chemistry paper 2

What is crude oil formed from?

remains of biomass

what is an alkane ?

a hydrocarbon with single bonds

what are the first 4 alkanes ?

methane , ethane , propane , butane

what happens to hydrocarbons in fractional distillation ?

broken into shorter chains

what is fractional distillation used for ?

producing different fuels

where do the shorteset chain alkanes go in the fractional distillation column ?

rise to the top of the column

what is the viscosity of long chain alkanes ?

high viscosity

do long or short chains have a high boiling point ?

long chains

what size of chain in more volatile ?

short chains

what size of chain is less flammable

long chain

what does combustion release "?

energy

what are the 2 types of cracking ?

Catalytic and steam cracking

what happens in catalytic cracking ?

hydrocarbons vaporised , vapour goes over a catalyst , thermal decomposition takes place , alkanes and alkenes are produced

what happens when alkenes react with bromine water ?

orange to colourless

why can alkenes change the colour of bromine water ?

more reactive

what do alkenes have in terms of carbon bonds ?

a double bond

what are double bond hydrocarbons described as ?

unsaturated

what type of combustion happens when alkenes burn ?

incomplete (smoky flame)

what functional group do alcohol have ?

-oh

what are the first 4 alcholos ?

methanol , ethanol , propanol , butanol

what are 4 properties of alcohol ?

dissolve in water , react with sodium to make hydrogen , burn in air , used a fuel

what happens if ethanol is oxidised ?

ethanoic acid is produced

what is the functional group of carboxylic acid ?

COOH

do carboxylic acids dissolve in water ?

yes

what happens when carboxylic acids form when reacted with carbon ?

carbon dioxide

what is made when carboxylic acids react with alcohols ?

form esters

Why are carboxylic acids weak acids?

dont fully ionise in water

what are the first 4 carboxylic acids ?

methanoic , ethanoic , propanoic , butanoic

what can be added to make polymers ?

alkenes

what join together to form polymers ?

monomers

what is polyethene ?

repeating units of ethene

what turns polymerisation into condensation polymerisation ?

loss of a water atom

what do amino acids form in condensation polymerisation ?

polypeptides and water

what functional groups do amino acids consist of ?

amine group , carboxyl group

how many polymers is dna made from ?

2

What is a pure substance?

only one type of particle

what do pure substances do at a specific temperature ?

boil

can the temperature of boiling of mixtures and elements be used to distugish between the two ?

yes

what are formulations ?

specifically designed mixtures ?

what are some examples of formulations ?

fuels , cleaning agents

what are the 2 phases of chromatography ?

stationary and mobile

what is the stationary phase ?

absorbant paper

What is the mobile phase?

solevant

how does chromatography separate mixtures ?

solevant carries sample

how can you identify different elements from chromatography ?

rf values

what is the chromatography required practical ?

draw base line (pencil) , put known sample on one side and the unknown samples on , dip paper in the solvent, let the solvent travel up the paper , identify the solvent by comparing the known rf values

what is the equation of rf value ?

distance moved by substance / moved by solvent

what is the test for hydrogen ?

burn a splint of tube of gas , squeaky pop if hydrogen in there

what is the test for oxygen ?

put a glowing splint in a tube of gas , relights if oxygen is there

what is the test for chlorine ?

litmus paper , goes white if chlorine is present

what are the flame tests used to identify ?

cations

what colour does lithium go ?

crimson red

What colour does sodium go in a flame test?

yellow

What colour does potassium go in a flame test?

lilac

What colour does calcium go in a flame test?

orange-red

what colour does copper go in flame test ?

green

in the hydroxide test what are the metals reacted with ?

sodium hydroxide

what colour does calcium go in the hydroxide test ?

white

what colour does aluminium go in the hydroxide test ?

white (dissolves in excess)

what colour does magnesium go in the hydroxide test ?

white

what colour does copper go in the hydroxide test ?

blue

what colour does iron (ii) go in the hydroxide test ?

green

what colour does iron (iii) go in hydroxide test ?

brown

how can co2 be identified ?

cloudy lime water

what are added to sulphate ions in the test ?

hydrochloric acid , barium chloride

what colour precipitate does silver chloride form ?

white

what colour precipitate does silver bromide form ?

cream

what colour precipitate does silver idodine form ?

yellow

what is the method for flame tests ?

heat nichrome wire , dip it in acid to clean , dip wire in compound , pass through flame

why are instrumental methods better ?

more accurate

are instrumental methods faster ?

yes

what is flame emission spectrometry used for ?

analyse metal ions

how does fes work ?

light from flame is passed through a spectroscope

what can the line from fes be used to measure ?

concentrations , identify which ions are present

what is the equation for rate of reaction ?

amount used or formed / time

what factors effect the rate of reaction ?

temperature, concentration, pressure, surface area

What do catalysts do?

increase rate of reaction without getting used up

what is the method for measuring the effect of concentration on rate of reaction ?

add hcl to flack , add sodium thiosuphate , swirl to start the reaction , watch the cross disappear , stop time when fully disappeared , repeat using different concentrations

when do reactions occur ?

When particles collide with sufficient energy

what is the minimum energy for a reaction ?

activation energy

how does increasing temp increase collisions ?

gives particles more kinetic energy , collide more frequently

what do catalysts do to the activation energy ?

decrease activation energy

do catalysts provide an alternative reaction pathway ?

yes

what happens in reversible reactions ?

products can form the reactants

how can the directio of a reaction be changed ?

change the conditions

is a reaction exo one way and endo another way ?

yes

what is equalibrium ?

when forward and backward are the same

what does lechatilleurs principle do ?

predicts the effect of changing conditions

what happens the yield in an exothermic reaction if temp is increased ?

yield decreases

what happenes to yeild if pressure of a gass is increased ?

yield decreases

what pwercdentage of the atmosphere is nitrogen ?

80%

what percentage of the is oxygen ?

20

why was co2 more common at the start of the earth ?

volcanic activity

how were oceans formed ?

water vapor condensed

how did oceans remove co2 ?

co2 dissolves into the water

what makes sediment in water ?

carbonates

how did oxygen increase ?

algae and plants produce oxygen (photosythesis)

how do plants remove co2 ?

algae and plants decrease the percentage of c02

What pollutes the atmosphere?

combustion of fuel , carbon emmissions , slufur dioxide (acid rain) , nhydrocarbond particulates

what are reasources used for ?

heat , shelter , food , transport