not dissolve from the liquid they are in

• Tea leaves from a cup of tea

• Sand from a mixture of sand and water

Evaporation Dissolved substances from a solution

• Salt from salt solution

Distillation (Evaporation followed by condensation)

The liquid from the dissolved solid in a solution or one liquid from a mixture of liquids

• Water from salt solution

• Alcohol from a mixture of alcohol and water

Chromatography

The colours can be separated from a mixture of colours

• The colours found in ink

• The food colourings found in fruit juice

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5. How could you separate a mixture of water and sand? filtration 6. How could you collect pure water from salty water? distillation 7. How could you test the purity of the water? Boils at 1000C 8. How could you collect pure salt from salty water? Evaporation 9. How could you collect a sample of ethanol (alcohol) from wine?

Fractional distillation

10. What method could you use to see if two smarties contained the same dye. Chromatography Define the following words:- a) Solute a solid which dissolves b) Solvent a liquid which dissolves a solute c) Solution what is formed when a solid dissolves in a liquid. d) Residue What is left in the filter paper after filtration e) Filtrate the clear liquid which comes through a filter paper. f) Distillate the liquid obtained by distillation g) Suspension a solid floating in a liquid but not dissolved Elements

Each element has its own chemical symbol. For example, the chemical symbol for oxygen is O. Some elements have their atoms joined to each other in small groups called molecules. Oxygen is an example.

A molecule of oxygen consists of two oxygen atoms joined together.

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1. Give examples of metallic elements. iron, magnesium, sodium, calcium, zinc, aluminium, copper, mercury (any of the grey elements on periodic table)

2. Give examples of non metallic elements. Oxygen, nitrogen, sulphur, carbon, hydrogen, (any of the yellow elements on the chart)

Metals and non-metals The properties of a substance are the words that we use to describe it, or measurements that we can make on it. Metals and non-metals have different properties.

Metals Non-metals

good conductors of heat and electricity poor conductors of heat and electricity

shiny dull

solids with a high melting point (except for mercury)

most are solids or gases

found on the left-hand side of the Periodic Table

found on the right-hand side of the Periodic Table

three metals are magnetic no non-metals are magnetic

metals can burn to form alkaline oxides non-metals can burn to form acidic oxides

flexible brittle

3. Name four physical properties of metallic elements.

Ductile,

high density,

conductors of heat and electricity,

shiny,

sonorous

malleable

4. Name four physical properties of non metallic elements.

Brittle or gas,

low density,

insulators of electricity and heat,

dull

5. Name a chemical difference between the oxides of metals and non metals.

Metal oxides are acidic,

non metallic are alkaline

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Compounds Elements can join together to make compounds. The name of the compound tells you the elements that are in it. Compounds made from two elements always have a name which ends in ‘-ide’.

These elements join together … … to make these compounds

carbon, oxygen carbon dioxide

sodium, chlorine sodium chloride

magnesium, oxygen magnesium oxide

A chemical formula tells you the name and number of atoms in a compound. The smallest particle of many compounds is called a molecule. Molecules are made up of atoms. Some elements are also made of molecules. For example, a molecule of oxygen contains two oxygen atoms joined together. The formula is O2.

A molecule of water.

The chemical formula tells you the numbers of atoms of each element in a compound. Each element in the chemical formula is shown by its chemical symbol. For example:

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Elements Compounds Mixtures

atoms of helium (He)

molecules of carbon dioxide (CO2)

a mixture of helium and oxygen

molecules of oxygen (O2)

molecules of water (H2O)

a mixture of carbon dioxide and oxygen

a lump of carbon (C)

a lump of sodium chloride (NaCl)

a lump of bronze (an alloy of copper and tin)

1. Water consists of 2 hydrogen atoms and one oxygen atom combined together. Describe

water clear, wet, colourless

2. Describe Hydrogen. Clear light gas, inflammable 3. Describe Oxygen. Clear gas, helps things to burn 4. Repeat Q1, 2, 3 using another example to show that when elements join to form compounds the compound has different properties from the elements.

Carbon is a black solid Oxygen is a clear gas which helps things to burn Carbon dioxide is a clear dense gas which puts fires out

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Dissolving

Some solids dissolve in water to make a solution. These solids are soluble. A solution is made from a solute (solid) and a solvent (liquid). When a solution is formed, the liquid is always clear (transparent).

Solids that do not dissolve are insoluble. When an insoluble solid is mixed with water, the water goes cloudy. Sometimes the solid will sink to the bottom of the water.

