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Chemistry - c1 gcse

edexcel science

QuestionAnswer
Which gases would have beem in the Earth's early atmospehere due to volcanoes? Carbon Dioxide, Water vapour, Ammonia, Methane and Nitrogen.
Which planets do scientists think are like Earth's early atmosphere due to their volcanoes? Mars and Venus.
What evidence is there to suggest that there was little to no oxygen in the Earth's atmosphere? Volcanoes do not release oxygen and some iron compunds in the Earth's oldest rocks could not have been formed with Oxygen around.
Why are there uncertainties about the theories on Earth's early atmosphere? As we have only limited evidence on the Earth's atmosphere when it was young.
As the Earth colled the water vapour condensed to form the Oceans, what gas from the atmosphere then dissolved in it? Carbon Dioxide.
How did the Carbon Dioxide eventually come to be found in Limestone as Calcium Carbonate? Marine organsims used the dissolved carbon dioxide to make shells of Calcium Carbonate. Once these died their shells fell and became sediment which was then compressed with layers and layers forming limestone (sedimentary rocks.)
How did the Earth's atmoshpehere loose more of it's Carbon Dioxide and gain Oxygen? Organisms developed the ability to photosynthesise (mainly the stromatolites) which took in the Carbon Dioxide and released Oxygen.
What gas is there most of in the Earth's atmosphere today? Nitrogen, 78%.
What percent of the Earth's atmosphere today is Oxygen? 21%.
How are Igneous rocks formed and describe it's qualities? Formed from Magma or Lava that has cooled down. Has interlocking crystals that vary in size.
How are Sedimentary rocks formed and describe it's qualities? Formed when layers of sediment are compressed. It is layered and has rounded, weakly joined grains, is porous.
How are Metamorphic rock formed and describe it'squalities? Formed when heat or pressure change other rocks. Has hard interlocking crystals.
Give some examples of Igneous rocks. Basalt, Granite and Obsidian.
Give some examples of Sedimentary rocks. Sandstone and Limestone.
Give some examples of Metamorphic rocks. Marble, Slate and Gnesis.
When Igneous rocks cools slowly underground, what size are the crystals? Large crystals.
Thermal decomposition - What are the products of heating Calcium Carbonate (limestone) CaCO3(s)? Calcium Oxide - CaO(s) and Carbon dioxide - CO2(g).
The thermal decomposition of Limestone is used in the manufacture of what? Cement, Concrete and Glass.
What is a precipitation reaction? A reaction where an insoluble product is formed from soluble reactants.
Balance this equation: S8 + O2 -> SO3. S8 + 12O2 ->8SO3.
Atoms are not created nor destroyed in a chemical reaction - they are only rearranged. This means that the total what is the same before and after the reaction? The total mass is the same.
When you add an Acid with and Alkali their pH becomes closer to 7, what is this called? A neutralisation recation.
What is the test for Carbon Dioxide? Test it in Limewater, if there is Carbon Dioxide the Limewater turns cloudy.
If your stomach produces to much acid it can cause indigestion. What acid does your stomach produce? Hydrochloric acid.
Antiacids can neutralise excess stomach acids, what are they made of? Bases.
Give some examples of Hazard symbols. Corrosive, Caution (harmful or irritant), Flammable and Toxic.
What are the products when you neutralise Hydrocholiric acids? Chloride salts and water.
What are the products when you neutralise Nitric acid? Nitrate salts and water.
What are the products when you neutralise Sulphuric acid? Sulphate salts and water.
Acid + Metal oxide -> ? Salt + water.
Acid + Metal hydroxide -> ? Salt + water.
Acid + Metal Carbonate -> ? Salt + water + carbon dioxide.
Compounds can be decomposed into their original elements using electricty, what is this called? Electrolysis.
Chlorine is a yellow/green toxic gas, what are some of it's uses? To bleach paper, in cleaning products and to kill microorganisms to treat our water supply.
How can you test for Chlorine? With blue litmus paper, it will firstly turn red as Chlorine is an acid, it will then turn white as the Chlorine will bleach it.
