GCSE EDEXCEL CHEMISTRY CORE [C1]

Pregunta	Respuesta
Topic 1 The Earth’s sea and atmosphere	Topic 1 The Earth’s sea and atmosphere
What produced the earth's early atmosphere?	The gases that were produced by the volcanic activity
What did the earth's early atmosphere contain?	A. Little or no oxygen B. A large amount of Carbon Dioxide C. Water Vapour and small amounts of other gases
Why is it difficult to be precise about the evolution of the atmosphere?	No one was actually there at the time, so it's all down to guesswork.
How did the oceans form?	As the earth cooled down, most of the water vapour condensed to form the oceans.
How did the amount of carbon dioxide in the atmosphere get reduced?	A. The Carbon dioxide dissolved into the oceans. B. Marine Organisms developed, which took the Carbon dioxide. When they died the organisms were buried under layers of sediments and the Carbon dioxide became locked up in carbonate rocks.
How did the green plants cause the oxygen level to increase?	The green plants removed carbon dioxide from the air and produced oxygen by photosynthesis.
What is the proportion of oxygen in the atmosphere?	21%
What is the proportion of the gases today in the earth's atmosphere?	Nitrogen - 78% Oxygen - 21% Argon - 0.9% Carbon Dioxide - 0.037% The other gasses are in a much smaller proportion.
How did human activity change the atmosphere?	1) Burning fossil fuels releases CO2 which is a greenhouse gas where the rising levels are causing global warming. 2) Deforestation Contribute to the increase in carbon dioxide. 3) Livestock farming releases huge amounts of methane.
How did Volcanic activity change the atmosphere?	1) Sulfur dioxide can be thrown high up into the atmosphere when volcanoes erupt. Sulfur dioxide gas reacts with sunlight, water, oxygen and dust to form volcanic smog. 2) Carbon dioxide is also released into the atmosphere by volcanic eruptions.
Topic 2 Materials from the Earth	Topic 2 Materials from the Earth
How are igneous rocks formed?	Igneous rocks form when molten magma pushes up into the crust before cooling and solidifying. They contain various different minerals in randomly arranged interlocking crystals.
What are two examples of sedimentary rocks?	Chalk and Limestone
How are sedimentary rocks formed?	Sedimentary rocks are formed from layers of sediment laid down in lakes or seas. After a long period of time, the layers get buried under more layers and the weight pressing down squeezes out water. Fluids flowing through the pores deposit natural mineral cement.
What may sedimentary rocks contain and what are they likely to do?	Fossils and can erode.
What is an example of a metamorphic rock?	Marble
How are metamorphic rocks formed?	Metamorphic rocks are formed by the action of heat and pressure on sedimentary or igneous rocks over long periods of time.
How are marbles formed?	Marble is formed from limestone or chalk. Very high temperatures break down the limestone and it reforms as small crystals. This gives marble a more even texture and makes it much harder.
Where do limestone, marble and chalk exist in and what are they natural forms of?	They exist in the earth's crust and are natural forms of calcium carbonate.
What are the advantages of quarrying limestone?	1) Limestone provides things that people want such as houses and roads. 2) Limestone products are used to neutralize acidic soil. 3) Limestone is also used in power station chimneys to neutralize sulfur dioxide. 4) The quarry provides jobs for people and brings money into the local economy
What are the disadvantages of quarrying limestone?	1) Makes huge ugly holes which ruin the landscape 2) Makes lots of noise and dust in quiet, scenic areas 3) Destroys the habitats of animals 4) Waste materials produce unsightly tips
What is the commercial need in quarrying calcium carbonate?	It produces limestone which is a raw material used to produce other building materials, so it's quarried on a large scale. It gets heated to create cement, concrete and glass.
What is the thermal decomposition of calcium carbonate?	Calcium carbonate gets heated to give out calcium oxide plus calcium dioxide. CaCO3 -> CaO + CO2
What are the three things to remember about atoms?	1) Atoms are the smallest particles of an element that can take part in chemical reactions 2) During Chemical reactions, atoms cannot be created or destroyed. 3) During chemical reactions, atoms are rearranged to make new products with different properties from the reactants.