Other liquids (e.g. white spirit, ethanol) can also be used as solvents. Solutes which are insoluble in water may dissolve in other solvents.

If you keep adding solutes to a solvent, you will get to a point where no more will dissolve. A saturated solution cannot dissolve any more solute. More solid will dissolve if you add more solvent (e.g. water) or increase the temperature.

1. When a chemical dissolves in a liquid, is it a chemical or a physical change? physical 2. How do you know if a coloured solid has completely dissolved?

The particles are no longer visible in the liquid.

3. How can you speed up dissolving? 3 ways.

Stir,

heat,

grind up the particles

4. Name a solid that will dissolve in water. Salt, sugar, copper sulphate

5. Name a chemical which will dissolve in ethanol (alcohol) but not in water. Paint, permanent ink 6. Name a chemical which will dissolve in propanone (acetone) but not in water. Nail varnish 7. When tap water evaporates, what is left behind? minerals 8. When distilled water evaporated, what is left? Nothing

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9. What are the two tests to show that a chemical contains water?

Cobalt chloride paper goes from blue to pink.

Copper sulphate goes from white to blue

Solids, liquids and gases

SOLID

• Solids are made up of particles that are very

close together and are held tightly together by strong bonds.

• Solids cannot be squashed, do not flow, have a fixed shape and volume, and have a high density.

LIQUID

• Liquids are made up of particles that are fairly close together; the bonds between the particles are weaker than the bonds in solids.

• Liquids cannot be squashed, flow quite easily, and have a fixed volume but no fixed shape.

• Although they are dense, liquids usually have a lower density than solids.

GAS

• Gases are made up of particles that are well spread out, with no bonds between them.

• Gases are quite easy to squash, flow easily, have no fixed volume and no fixed shape.

• Gases have a lower density than liquids.

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SOLID

LIQUID

GAS

Diffusion The natural mixing of substances is called diffusion. Diffusion occurs because particles in a substance are always moving around. Diffusion is fastest in gases, and slower in liquids. Diffusion in solids is extremely slow. Pressure in gases Pressure is caused by particles hitting the walls of the container they are in. If the pressure becomes too great for a fixed container to hold, it will burst.

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The pressure may increase because: • the container has been squashed, making the volume smaller; this means that the

particles will be hitting the walls more often. • the number of particles has been increased, which means there are more particles

moving around to hit the walls. • the temperature of the particles has increased, so they will move around faster and

hit the walls harder and more often.

Naming chemicals

1. The clue to a chemical being an element is that its chemical name is what? A single word

2. The clue that a chemical is a compound is that its chemical name is what? Two or

more words 3. Name 5 solid elements

lead

copper

iron

sulphur

carbon etc

4. Name 5 metalic elements Sodium, Calcium, Magnesium, Copper, Iron, Zinc

5. Name 5 gaseous elements

Oxygen, nitrogen, helium, chlorine, neon

6. Name 5 compounds copper sulphate, copper oxide, copper carbonate, sodium chloride, magnesium oxide

7. Name 3 mixtures of elements iron and sulphur oxygen and nitrogen carbon and lead

8. Name 3 mixtures of compounds copper sulphate and water carbon dioxide and sulphur dioxide sodium chloride and water

9. Compounds usually contain a metalic element attached to some non metalic elements. Give an example. Copper carbonate

10. A group of compounds are called – ides. Give an example and say what makes them

an –ide 2 elements combined eg iron sulphide or magnesium oxide

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11. A group of compounds are called –ates. Give an example and say what makes them an –ate. 3 or more elements combined like copper carbonate = copper oxygen and carbon

12. What – ide will be made out of Iodine – iodide Chlorine – chloride Oxygen – Oxide

13. What –ate will be made out of Carbon and oxygen – carbonate Sulphur and oxygen - sulphate Nitrogen and oxygen - nitrate

14. What will Magnesium, sulphur and oxygen make? Magnesium sulphate

15. What will magnesium and oxygen make? Magnesium oxide Fire A fire needs three things to keep burning: fuel, oxygen and heat. We show these three things on the Fire Triangle.

If any one of these three things runs out, the fire will go out. Fire extinguishers are used for putting out fires.

Water is often used to put out fires, because it takes away the heat.

However, water should never be used on oil or petrol fires, because it makes the burning fuel spread out.

Foam, powder or carbon dioxide (CO2) extinguishers work by stopping oxygen

getting to the flames.

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Reactions

Chemical reactions In a chemical reaction a new substance is always formed. Most chemical changes are not easily reversed; they are irreversible. You can tell that a reaction has occurred if there is a

colour change

a gas is given off.

