Topic 8 - Fuels And Earth Science Flashcards
What are hydrocarbons?
Compounds that contain carbon and hydrogen only
What is crude oil?
A complex mixture of hydrocarbons containing molecules in which carbon atoms are in chains or rings.
It’s an important source of useful substances and a finite resource.
How is crude oil separated into simpler + more useful mixtures?
By fractional distillation- oil is heated until most has turned into gas. Gases enter fractionating column. In column there’s temperature gradient. Longer hydrocarbons with HBP turn back into liquids + drain out column near bottom. Shorter hydrocarbons turn to liquid + drain out near top where it’s cooler.
What are the 6 fractions separated from crude oil?
Gases Petrol Kerosene Diesel oil Fuel oil Bitumen
What is the acronym for the 6 fractions?
Glamorous People Keep Dogs For Babies
What are the uses of gases?
Used in domestic heating + cooking
What are the uses of petrol?
Used as a fuel in cars
What is the uses of kerosene?
Used as a fuel in aircraft
What are the uses of diesel oil?
Used as a fuel in sound cars and larger vehicles eg trains
What are the uses of fuel oil?
Used as a fuel for large ships and in some power stations
What are the uses of bitumen?
Used to surface roads and roofs
What are the properties of shorter hydrocarbons?
Intermolecular forces break a lot more easily therefore have lower BP
Easy to ignite so usually gases at room temp
Low viscosity and are much runnier
What are the properties of longer hydrocarbons?
Strong intermolecular forces therefore have high BP
Hard to ignite
Liquids at room temp
High viscosity + thick
What is a homologous series?
Series of compounds which have the same general formula. Differ by CH2 in molecular formulae from neighbouring compounds. Show a gradual variation in physical properties. Have similar chemical properties.
What do complete combustion reactions of hydrocarbons produce?
Carbon dioxide + water. Energy is given out.
Explain what the incomplete combustion of hydrocarbons can produce
Carbon and carbon monoxide due to lack of oxygen.
How does carbon monoxide act as a toxic gas?
It can combine with red blood cells + stop your blood from carrying oxygen around the body. This cane lead to fainting, coma or death
What are the problems caused by incomplete combustion?
Particles of carbon can be released into atmosphere. When they fall back to ground they deposit themselves as soot on buildings. Reduces air quality leading to respiratory problems.
Explain how impurities in some hydrocarbon fuels result in the production of sulfur dioxide
When fossil fuels are burned they release sulfur dioxide (SO2) which comes from the sulfur impurities in the fossil fuels.
How is acid rain caused?
When sulfur dioxide mixes with clouds is forms dilute sulfuric acid which falls as acid rain.
What are the problems with acid rain?
Causes lakes to become acidic + plants + animals die. Also kills trees and damages limestone buildings
What are the non renewable fossil fuels obtained from crude oil?
Petrol, kerosene, diesel oil + methane found in natural gas.
Why are nitrogen oxides produced when fuels are burned in engines?
Caused by the internal combustion of engines in cars - nitrogen + oxygen in air react.
What is bad about nitrogen oxides being produced from engines?
They’re harmful pollutants - can contribute to acid rain + photochemical smog which is air pollution that can cause breathing difficulties
What are the advantages of hydrogen being used instead of petrol in cars?
Very clean
Only waste product is water
Obtained from water which is renewable
What are the disadvantages of using hydrogen instead of petrol in cars?
Need a special expensive engine
Expensive to manufacture + uses energy from another source
Hard to store + not widely available
Very reactive
What is cracking?
breaking down of larger, saturated hydrocarbon molecules (alkanes) into smaller, more useful ones, some of which are unsaturated (alkenes)
Why is cracking used/necessary?
Lots of the longer molecules produced from fractional distillation are cracked into smaller ones as there’s more demand for products like petrol + diesel than bitumen + fuel oil
What formed the earths early atmosphere?
Gases like CO2, steam, methane + ammonia produced by volcanic activity
What was the earths early atmosphere thought to contain?
Little/no oxygen as there wasn’t any plants
Large amount of CO2 + water vapour from volcanoes erupting
Small amounts of other gases (methane + ammonia)
How did the condensation of water vapour form oceans?
As the earth started to warm up the water vapour evaporate, cooled + condensed to create clouds which then rained down + formed oceans.
How did the amount of CO2 in atmosphere decrease?
Lots of CO2 dissolved into the oceans
How did the amount of oxygen in the atmosphere increase?
Primitive plants photosynthesised + removed CO2 + produced oxygen. Oxygen gradually built up and much of the CO2 got locked in fossil fuels + sedimentary rocks.
Describe the chemical test for oxygen
Take a glowing splint and place it into a test tube. If it relights oxygen is present.
What is the greenhouse effect?
1- earth radiates some heat radiation as infrared radiation (IR)
2- some IR absorbed by greenhouse gases
3- some IR is reflected back to Earth by greenhouse gases
4- some IR is re emitted to space
5- absorption + reflection of IR by greenhouse gases is what keeps Earth warm
What are greenhouse gases?
Gases in atmosphere that absorb + reflect heat radiation. Present in small amounts. Carbon dioxide, methane + water vapour are 3 gg