What is the effect of water on calcium oxide?	When you react calcium oxide with water it produces calcium hydroxide. Calcium hydroxide dissolves in water to produce a solution called limewater.
What is true about the total mass before and after?	The total mass before and after a sealed reaction is unchanged.
Explain how calcium oxide, calcium hydroxide and calcium carbonate can be used to neutralise soil acidity?	Calcium oxide and hydroxide is an alkali which is used to neutralise acidic soil and calcium carbonate can be used to remove acidic gases from coal-fired power stations which reduces emmisions and acidic rain.
Topic 3 Acids	Topic 3 Acids
What acid is produced in the stomach and what does it do?	Hydrochloric acid and it helps digest and kill bacteria's in the stomach.
What are indigestion remedies?	They contain substances such as calcium carbonate which neutralises the excess stomach acid.
How to Investigate the effectiveness of different indigestion remedies?	1) Crust up one dose and dissolve it in water in a conical flask. 2) Add three drops of indicator to the conical flask. This will change colour when the solution has been neutralised. 3) Fill a burette with hydrochloric acid. 4) Using the burette, add the acid to the conical flask a bit at a time, giving the conical flask a regular swirl. 5) The end-point is when the colour change lasts rather than dissapearing after a few seconds. 6) When the indicator changes colour stop adding acid. 7) Read the burette to work out what volume of acid you've added to the alkali. 8) Repeat the experiment three times for each type of tablet and take an average.
What can acids be neutralised by?	1) Metal Oxides 2) Metal Hydroxides 3) Metal Carbonates which produce salt.
What is electrolysis?	1) Electrolysis is the breaking down of a compound using electrical energy. 2) The electricity used comes from a d.c source, such as a battery. 3) It requires a liquid to conduct the electricity, called the electrolyte. 4) The electricity is applied to the electrolyte by two electrodes. 5) The electrolyte contains the compound, which is broken down into its component parts. 6) The component parts are released as atoms or molecules - often as a gas.
How to Investigate the electrolysis of dilute hydrochloric acid	1) The electrolyte is a dilute solution of hydrochloric acid. 2) Applying a d.c current to the electrolyte causes the hydrochloric acid to decompose into its two component parts which are hydrogen gas and chlorine gas. 3) The gases bubble through the solution and can be collected at the electrodes.
How to test for Chlorine?	Chlorine bleaches damp litmus paper, turning it white.
How to test for hydrogen?	Light a splint and if it makes a squeaky pop then hydrogen is present.
Where can Chlorine be obtained from?	It can be obtained from seawater by electrolysis. Chlorine is a toxic gas which can lead to hazards that are associated with it's large-scale manufacture.
What is chlorine used in?	The manufacture of bleach and used to make the polymer poly(chloroethene) - PVC.
Water can be decomposed by electrolysis to form what?	Hydrogen and Oxygen
What is the test for oxygen?	If the gas relights a glowing splint, then oxygen is present.
Topic 4 Obtaining and using metals	Topic 4 Obtaining and using metals
Where are most metals extracted from?	Most metals are extracted from ores found in the Earth's crust. Unreactive metals are found in the Earth as uncombined elements such as gold.
How are most metals extracted from their ores by?	1) Heating with carbon, illustrated by iron. 2) Electrolysis, illustrated by aluminum.
Explain why the method used to extract a metal is related to its position in the reactivity series and cost of the extraction process?	Metals that are less reactive than carbon can be extracted by a reduction reaction with carbon which is done by heating the ore with carbon. Very reactive metals form very stable ores, so if the metal is more reactive than carbon, then it has to be extracted by electrolysis which is expensive.
How to Investigate methods for extracting a metal from its ore?	1) The metal ore is melted and used as the electrolyte for the metal extraction. 2) Electrolysis decomposes the metal oxide into the metal alone and the oxygen atoms. The metal atoms sink to the bottom of the tank as molten metal.
