chemistry test summer

Chapter 9 - Crude oil and Fuels Chapter 11.1 - Addition polymerisation only Chapter 13.1 and 13.2 - History of our atmosphere and our evolving atmosphere only Chapter 2.6 - The transition elements only

what is crude oil

a mixture of hydrocarbons. hydrocarbons are made up of hydrogen and carbon atoms only.

what are alkanes

a type of hydrocarbon which come from crude oil.

what type of bonding do hydrocarbons undergo

covalent bonding

displayed formula of methane and molecular formula

CH4

displayed formula of ethane and molecular formula

C2H6

displayed formula of PROPANE and molecular formula

C3H8

displayed formula of butane and molecular formula

C4H10

example of covalent structure of ethane

formula for finding out how many carbon/hydrogen atoms in an alkane

n=number of atoms

pattern in molecular formulas of alkanes

saturated hydrocarbons

have a single bond between the carbon atoms. alkanes are saturated hydrocarbons.

whats a homologous series

• series of compounds increasing in size, which exhibit similar chemical properties and trends in physical properties

• alkanes are a homologous series as you just add CH2 each time.

IMPORTANT: crude oil is a fossil fuel. describe how crude oil is separated into fractions. (4 marks)

• crude oil is heated to evaporate the substances

• the fractionating column is hotter at the bottom and cooler at the top

• the vapours condense at their different boiling points/ fractions.

whats combustion

another word for burning. reacting with oxygen.

two types of combustion

complete and incomplete combustion

general formula of complete combustion

general formula for incomplete combustion

hydrocarbon+ (limited) oxygen ➔ carbon monoxide+ water

OR

hydrocarbon ➔ carbon+ water

chemical formula for carbon monoxide

CO

why is carbon monoxide dangerous

• colourless and odorless

• your red blood cells pick it up and carry it around your body instead of o2.

difference between alkenes and alkanes

alkanes have only single bonds between carbon atoms, making them "saturated". Alkenes contain at least one carbon-carbon double bond, making them "unsaturated".

example of alkene ethene

whats cracking

• thermal decomposition

• large hydrocarbons are not as useful as theyre not as flammable

• therefore we need a method of turning large hydrocarbons into smaller ones

• this is called cracking

example diagram of cracking hydrocarbons

why do alkenes even exist?

after cracking, some of the molecules dont have 4 bonds, so it cant make 2 alkanes. instead it makes one alkene and one alkane.

when drawing a diagram of an alkene/ alkane, how many bonds does each carbon atom always need to have

4 as carbon is in group 4.

how many molecules can cracking produce

cracking can produce 3 molecules. one is always an alkane and the rest are alkenes.

what are the two ways to crack large alkanes?

• catalytic cracking

• steam cracking

catalytic cracking

• uses a catalyst

• moderate temp (arnd 500 c) and pressure

• more energy efficient

steam cracking

• uses high temp (arnd 750 c) and high pressure

• uses steam and very high heat without catalyst which produces more alkenes.

test for alkenes

orange bromine water turns colourless when addwhatsed to alkenes. it stays orange when added to alkanes

monomers and polymers

monomers- small molecules

polymers- large molecule made of a chain of monomers

e.g. plastics are made up of lots of small molecules joined together.

whats addition polymerisation

when long chain molecules are formed from lots of small molecules joining togethe with no other products.

all covalent bonds.

example of a monomer and a polymer

monomer= ethene

polymer= poly(ethene)

properties and uses of polymers

properties- strong, easy to shape, transparent

uses- plastic bags, bottles, cling film

example diagram of addition polymerisation

example of displayed formula of monomer vs polymer

how to do displayed formulas of polymers with more than 2 carbons

are alkanes and alkenes both monomers

no only alkenes.

condensation polymers

monomers join together to make polymers and another small molecule is given off, often water,

examples of structures of monomers, polymers and names and repeating units

whats earths atmosphere made up of today?

78% nitrogen

21% oxygen

0.9% argon

0.04% carbon dioxide

earths early atmosphere

volcanoes released:

• co2

• water vapour

• nitrogen gas (N2)

• traces of methane (CH4)

• traces of ammonia (NH3)

THERE WAS NO OXYGEN

evidence for early atmosphere

• gas bubbles trapped in ancient rocks (more reliable)

• data from atmospheres of other planets and their moons in the solar system

why did the co2 from the early atmosphere decrease to only 0.04% today

• water vapour from volcanoes condensed to rain

• convected in the earths crust + produced large bodies of water

• co2 dissolved into these bodies of water out of the atmosphere

• also went down due to photosynthesis and forming carbonate rocks

why did methane/ ammonia level of early atmosphere go down?