In the electrolysis of water what element will go to the positive electrode (Anode)? Oxygen (02).
In the electrolysis of water what element will go to the negative electrode (Cathode)? Hydrogen (H2).
How do you test for Hydrogen? Place a lighted splint on the gas and if the gas is Hydrogen it will produce a squeky 'pop'.
How do you test for Oxygen? Place a splint that is just glowing on the gas, if it is Oxygen the splint will relight.
What is an ore? An Ore is a rock from which you can extract enough metal for a profit.
What is the name of the process during which we take metal from an ore? Extraction.
Name one way in which some metals can be extracted from it's compound and the chemical equation which can occur. Some metals can be extracted by heating their compounds with Carbon. Iron oxide + carbon -> iron + carbon dioxide.
Name another way in which metals that are more reactive than Carbon can be extracted from it's compound and the chemical equation which can occur. Some metals can be extracted by electrolysis. Aluminium oxide -> aluminium + oxygen.
What is an effect of a metal being more reactive? Its is harder and more expensive to extract.
What is Reduction? Reduction is the removal of Oxygen. e.g.: Iron oxide + carbon -> Iron + carbon dioxide.
What is Oxidation? Oxidation is the addition of Oxygen. e.g.: Aluminium + Oxygen -> Aluminium oxide.
Most metals corrode by reacting with oxygen and sometimes water, which type of metal corrode quicker? More reactive metals corrode quicker. This means they lose their properties and their usefulness.
What advantages are their of recycling metals? - Natural reserves of metal ores will last longer. - For most metals recycling uses less energy than extracting. - Reduces need to mine ores. - Reduces pollution caused by extraction. - Less metals are disposed of in landfill sites.
How are Iron and steel seperated from other metals for recycling? By large magnets as they are magnetic.
What are the properties of metals? Metals conduct heat and electricity. they are malleable (can be hammered into shape) and ductile (can be streched into wires). They are also shiny when polished as well as often very strong.
What are the properties of Aluminium? Aluminium has low density, does not corrode as it is protected by a layer of aluminium oxide that forms quickly on its surface.
What are the properties of Copper? Copper is an excellent electrical conductor. Copper has a low reactivity and does not react with water.
What are the properties of Gold? Gold is very, very unreactive so does not corrode. Gold is attractive and remains shiny as it does not tarnish from corrosion. One of the best metal electrical conductor but is very expensive.
What are the properties of Iron and Steel? Pure iron is too soft so is often made into steel which is a mix of iron with carbon and various other metals. This is stronger and harder than regular iron.
What is an alloy? An alloy is a mixture of metals. It is normally made to improve their properties for a specific purpose.
Why are alloys stronger than pure metals? This is because in a pure metal all the atoms are the same size so the layers can slide over each other, making the metal soft. However in an alloy there are different sized atoms which prevent layers sliding over each other as it jams the slide.
What is a shape memory alloy? Shape memory alloys if bent out of shape will return to their original shape once heated. An example is Nitinol.
What is Nitinol an alloy of? Nickel and Titanium.
How is Crude oil formed? Crude oil is formed over millions of years from sea plants/animals. Once died they fell onto sea-bed and were buried under sediment which kept away oxygen, preventing them decaying.Sediments built up,causing heat and pressure which made crude oil.
What is some facts about crude oil? Crude oil is a fossil fuel and is a mixture of different hydrocarbons. It is a non-renewable resource and often contains impurities like sulphur.
What does fractional distillation do? It seperate the crude oil into simpler mixtures of similar hydrocarbons with a more limited range or carbon atoms in the molecules than in crude oil. It is done in an oil refinery.
How is fractoinal distillation done? The crude oil is boiled and the vapour condenses on different levels, dependent on it's boiling point. This take place in a tower hot at the bottom and cooler at the top.
What are the fractions of crude oil, from top of the tower to the bottom? Gases, Petrol, Naphtha, Kerosene, Deisel oil, Fuel oil and Lubricating oil, Bitumen.
