Chemistry

compound

when two or more elements are joined together

mixture

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

filtration

separates substances insoluble in a solvent from those that are soluble in a solvent

crystallisation

separates a soluble solid from a solvent

distillation

separates a solvent from soluble solids dissolved in the solvent

fractional distillation

way to separate mixtures of miscible liquids

miscible liquids

liquids that dissolve in each other

paper chromatography

a way to separate substances from mixtures in a solution

who invented the plum pudding model

JJ Thompson

who invented the nuclear model

Rutherford

who showed the existence of neutrons in nuclei

Chadwick

number of protons =

atomic number

number of electrons =

mass number - atomic number

isotopes

atoms of the same element with a different number of neutrons

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

diamond

a form of carbon with a giant covalent structure. every carbon atom forms strong covalent bonds with four other carbon atoms, making diamond very hard

bonding of graphite

each carbon atom forms strong covalent bonds with 3 other carbon atoms, forms hexagonal rings, arranged in giant layers.

fullerenes

allow carbon atoms to join together to make large hollow shapes

uses of fullerenes

drug delivery into body as lubricants and catalysts

function of carbon nanotubes

high tensile strength that makes them useful to reinforce composite materials for making tennis rackets. they have delocalised electrons, giving them high electrical conductivity so they’re used in the electronics industry

alloys

mixtures of metals or metals with other elements

why are alloys harder than pure metals

the regular layers are distorted by atoms of different sizes

how does graphite conduct heat and electricity

one electron from each carbon atom is delocalised

percentage yield formula

mass of product produced / maximum mass of product possible

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

percentage atom economy formula

relative formula mass of the desired product / sum of the relative formula masses x 100

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

acids

substances that produce h+ ions when you add them to water

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 revers 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 pressure does the haber process use

200 atmospheres

what is ammonia made from in the haber process

hydrogen and nitrogen

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

sedimentation

solid sediments such as sludge settle out from the mixture

stages of life cycle assessment

raw material extraction, manufacture, use/reuse/maintenance, recycle/waste management

how can metals be recycles

by melting

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