What is Oxidation?	Gain of Oxygen
What is reduction?	Loss of Oxygen
What does the extraction of metals involve?	Reduction of ores
What does the oxidation of metals result in?	Corrosion
What are the advantages of recycling metal?	1) It uses less resources. There's a finite amount of metal in the earth and recycling conserves the resources. 2) It uses less energy as mining and extracting metals needs lots of energy. 3) It uses less money as energy doesn't come cheap, so recycling saves money. 4) It makes less rubbish as recycling cuts down on the amount of rubbish that goes to landfill.
Explain why converting pure metals into alloys often increases the strength of the product?	An alloy is a mixture of two or more metals and different elements have different sized atoms, so the smaller atom of the two will upset the layers of the other atom which makes it more difficult for them to slide over each other which means alloys are harder than pure metals.
Describe how alloying changes the properties of metals?	Smart alloys have a shape memory property where it remembers its original shape. An example of this is nitinol.
Topic 5 Fuels	Topic 5 Fuels
What is a hydrocarbon?	A hydrocarbon is a compound that consists of only hydrogen and carbon.
What is crude oil?	Crude oil is a mixture of hydrocarbons.
What is used to separate crude oil?	Fractional Distillation
What are the uses of the following fraction gases, petrol, kerosene, diesel oil, fuel oil and bitumen?	Gases - Used for cooking and heating. Petrol - Fuel for cars. Kerosene - Used as an aircraft fuel Diesel Oil - Used as a fuel for lorries, trains and some cars. Fuel Oil - Used as a fuel for ships and in some power stations Bitumen - Used to surface roads and roofs.
What is different between the hydrocarbons in the different fractions?	1) The number of carbon and hydrogen atoms their molecules contain 2) boiling points 3) ease of ignition 4) viscosity
What is complete combustion?	When there's plenty of oxygen, hydrocarbons burn to produce only carbon dioxide and water which gives out energy.
What is the test for carbon dioxide?	Bubble the gas through limewater and if it turns cloudy/milky then carbon dioxide is present.
What is incomplete combustion?	Incomplete combustion is where there isn't enough oxygen, so the combustion becomes incomplete. Carbon dioxide and water are still produced however carbon monoxide and carbon are produced as well.
How is carbon monoxide dangerous?	Carbon monoxide is a colourless, odourless and very toxic gas meaning that if you breath it carbon monoxide it could potentially kill you.
Explain why impurities in some hydrocarbon fuels result in the production of sulfur dioxide?	Sulfur impurities are found in petrol and dies
What causes acid rain?	1) Sulfur dioxide is one of the gases that causes acid rain. 2) When the sulfur dioxide mixes with the clouds it forms dilute sulfuric acid. This then falls as acid rain. 3) Acid rain causes lakes to become acidic and many plants and animals die. 4) Acid rain kills trees and damages limestone buildings and ruins stone statues.
What keeps the earth warm?	Various gases in the atmosphere, such as carbon dioxide, methane and water vapour, trap heat from the Sun and that this keeps the Earth warm.
What human activity affects carbon dioxide levels?	1) Deforestation when carbon dioxide is released when trees are burnt to clear land and when there's less trees that means the less co2 that gets taken in, meaning more will be left. 2) Burning fossil fuels
How have scientists been researching ways to restore the balance and limit the increase in carbon dioxide level in the atmosphere?	Iron seeding 1) Iron is an element needed by plants for photosynthesis. Injecting iron into the upper ocean promotes the growth of phytoplankton. 2) These blooms of phytoplankton absorb co2 from the atmosphere for photosynthesis. Converting Carbon dioxide into hydrocarbons
What is an example of a biofuel?	Ethanol which can be obtained by processing sugar cane or sugar beet and that it can be used to reduce the demand for petrol.