• o2 reacted with methane+ ammonia

• o2 also would have reacted with metals to form metal oxides

whats the ozone layer

• ozone (O3) forms a layer in upper atmosphere

• absorbs harmful UV radiation from sun + protects organisms on earth

issues with burning alkanes

• release CO2 which s greenhouse gas + contributes to global warming

• might release carbon monoxide which is a toxic gas

• might release carbon which can cause respiratory problems

greenhouse gases

• carbon dioxide, CO2

• methane, CH4

• water vapour, H2O

• nitrous oxide, N2O

the greenhouse effect (memorise)

1. sun emits radiation to earth

2. greenhouse gases let short-wavelength radiation pass through atmosphere to earths surface

3. this is absorbed by earth+ causes earth to be heated

4. surface of the earth cools down by emitting longer wavelength radiation

5. greenhouse gases absorb infrared radiation (long wavelength radiation)

6. higher the proportion of greenhouse gases in air, more energy is absorbed

7. so some of the energy radiated from surface of earth gets trapped in atmosphere+ temp rises

climate change

• based on peer reviewed info, many scientists believe that human activities will cause temp of earths atmosphere at the surface to rise and this will result in a global climate change.

why has the levels of CO2 released into the atmosphere increased in past 60 yrs?

mainly fossil fuels+ deforestation

some of CO2 does still dissolve into oceans but as temp rises, co2 becomes less soluble so this happens less.

why are there now increased levels of methane?

• more animal farming leading to more emissions and decomposing waste

• also, increased waste, so more decomposition of rubbish in landfill sites.

nitrogen oxide formula-

NOx

theres an x because it can have any number of O and will still be nitrogen oxide. e.g. NO, NO2, NO3 ect.

problems of acid rain

• damage to trees

• damage to buildings/ statues

• damage to aquatic animals

particulates

• tiny particles containing carbon

• diesel engines burn hydrocarbons

• they react with o2 but dont burn completely (incomplete combustion)

• tiny solid particles and unburnt hydrocarbons are produced. these are particulates.

• they get carried into the air and casue global dimming

• they damage our lungs and cause cancer.

how is CO2 formed, potential problems, + ways to reduce problems

formed- complete combustion

problems- global warming

solutions- burn less fossil fuels

how is carbon monoxide formed, potential problems, + ways to reduce problems

formed- incomplete combustion

problems- toxic, colourless and odourless (hard to detect)

solutions- ensure good O2 supply when burned

how is carbon formed, potential problems, + ways to reduce problems

formed- incomplete combustion

problems- global dimming+ respiratory issues

solutions- ensure good O2 supply when burned

how is sulfur dioxide formed, potential problems, + ways to reduce problems

formed- combustion of sulfur in fuel

problems- acid rain ( damages 🌳, 🐟, 🏠)

solutions- remove sulfur from fuel before burning

how are nitrogen oxides formed, potential problems, + ways to reduce problems

formed- combustion at high temps (often in engines)

problems- acid rain/ respiratory issues

solutions- for engines use a catalytic converter

how is unburnt fuel formed, potential problems, + ways to reduce problems

formed- not all fuel burnt

problems- harmful and a greenhouse gas

solutions- ensure correct fuel-to-air ratio when fuel is burned

transition metals

• located in the middle of the periodic table

• properties are generally same as normal metals- e.g. shiny, malleable

• they form many ions

• less reactive than group 1 metals. they react slowly, if at all.

use of transition metals

• can be used as catalytic converters in vehicles- they help to convert harmful gases in vehicle exhaust fumes into less harmful ones

the reaction that produces rust

iron+ water+oxygen➔ iron oxide

inert

• inert= very unreactive/ dont react

• gold, silver and platinum are all very inert which is why they are used in jewellery

products of transition metals

when they react, alkali metals tend to produce white compounds, but when transition elements react, they produce coloured ionic compounds.

e.g. copper sulphate is bright blue. copper is a transition metal.