Most chemical reactions also involve an energy change. This is usually in the form of heat, but can also involve light being given off (for example, when something burns).

1. Write down the word equation for respiration. Food + Oxygen carbon dioxide + water + energy Reactants Products 2. Give an example of an exothermic reaction.

Most reactions (give off heat ie a flame or blowing up or just getting hot) 3. Give an example of an endothermic reaction.

Copper + Oxygen copper oxide

Any decomposition reaction When two chemicals react together they COMBINE to make a compound. When chemicals mix they mix to form a MIXTURE 4. Combination – write a chemical equation to show combination not involving oxygen.

Copper + sulphur Copper sulphide

any other metal doing the same or combining with iodine or chlorine

Oxidation • Oxidation reactions happen when something reacts with oxygen. Most oxidation

reactions give out heat energy. 5. Write a chemical equation to show oxidation of:-

a) a metal any metal + oxygen any metal oxide

eg. Magnesium + oxygen magnesium oxide

b) a non metal Carbon or sulphur or nitrogen + oxygen oxide

eg. sulphur + oxygen magnesium oxide

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6. Why is it not possible to get gold oxide? It is too unreactive to combine with oxygen

7. If a chemical oxidises, what will happen to its mass? It will increase

Burning When a metal burns, the metal combines with oxygen from the air to form a chemical called an oxide. We can show this using a word equation. The chemicals that you start with are called the reactants. The chemicals at the end are called the products. magnesium + oxygen

reactants -------

magnesium oxideproducts

Fossil fuels contain a lot of carbon and hydrogen. They are called Hydrocarbon fuels. Hydrocarbon fuels are made from the elements carbon and hydrogen. Coal, oil and natural gas (methane) are all hydrocarbons. When hydrocarbons burn they form carbon dioxide and water, and release heat energy

fuel + oxygen ------- carbon dioxide + water (+ energy) eg. methane + oxygen ------ carbon dioxide + water If there is not enough oxygen available, carbon monoxide or even soot is produced. 8. Write a chemical equation to show burning of an element.

Any element + oxygen element oxide

9. What is another description of this reaction. Combination or oxidation

10. What is produced when a hydrocarbon burns?

Carbon dioxide,

water vapour

sometimes carbon if there is not enough oxygen.

11. Give some examples of hydrocarbon fuels. Petrol, oil, wood, gas, paper, wax etc

Decomposition 12. Write an equation to show the decomposition of copper carbonate.

Copper carbonate copper oxide + carbon dioxide

13. Write another decomposition equation. Calcium carbonate calcium oxide + carbon dioxide Mercury oxide mercury + oxygen Red lead oxide yellow lead oxide + oxygen

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Law of conservation of mass In a chemical reaction, the mass of the reactants is always the same as the mass of the products. This is because atoms are not created or destroyed in chemical reactions; they are just rearranged into different compounds.

Acids and Bases

Indicators are coloured dyes which often come from plants such as red cabbage and beetroot. Acids make indicators change colour. Litmus is an indicator which turns red in acids. Common acids include vinegar and lemon juice. Fizzy drinks, pickles and spicy sauces also contain acids. Stronger acids such as sulphuric and nitric acids can be more dangerous. Often they are corrosive. Alkalis have a different effect on indicators to acids. Litmus turns blue in alkalis. Alkalis can also be corrosive. Weak alkalis include soap and toothpaste. Neutralising reactions can be important: • in gardening and agriculture, to make sure the soil is the correct pH • when dealing with insect stings and bites • to control indigestion caused by excess acid in the stomach • to keep foods such as jam at the correct pH.

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1. How could you make an indicator? Boil red cabbage in water or propanol

2. Name a:- strong acid, sulphuric (battery acid), hydrochloric acid weak acid, vinegar neutral, water weak base, stomach powder , bicarbonate of soda strong base oven cleaner, sodium hydroxide 3. If equal volumes of equal strengths acid and base are added, what will be the pH of the product? 7 (neutral) 4. If twice as much acid is added to half as much base of equal strengths, what will be

the pH of the product? 3 (an acid) 5. What is the equation to show salt formation in neutralisation. Acid + base salt + water 6. If you added sodium hydroxide (a strong base) to hydrochloric acid what are the

products? Write an equation. Sodium hydroxide + hydrochloric acid sodium chloride + water

