Chemistry

compound

when two or more elements are joined together

mixture

made up of two or more substances that aren’t chemically mixed together

who invented the plum pudding model

JJ Thompson

who invented the nuclear model

Rutherford

who showed the existence of neutrons in nuclei

Chadwick

how do elements react to form compounds

by gaining, losing or sharing electrons

giant structure/ lattice

where oppositely charged ions formed are held together by strong forces of attraction which act in all directions

covalent bonding

non metal bonding

what do fullerenes do

allow carbon atoms to join together to make large hollow shapes

uses of fullerenes

drug delivery into body as lubricants and catalysts

properties of carbon nanotubes

high tensile strength, delocalised electrons, giving them high electrical conductivity

how does graphite conduct heat and electricity

one electron from each carbon atom is delocalised

why is it not usually possible to get 100% yield from a chemical reaction?

some amounts may be lost when it’s separated or collected from the apparatus

what are titrations used for

to find the exact volumes of acid and alkali that react with each other and to find the unknown concentration of a solution

what happens when group 1 metals react with water

vigorous reaction, giving off hydrogen gas and leaving alkaline hydroxide solutions

what happens when metals react with water or a dilute acid

hydrogen gas is produced

what happens when acids react with a base

a neutralisation reaction occurs, and a salt and water are produced

bases

substances that will neutralise acids

what happens in an aqueous solution at the cathode during electrolysis

the less reactive element, either hydrogen or the metal is produced

what happens in an aqueous solution during electrolysis at the anode

oxygen gas is given off plus water from discharged hydroxide ions or a halogen produced 

why is aluminium oxide mixed with molten cryolite when extracted

to lower its melting point, reducing the energy needed to make aluminium

examples of exothermic reactions

combustion, oxidation reactions, neutralisation reactions

fuel cell

efficient use of the energy from oxidising hydrogen

advantages of hydrogen fuel cells

don’t need to be electrically recharged, no pollutants are produced, can be a range of sizes for different uses

disadvantages of hydrogen fuel cells

hydrogen is highly flammable, sometimes produced by non renewable sources, hydrogen is difficult to store

collision theory

reactions can only happen if particles collide

closed system

where no reactants or products can escape

alkane formula

CnH2n+2

types of cracking hydrocarbons

steam, catalytic

how are esters made

by reacting a carboxylic acid with an alcohol in the presence of a strong acid and catalyst

what is polyester made from

a diol and a dicarboxylic acid

formula for retention factor

distance moved by substance / distance moved by solvent

testing for hydrogen

hold a splint at the open end of the test tube, hydrogen burns rapidly with squeaky pop sound if present

testing for oxygen

insert glowing splint in mouth of test tube, splint relights if oxygen present

testing for carbon dioxide

bubble the gas through limewater/calcium hydroxide, limewater turns milky if present

testing for chlorine

damp blue litmus paper held in mouth of tube, paper is bleached and turns white if present

how can you identify carbonates

by adding dilute acid, which produces carbon dioxide gas, turns limewater milky/cloudy

how can you identify halides

by adding nitric acid then silver nitrate solution

how can you identify sulfates

by adding hydrochloric acid then barium chloride solution, producing a white precipitate of barium sulfate

flame emission spectroscopy

instrumental method that chemists use to analyse samples for metal ions

3 greenhouse gases

carbon dioxide, methane, water vapour

what does reverse osmosis use

membranes to separate dissolved salts from salty water

what is high density polyethene made from

ethene using a catalyst at 50 degrees

what is low density polyethene made from

ethene when using high pressures and a trace of oxygen

what is ammonia used to make

nitric acid 

what’s the most common form of glass

soda-lime

what happens to pure hydrocarbons when they are burnt completely

they are oxidised to carbon dioxide and water

what could incomplete combustion produce in a limited supply of air

carbon monoxide, some unburnt hydrocarbons and particulates that contain soot

what happens during sedimentation

solid sediments such as sludge settle out from the mixture

what is galvanised iron

iron covered with a layer of zinc

why does aluminium metal not corrode

a layer of protective oxide layer forms on it

properties of high carbon steels

very hard but brittle

properties of low carbon steels

softer and easily shaped

alkali

bases that dissolve in water to make alkaline solutions, soluble hydroxide

uses of ammonium nitrate

fertilisers

why can a dye be in different positions during different chromatography experiments

