EdExcel GCSE - Chemistry - Topic 8 - Part II - Fuels and Pollutants

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GCSE Chemistry Flashcards on EdExcel GCSE - Chemistry - Topic 8 - Part II - Fuels and Pollutants, created by Malachy Moran-Tun on 15/03/2021.
Malachy Moran-Tun
Flashcards by Malachy Moran-Tun, updated more than 1 year ago
Malachy Moran-Tun
Created by Malachy Moran-Tun over 3 years ago
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Question Answer
How were Natural Gas and Crude Oil Formed? > Ancient remains of plants and animals > Millions of years, gradually turned into natural gas and crude oil > Not being made anymore (or extremely slowly)
What is Fracking? > Hydraulic fracturing > Way to obtain natural gas and/or other fossil fuels > Water, sand and other substances injected into underground rock
What is a Hydrocarbon? A molecule that contains Carbon and Hydrogen ONLY
What is a Finite Resource? A resource that is NOT made anymore (or made extremely slowly i.e. over millions of years)
What is a Non-Renewable Resource? A resource that is being used faster than it is being made
What is Crude Oil? > Main source of hydrocarbons > Complex mixture of many different hydrocarbons (mostly alkanes)
How can Crude Oil be Separated? > Fractional distillation > Oil heated until most of it has turned into gas > Gas enters a fractionating column > Column has a temperature gradient (i.e. hot at the bottom, cool at the top) > The longer hydrocarbons have higher boiling points so they drain out early on > Shorter hydrocarbons have lower boiling points so they drain out near the top
What are the Main Fractions in Crude Oil (from Shortest to Longest)? > Gases > Petrol > Kerosene > Diesel Oil > Fuel Oil > Bitumen
What are the uses for each (main) Fraction of Crude Oil? > Gases - domestic heating and cooking > Petrol - fuel for cars > Kerosene - fuel for aircrafts > Diesel Oil - fuel for cars and trains > Fuel Oil - fuel for large ships and power stations > Bitumen - surfacing roads and roofs
What is a Homologous Series? A family of molecules which have the same general formula and share chemical properties
What is the General Formula for Alkanes? CₙH₂ₙ₊₂
What are the first 6 Alkanes and their Formulæ? Methane - CH₄ Ethane - C₂H₆ Propane - C₃H₈ Butane - C₄H₁₀ Methylbutane* - C₅H₁₂ Cyclohexane - C₆H₁₂ *aka pentane
Why are the Physical Properties Different in Alkanes / Hydrocarbons? The intermolecular forces are stronger between bigger molecules, which hold the chains of atoms together
Why do Longer Hydrocarbons have Higher Boiling Points? > Intermolecular forces break easier in SMALLER molecules > There is still another place where the force is strong enough to hold in in place > Bonds are harder to break so boiling point is higher
Why are Shorter Hydrocarbons Easier to Ignite? > Shorter hydrocarbons have lower boiling points > The gas molecules mix with oxygen in the air to produce a combustible gas mixture > If the mixture comes in contact with a spark, it will ignite
Why are Longer Hydrocarbons more Viscous? > Viscosity is how easily a substance flows > Stronger force between hydrocarbon molecules > Harder for the liquid to flow - higher viscosity
What is Complete Combustion? Combustion with enough oxygen so only CO₂ and H₂O are produced
What is Incomplete Combustion and why is it Dangerous? > Combustion with limited oxygen > Less oxygen than CO₂ > Produces Carbon Monoxide - CO (toxic gas) > Forms soot (Carbon) > CO can stop blood from carrying oxygen round the body > Soot can cause respiratory problems
What's the Difference between Alkanes and Alkenes? Alkanes - Saturated, they have all single bonds Alkenes - Unsaturated, they have a double bond
What is Cracking? Chemical reaction in which large alkane molecules are split into smaller alkanes and alkenes
Why is Cracking Used? To match supply and demand of hydrocarbons from crude oil - some has a greater demand than what appears in crude oil (also can help make polymers / plastics)
What can Sulfur (SO₂) Dioxide cause? Acid rain (pH below 5.2) since the sulfur dioxide mixes with the clouds to form (dilute) sulfuric acid
What are some problems with Acid Rain? > Damages plants > Issues in ocean wildlife - fish death and coral damage > Damages limestone > Damages marble stonework > Can make metal corrode
What are Nitrogen Oxides produced from? Reactions between nitrogen (N₂) and Oxygen (O₂) in the air, released by combustion reactions (for example, in cars)
Why are Nitrogen Oxides Harmful? They can contribute to acid rain and cause photochemical smog, which is air pollution that can cause breathing problems, headaches, and tiredness
What are the Advantages of using Hydrogen as Fuel? > Very clean > Only waste product is water > No pollutants like CO₂, CO or soot > Obtained from water, which is a renewable resource > The product of water can be reused
What are the Disadvantages of using Hydrogen as Fuel? > Requires a special and expensive engine > H₂ needs to be manufacture, which is expensive and usually requires energy from external sources > H₂ is hard to store
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