7. Give an example of neutralisation on the farm. Lime on the fields to neutralise acid soil

8. Give an example of neutralisation in the bathroom. tooth paste on the acid on your teeth

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Gases

1. Air is a mixture of gases, name four of them. Oxygen, nitrogen, carbon dioxide, argon, neon, water vapour

2. List them in order of abundance.

Nitrogen – 78%

Oxygen – 21%

carbon dioxide – less than 1%

the rest Oxygen 1. What are the properties of oxygen? (3 of them)

Helps things to burn,

a gas,

clear

2. What is oxygen used for? a) In nature burning, respiration b) In industry Increasing the heat of burning, steel production 3. What is the test for oxygen? Relights a glowing splint Carbon dioxide 1. What are the properties of carbon dioxide? (3 of them)

denser than air,

puts fires out,

suffocates you

2. What is it used for?

Fire extinguishers

Freezing foods

Fizzy drinks

3. How is it made naturally in nature? Respiration, burning 4. How may a pure sample be made in the laboratory?

Heat

add acid to a carbonate

5. How is it tested? Clear Lime water goes cloudy

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Pollution

Acid rain The air contains small amounts of the following gases: • carbon dioxide, produced by combustion of fuels and respiration • sulphur dioxide, formed when sulphur burns in volcanoes • nitrogen oxides, produced during lightening storms. These gases dissolve in water to form acids, so rainwater is naturally acidic (pH between 5.6 and 5.9). Our rainwater has become even more acidic (pH between 3 and 5.5) due to air pollution from burning fossil fuels. This is what we call acid rain. The main sources of this pollution are power stations and cars. Both burn large amounts of fossil fuels and release more carbon dioxide, sulphur dioxide and nitrogen oxides. Sulphur dioxide and nitrogen oxides are the main contributors to acid rain.

Problems caused by acid rain Acid rain causes damage to our environment in several ways: • Metals and carbonate rocks (like limestone and marble) react faster with acid rain

than with normal rainwater. • Plants and water life are damaged and killed by acid rain. Global warming Carbon dioxide and other gases trap the Sun’s energy. This is sometimes called the greenhouse effect.

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The increased levels of carbon dioxide in the atmosphere are caused by burning more fossil fuels, and destroying large areas of forest.

1. Name two liquids which cause air pollution. Sulphuric and nitric acid causing acid rain

2. Name two gases which cause this pollution. Sulphur dioxide and nitrogen oxide

3. Name two elements which make these gases. Sulphur and nitrogen

4. Where do these elements come from to cause the pollution. Fossil fuels burning. Such as Coal in power stations, petrol/diesel in cars

Displacement Reactions

Metals can be arranged in a Reactivity Series. The most reactive metals are placed at the top of the table. More reactive metals can displace less reactive metals from their compounds. In a displacement reaction, the more reactive metal will form a compound, and the less reactive metal is left on its own as the pure element. • Displacement reactions happen when a metal displaces a less reactive metal from

a solution. The reaction gives out heat energy. For example, iron is more reactive than copper, so it will displace copper from a compound.

iron + copper chloride --------iron chloride + copper Zinc is more reactive than iron, so iron will not displace zinc from a compound.

iron + zinc chloride -------- no reaction

You can use displacement reactions to work out the position of a metal in the Reactivity Series. For instance, zinc will displace lead from a compound, so we know that zinc is more reactive than lead. 14. Complete the following equation.;-

Zinc + copper sulphate Zinc sulphate + copper

15. Describe what you may see. When you put a lump of Zinc into copper sulphate, Copper coats the zinc making it go redy brown.

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Smelting 16. Complete the following equation:-

Copper oxide + Carbon copper + carbon dioxide

17. Describe what you may see. The black powder (copper oxide and carbon) goes red and the gas escaping may make it look as if the powder is boiling

18. What is the name given to this method of getting metals from their ores. (S _ _ _ T _ _ G) smelting

19. Carbon is described as the reducing agent.

What is a reducing agent? A reactive substance which takes oxygen from other things. It does not

have to be an element eg carbon monoxide is a very powerful reducing agent as it wants to form carbon dioxide.