What appens to the fractions as we go lower in the fraction tower? They have more molecules, harder to ignite, have a higher boiling point and are more viscous (thick and sticky liquids).
What is the word equation for when a hydrocarbon fuel has complete combustion? Hydrocarbon + Oxygen -> Carbon dioxide + Water
What causes incomplete combustion? If the burning fuel does not have enough Oxygen incomplete combustion occurs.
What can be the products of incomplete combustion? Carbon (soot), Carbon monoxide or both with Carbon dioxide.
What are the problems with Carbon monoxide? It is a colourless, odourless toxic gas, so can be evry dangerous.
What are the problems Carbon (soot)? Can clog appliances such as boilers, or if produced by cars can ge into poeple's lungs by air and could cause lung diseases.
What is Acid rain? Acid rain is rain that is more acidic than normal with a pH that is lower than 5.2.
What causes Acid rain? Hydrocarbon fuels with impurities such as Sulphur are burnt. The sulphur reacts with the Oxygen in the air forming sulphur dioxide. This then dissolves in the rainwater to make it more acidic and into substances such as sulphurus acid and sulphuric acid.
What are the effects of Acid rain? - Makes rivers/lakes/soil more acidic harming organism and crops. - Damages trees. - speeds weathering of limestone/marble buildings and speed the corrosion of metal.
Carbon dioxide, Methane and water vapour are greenhouse gases. What are greenhouse gases? Greenhouse gases trap heat energy and help to keep the Earth warm.
What is iron seeding? Adding iron compounds to ocean -> Used by microscopic plants to grow -> They take in Carbon dioxide from atmosphere -> Eaten by sea creatures -> die sink to ocean floor -> Carbon in shells buried, removed from atmopshere for a long time.
What is another way (except iron seeding) to reduce the amount of carbon dioxide in the atmnosphere? By capturing the carbon dioxide from fossil fuelles power stations and reacting it to make hydrocarbons to then be used again as fuels.
What are biofuels? Biofuels are obtained from living organisms or organisms that have recently died. E.g. wood, dried animal droppings or Ethanol (wheat, sugar cane or sugar beet).
Biofuels are "Carbon neutral", what does this mean? Carbon neutral means that the fuel does not add any carbon dioxide to the atmosphere overall.
What makes a good fuel? - How easily it burns. - How much energy it produces. - How easy it is to store and transport.
What is an Alkane molecule? An alkane molecule is when each carbon in the hydrocarbon molecule is bonded to four other atoms with single bonds. These are also called saturated hydrocarbons.
What is an Alkene molecule? An alkene molecule is when each some atoms in the hydrocarbon molecule have double bonds between them. They are also called unsaturated hydrocarbons.
How does the Bromine test work? Bromine is dissolved in water and is usually orange. If it is mixed with a saturated hydrocarbon (Alkane) there is not colour change. If it is mixed with an unsaturated hydrocarbon (Alkene) it decolorises and become a colourless liquid.
What is the chemical composition of Methane? CH4.
What is the chemical composition of Ethene? C2H4.
What is the chemical composition of Propene? C3H6.
What is the chemical composition of Butane? C4H10.
What is the chemical composition of Pentane? C5H12.
What is cracking? Cracking is when longer hydrocarbons are split into sorter, more useful hydrocarbons. Long chained alkanes are heated and through thermal decomposition become shorter chain alkanes and alkenes.
Why is cracking done? So that the longer chained hydrocarbons which have more supply than demand will still be useful by becoming the shorter chained hydrocarbons for which there is greater demand than supply.
What is a polymer? A polymer is a long chained molecule made by joining many small simple molecules(monomers) together.This happens in polymerisation.
What are the problems with polymers? They are not biodegradable which means they last a long time but also means it will not rot once thrown away. There is also difficulty incinerating polymers as plastics produce toxic sustances when they burn. These must be removed and safely disposed.
How can we help this problem with polymers? We can use less material, as well as reuse the polymers and recycle them. However recycling can be slightly problematic as the polymers have to be sepereated into different types of polymers.
Created by: grabm