C3 Quiz

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Flashcards by harry.vinall, updated more than 1 year ago
harry.vinall
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GCSE Chemistry (C3) Flashcards on C3 Quiz, created by harry.vinall on 04/08/2014.

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Question Answer
What can geologists determine by studying rocks? When, where and how rocks were formed; this tells us the land that makes up Britain today has, over millions of years, moved over the surface of the earth
Describe how Britain was 'made' when a supercontinent was formed? 600 million years ago Britain wasn't in one piece, England and Wales were in a different continent to Scotland and were separated by an ocean; gradually the continents moved towards each other and crashed to form a supercontinent, this joined England and Scotland and built a range of mountains
What happened after the supercontinent formed? (include how three substances were formed) The supercontinent then moved northwards and the climate changed. Deserts formed red sandstone; tropical swamps with rainforest produced coal and chalk formed in the warm seas. 60 million years ago the North Atlantic Ocean began to open up taking North America away from Europe and causing volcanoes to erupt along the western edge of Scotland. Ice ages during the last 3 million years brought glaciers down from the north eroding the highlands of Scotland, northern England and Wales.
How can the variety of rocks in Scotland be explained? Igneous rocks are formed in Scotland due to magma (from when the atlantic opened up) solidifying. As these rocks solidify the magnetic material records the direction of the magnetic north, when the rocks move (through continental drift) this changes. In addition the position of the magnetic north changes over millions of years. Rocks in Scotland that formed at different times and different places therefore have different magnetic directions, showing that at one point the country was in 5 separate chunks.
What resources are there in north-west England that make it important to the chemical industry? Coal in south Lancashire, salt in Cheshire and limestone in the Peak District
How was limestone in the peak district formed? 350 million years ago, north-west England covered by sea. Calcium compounds in the ocean reacted with carbon dioxide in the air to form calcium carbonate, this formed sediment which got crushed into sedimentary rock, limestone.Other rocks were laid down on top. 300 million years, tectonic plate movements pushed limestone up to form mountains. Gradually the rocks above were eroded until limestone was exposed below.
How was coal formed in Lancashire? 290 million years ago Lancashire was a warm, wet swamp on the edge of a sea where trees and other plants died in abundance. They became buried under sediment and their carbon content gradually turned into coal.
How was salt formed in Cheshire? 200 million years ago Cheshire was covered by a shallow sea. Rivers flowing into the sea carried salts dissolved from rock. The climate grew hot and dry so the sea evaporated, leaving the salt mixed with sand blown in from surrounding deserts. Later other sediments were deposited over rock salts burying it.
What evidence is there to support ideas about the formation of limestone, coal and salt? Coal contains fossils of plants that formed it, limestone contains bits of shell and fossils of other sea creatures that lived in the sea when the sediment was formed. Rock salt contains small, rounded sand grains which tells geologists they were carried by the wind, if they were from the water they would be larger and rougher.
What are some uses of salt? Grit roads, salt water has a lower freezing point so won't turn to ice, also sand in rock salt helps vehicles grip the roads. Can also be used in chemical industry.
How is salt for the chemical industry obtained and what problems can this cause? Water pumped into underground salt deposits, dissolves to form a concentrated solution called brine. This is pumped to the surface and piped to where it is needed, this is called solution mining. This can be convenient however it can leave large holes underground causing the ground to sink; salt can infiltrate drinking water supply; plants die if soil is contaminated by salt
What are the benefits and risks of eating salt? Benefits: food tastes nicer, preserves food. Risks: raises blood pressure can lead to health conditions (e.g. stroke)
Give four uses of alkali Making salt (mix ashes of burnt wood with animal fat and water; boil; add fat. Soap forms layer on the surface) Neutralising soil (lime (calcium oxide), seaweed ash used) Making glass (Lime and seaweed mixed with sand to make glass) Dyeing cloth (ammonia, found in urine, reacts with alum to form aluminium oxide; this binds the cloth to the dye, so it won't be washed out)
What is the difference between an alkali and a base? An alkaline solution is one with a pH of greater than 7, turning litmus paper blue. Two groups of substances form alkalis when dissolved in water: soluble carbonates and hydroxides. Carbonates and hydroxides which are not soluble are called bases, they react with acids in a similar way to alkalis but do not affect indicator.
What the general patterns of the reaction of alkalis with acids? hydroxide + acid = salt + water carbonate + acid = salt + water + carbon dioxide
Name three types of salt and the acid they are associated with. Chloride- hydrochloric; sulphate- sulphuric; nitrate- nitric
Describe the Leblanc process and outline the problems it cause. The method made alkali by reacting salt with sulphuric acid and then heating it with coal and limestone. This created sodium carbonate but also gave off huge amounts of hydrogen chloride gas and produced huge heaps of solid gas called galligu. Tall chimneys were built to try and disperse the hydrogen chloride gas but most sank into the ground and killed plants and animals. The galligu gave off stinking and poisonous 'bad egg' fumes of hydrogen sulfide.
How was the problem of hydrogen chloride in the Leblanc process countered? How was the product then turned into bleach? By dissolving the hydrogen chloride in water to make hydrochloric acid. The following reaction was then used to extract chlorine, which was used as a bleach: hydrochloric acid + manganese dioxide = chlorine + manganese chloride + water.
What are the benefits and risks of using chlorine in water? Benefits: disinfect water killing harmful microorganisms Risks: toxic gas can affect human health if too much is present in water, disinfectant by-products are formed that are toxic if chlorine reacts with organic materials in the water supply.
Define electrolysis Process by which electricity is passed through a molten salt or a solution of a salt. This causes chemical changes to take place.
Describe what happens in the electrolysis of brine. Brine is a concentrated sodium chloride solution. Brine is pumped into a membrane cell. Electricity enters the solution through two electrodes. Chlorine gas is given off and collected at the anode, positive electrode. Hydrogen gas is given off and collected at the cathode, negative electrode. Sodium hydroxide is left in the solution. Water is added to the membrane cell and the sodium hydroxide solution is piped off. .
What impacts can the electrolysis of brine have on the environment? Chloride is toxic and corrosive, sodium hydroxide is a powerful alkali and hydrogen is flammable.
Suggest risks that industrial chemicals pose. Can be absorbed by plants and passed up food chain; animals may not be able to excrete some chemicals until they reach dangerous concentrations; humans can then eat these animals/plants posing a serious risk to human health.
What is PVC A polymer containing carbon, hydrogen and chlorine. PVC is a stiff, tough material that can be heated and moulded into any shape. It has many uses in buildings. Plasticisers are added to PVC to make them softer and more flexible so it can be used for wires and cables.
What is the risk of PVC Plasticised PVC can leach their plasticiser molecules, it is thought these could be harmful to fish if they are leached into rivers or the sea. It also gives off highly toxic gases when it burns and it's production creates toxic byproducts.
What is a Life Cycle Assessment (LCA)? An assessment that adds up all the effects that a product has on the enviroment.
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