What is the advantages of replacing fossil fuels with biofuels?	1) Biofuels are renewable 2) Dead plants needed to make biogas photsynthesised when it's alive which removes co2 from the atmosphere. 3) Cheap and readily available
What is the disadvantages of replacing fossil fuels with biofuels?	1) That growing the crops to make biofuels requires land and may affect the land which is needed to make food. 2) The process requires a lot of energy.
What are the factors that make a good fuel?	1) Ease of ignition - if it burns easily. 2) Energy value - Amount of energy that is released 3) Ash and Smoke - Some fuels leave behind a lot of ash that needs to be disposed of. 4) Storage and transport - Gas needs to be stored in special canisters and coals needs to be kept dry.
What does a fuel cell use?	A fuel cell uses hydrogen and oxygen which forms water and the reaction releases energy.
What are the advantages of using hydrogen, rather than petrol, as a fuel in cars?	1) There are no moving parts, so energy isn't lost through friction. 2) It doesn't produce any conventional pollutants, no greenhouse gases, no nitrogen oxides, no sulfur dioxide, no carbon monoxide. 3) It's a major advantage in cities where air pollution from traffic is a big problem.
What are the disadvantages of using hydrogen, rather than petrol, as a fuel in cars?	1) Hydrogen is a gas, so it takes up loads more space to store than liquid fuels like petrol. 2) It's very explosive, so it's difficult to store safely. 3) The hydrogen fuel is often made from hydrocarbons which are from fossil fuels or by electrolysis of water which uses electricity and the electricity usually gets generated from fossil fuels, so we are still dependent on fossil fuels.
What are the three non-renewable fossil fuels which are obtained from crude oil?	Petrol, kerosene and diesel oil.
What is the non-renewable fossil fuel found in natural gas?	Methane
What are alkanes?	Alkanes are saturated hydrocarbons which are present in crude oil.
What are the formulas for Methane, Ethane, and Propane?	1) Methane - Formula: CH4 2) Ethane - Formula: C2H6 3) Propane - Formula: C3H8
What is used to distunguish between alkane and alkenes and how is it used?	Bromine water and it is used when the substance gets mixed with bromine water and if it doesn't turn the bromine water colourless, still is brown then it is an alkane however if it changes from brown to colourless then it is an alkene.
What is cracking?	Cracking is a form of thermal decomposition which means breaking down larger saturated hydrocarbon molecules, into smaller more useful ones.
Describe the cracking of liquid paraffin in the laboratory?	1) Start by heating the paraffin. After a few seconds, move the Bunsen burner to heat the porcelain chips, alternate between the two until the paraffin vaporises and the porcelain glows red. 2) The heated paraffin vapour cracks as it passes over the heated porcelain. 3) The smaller alkanes and alkenes travel down the delivery tube. 4) The smallest alkanes and alkenes are gases which collect in the gas jar. 5) You can show the gas in the gas jar contains alkenes because it decolourises bromine water.
What is formed when ethene molecules combine together in a polymerisation reaction?	Poly(ethene)
What are the uses of polymers poly(ethene), poly(propene), poly(chloroethene) (PVC) and PTFE to the properties of the compounds?	1) Poly(ethene) is stretchy and light, so it has loads of uses from plastic bags to hose pipes to laminating paper. 2) Poly(propene) is tough but flexible, it can be used for thermal underwear, carpets and even plastic containers. 3) Poly(chloroethene) is flexible and resistant to wear, so it can be used for clothing, electric cables and pipes. 4) Poly(tetrafluoroethene) PTFE is unreactive, flame resistant and very resistant to wear, so it can be used as a non-stick coating for pans.
What are the problems with the disposal of polymers (plastics)?	1) Most polymers are non-biodegradeable, so they don't get broken down by microorganisms, so they don't rot. If you bury them in a landfill site, they'll still be there years later. 2) When you burn polymers, they give off toxic gases
How can some of the problems associated with the disposal of polymers can be overcome?	1) Recycling 2) Developing biodegradable polymers.

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