20. How would magnesium react with:- - air? Burns brightly - Water? Bubbles slightly, burns in steam - Acid? Bubbles giving off hydrogen

Metal extraction

1. Why have metals like gold been around for a long time? They are unreactive and have been found as lumps

2. Most metals are found combined with other elements as raw materials. What do we call these raw materials? Ores

3. Which do you think was used first, Copper or Bronze? Copper 4. Why? Bronze is made by mixing copper with tin (an alloy)

5. The iron age came about because they discovered iron.

What was the reducing agent which reduced the ore? Carbon

6. The bronze age came about after the discovery of which two metals? Copper and tin

7. When metals are mixed to change their properties like this, what do we call the

mixture of metals? Alloys

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Iron from a blast furnace

8. What goes into the top of a blast furnace? Iron oxide, coke, limestone

9. What is sinter? Mixture of iron oxide and coke 10. What created the heat necessary for the reaction to take place?

Hot air blowing on coke

11. Write the equation for the reaction in a blast furnace Iron oxide + carbon iron + carbon dioxide

12. At what temperature does a blast furnace work? About 16000C 13. What gas comes out of the top? Carbon dioxide

14. What is the name of the collection of impurities which float on top of the molten iron?

Slag 15. The iron produced contains too much of what element? Carbon

16. How is this element removed? Bubbling oxygen through which combines with

the carbon to form carbon dioxide. 17. Other elements are added to change the properties of the iron, what do we call the

metal alloy which results? Steel 18. What is this alloy used in? Girders etc Copper

19. What is the name of copper’s ore? Malachite/copper carbonate 20. When copper ore is heated, what gas is given off?

Carbon dioxide from the carbonate

21. What is left behind? Copper oxide 22. What is this type of reaction called? Decomposition

23. How is the oxygen removed from Q 21 ? reduce with carbon

24. Write an equation for Q23

CuO + C CO2 + Cu

25. What are copper’s properties? Bendy, good conductor of electricity and heat, sonerous etc

26. What can it be used for? Pipes, pans,

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27. Lead is produced in the same way, how does lead differ from copper? Colour,

softer, poisonous 28. What can lead be used for? Roofing, weights Aluminium

29. What is Aluminium’s ore called? Bauxite 30. It is converted into Alumina, what is the chemical name for alumina.

Aluminium oxide

31. Why can’t aluminium be removed by smelting? Aluminium is more reactive that carbon so will not let go of its oxygen

32. How is Aluminium obtained from its ore? Electrolysis 33. What are the properties of Aluminium?

Light, strong, reactive

34. What is Aluminium used for? Aeroplanes, power cables Plastic

35. What is plastic made from? Oil 36. What are the advantages of plastic over metal?

Good insulator, doesn’t rust, light

37. What are the advantages of metal over plastic? Stronger 38. Give some examples of where plastic has replaced metal or glass. Bottles, garden furniture, cars

Minerals

Complete the following paragraphs Malachite

Malachite is a green powder. When heated it decomposes to form a

black powder called Copper oxide and gives off a gas called Carbon

dioxide . If the residue is added to sulphuric acid a salt is produced called Copper

Sulphate which is a blue colour. If a nail is placed into this liquid a red coating is

found to form on the nail which is called copper.

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Limestone When acid is added to limestone Carbon dioxide is given off showing that limestone

belongs to the group of chemicals called carbonates. When placed in a flame the

limestone gives off a red coloured flame showing that the metallic part of limestone

is calcium . The full name for limestone is therefore Calcium carbonate.

If a lump of limestone is heated Carbon dioxide is given off and calcium oxide is left

behind. The common name for this compound is quick lime. If water is added to this

an exothermic reaction results and slaked lime is produced which has a chemical

name of Calcium hydroxide. On adding carbon dioxide to a filtered sample of this

liquid, it is found to go cloudy showing that this liquid is in fact Limewater

Rusting

1. What is needed for iron to rust?

Oxygen,

water,

warmth

2. How can it be prevented?

Paint,

galvanise,

oil,

keep it dry,

keep it cold

3. If iron rusts, what will be removed from the air? oxygen

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Safety symbols

Many things around a lab have special signs on them warning you of danger.

Danger

This is a general warning sign. It may be placed in an area where there is some broken glass or a spilt chemical. Or it may just remind you to be particularly careful when doing something or using particular pieces of equipment or chemicals.

Harmful or Irritant

This symbol warns that a chemical may harm your health if you do not use it properly. The word ‘irritant’ means that the chemical may give you a rash if you get it on you or make you choke if you breathe it in.

Corrosive

This symbol tells you that a chemical will attack your skin if you get it on you.

Highly flammable

This symbol warns you that a chemical will catch fire easily.

Risk of electric shock

This symbol means that if used wrongly, the equipment may give you a dangerous electric shock.

Toxic

This symbol means that a chemical is poisonous. Poisons can kill.

Biohazard

This symbol means that there is some type of living thing in an area which may make you ill.

Eye protection must be worn

This symbol reminds you to wear safety glasses or goggles when working in a certain area or using particular pieces of equipment or chemicals.

Wash your hands

This symbol reminds you to wash your hands after you have done an experiment.

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