the dye can be more or less soluble in different solutions

what do you call polymers that melt when heated

thermosoftening polymers

why do some polymers not melt when heated

covalent bonds between polymer chains, so high energy required to break them

Phase 1 of evolution of the atmosphere

volcanoes released nitrogen, water vapour, methane, ammonia and carbon dioxide

Phase 2 of the Evolution of the atmosphere

water vapour condensed and formed oceans

What happened to the Carbon Dioxide in Phase 2 of the evolution of the atmosphere

it dissolved in the ocean and formed carbonate precipitates that formed sediments on the seabed

why could more complex life evolve e.g. animals in phase 2

oxygen levels increases

What happened in Phase 3 of the evolution of the atmosphere

green plants produce oxygen and absorb carbon dioxide, increasing oxygen levels and reducing carbon dioxide levels

consequences of climate change

sea levels rising, flooding, changes in rainfall, more storms, temperature changed

ways to reduce carbon footprints

renewable energy, more efficient processes, bury underground, tax

problems of particulates

reflect sunlight back into space so less light reaches the earth, if inhaled can lead to respiratory problems

problems of carbon monoxide

stops blood flowing around body

problems of acid rain

kills plants and aquatic life, makes metals corrode, damages buildings

how is acid rain formed

sulfur or nitrogen oxides mix with clouds to form dilute sulfuric or nitric acid

how is LD Polyethene produced

at a moderate temperature under a high pressure

how is HD Polyethene produced

at a lower temperature and pressure with a catalyst

what is LD Polyethene used in

bags and bottles

what is HD Polyethene used in

water tanks and drainpipes

what do thermosoftening polymers contain

individual polymer chains with weak intermolecular forces

what do thermosetting polymers contain

monomer that can form cross links between the polymer chains

properties of ceramics

insulators of heat and electricity, brittle and stiff

properties of polymers

insulators, easily moulded

properties of composites

depend on the binder and reinforcement used

what is needed to rust iron

oxygen and water

barrier methods to prevent rusting

painting/coating with plastic, electroplating, oiling

sacrificial method to prevent rusting

if a more reactive metal is placed in contact with the iron, it will react with water and oxygen before the iron does

what is bioleaching

where a copper ore is added to a solution with bacteria that can convert copper compounds in the ore into soluble copper compounds. a leachate solution is produced that contains copper ions

what is phytomining

plants are grown in soil that contain copper. the plants can’t get rid of it so the copper builds up in the leaves. the plants are then harvested dried and burned in a furnace. the ash contains soluble copper compounds

stage 1 of the life cycle assessment

getting the raw materials

step 2 of the life cycle assessment

manafacture and packaging

stage 3 of the life cycle assessment

using the product

stage 4 of the life cycle assessment

product disposal

problems of a life cycle assessment

harder to give a numerical value to other effects

what is potable water

water that is safe for humans to drink

what is the difference between pure and potable water

pure water only contains h2o molecules

properties of pure water

boils at 100 degrees, has a ph of 7 and doesn’t contain any dissolved solids

how can water be purified

distillation

stage 1 of sewage treatment

screening

stage 2 of sewage treatment

sedimentation

stage 3 of sewage treatment (lighter liquid)

aerobic digestion, air is pumped through to make aerobic bacteria to break down the organic bacteria

stage 3 of sewage treatment (anaerobic digestion)

organic matter is broken down by bacteria which releases methane gas

what temperature and pressure does the haber process use

450 degrees and 200 atmospheres

what does an acid + base make

salt + water

what does an acid + metal oxide or hydroxide make

a salt + water

what does an acid + metal carbonate make

salt + water + carbon dioxide