Unit 3 Flashcards
why do metals conduct electricity?
because the outer electrons are delocalised (free to move)
what is a metallic bond?
the electrostatic force of attraction between positively charges ions and their delocalised electrons
complete the equation
metal + oxygen =
metal oxide
complete the equation
metal + water =
metal hydroxide + hydrogen
complete the equation
metal + acid =
salt + hydrogen
how can metals be used to make soluble salts?
excess metal is added to the correct acid
mixture is filtered to remove unreacted metal
filtrate is evaporated to dryness
what is reduction?
gain of electrons
what is oxidation?
loss of electrons
what is a redox reaction?
when both oxidation and reduction take place at the same time
when a metal is extracted from its ore is a metal being oxidised or reduced?
reduced
what is an ore?
a compound containing useful amounts of metal ions
what happens to a metal ion when they are being extracted from metal ores?
they gain electrons to change from ions to atoms
how are very reactive metals obtained from their ores?
electrolysis
how can very unreactive metals be obtained from their ores?
by heat alone
how are most metals extracted from their ores?
heating with carbon or carbon monoxide
what is electrolysis?
the breaking of an ion compound into its elements using electricity
why must a D.C. supply be used for electrolysis?
to allow the elements to build up at the electrodes for identification
what happens at the electrodes during electrolysis?
positive ions gain electrons at the negative electrode
negative ions lose electrons at the positive electrodes
how do you make a current flow using two different metals in a solution of their own ions? (2 half cells)
connect the metals with a wire
connect the solutions with a salt bridge
the electrons will flow along the wire
why does graphite make a good electrode?
it is unreactive but conducts electricity
with a non-metal half-call how do you work out which way the electrons are going to move?
the oxidation reaction always gives electrons to the reduction reaction
what does a salt bridge (ion bridge) do?
it links two half cells and completes the circuit by allowing ions to pass across the bridge
what is an electrolyte?
a solution containing ions which can conduct electricity?
how can the most simple cell be made?
put 2 different metals in an electrolyte
what is a half-cell?
a metal in a solution of its own ions
do all half-cells contain a metal?
no- graphite may be used
which way do electrons travel in an electrochemical cell?
from the metal higher up in the electrochemical series to the one lower down
how does the voltage in electrochemical calls vary?
the further apart the metals are in the electrochemical series, the greater the voltage will be
give an example of a polymer?
plastics, starch, rubber, etc.
what are polymers?
long chain molecules made up by joining together lots of smaller molecules called monomers
what is a monomer?
a small molecule with a functional group such as C=C that will allow it to become part pf a long chain
what are addition polymers?
polymers made by joining unsaturated molecules together in an addition reaction
how are addition polymers named?
use the prefix ‘poly’ in front of the monomer name
e.g. propane = polypropane
what is the process of making polymers called?
polymerisation
what are repeating groups?
a small section of polymer that is repeated over and over to make the complete chain/
which elements do the compounds in fertilisation?
Nitrogen, potassium and phosphorous (NPK)
what do fertilisers do?
put elements essential for plant growth back into the soil
which compounds are commonly used to make nitrogen salts that are used as fertiliser?
ammonia and nitric acid
what is ammonia?
a strong smelling, colourless, soluble gas
it dissolves to make an alkaline solution
complete the equation
ammonia solution + acid =
ammonium salt + water
what process is used to make ammonia?
haber process
describe the haber process
nitrogen and hydrogen are reacted to make ammonia using an iron catalyst and a moderate heat
why is a moderate temperature used in the haber process?
at low temperatures the reaction is too slow. increasing the temperature increases the rate of reaction but also makes the backward reaction more dominant
so they compromise and go between the 2 extremes
what process is used to make nitic acid?
the Ostwald process
describe the Ostwald process
ammonia is reacted with oxygen and water to produce nitric acid.a platinum catalyst is used
what is a radioisotope?
an isotope with an unstable nuclei which will change to become more stable by giving out radiation
what is radioactivity?
particles and rays given out by unstable isotopes
what are three types of radiation?
- alpha
- beta
- gamma
what is alpha radiation? (mass, charge and ability to penetrate)
a positively charged helium ion.
(mass=4, charge=+2 and is stopped by a sheet of paper
what is beta radiation? (mass, charge and ability to penetrate)
a high energy electron
mass=0 (almost), charge=-1 and is stopped by 2mm of aluminium
what is gamma radiation? (mass, charge and ability to penetrate)
it is not a particle, it is an electromagnetic ray
mass=no mass, charge=no charge and is stopped by thick lead or concrete
what is it meant by the term half-life?
the time it takes for a half of the nuclei of a radioisotope to decay
how does carbon dating work?
carbon-14 is an unstable radioisotope but gets into living things as carbon dioxide. as soon as somethings dies the amount carbon-14 decreases. the amount of radioactivity therefore gives its age
how can you spend up the half life of a nuclear reaction?
you can’t
they are not chemical reactions so are unaffected by chemical or physical conditions
what can radioisotopes be used for?
to detect and treat cancer
to detect leaks in pipes
what can gamma rays be used for?
- to sterilise surgical instruments
- to kill bacteria on food so it keeps longer
what technique can be used to detect metals present in compounds?
flame testing
what are standard solutions?
solutions of very accurately known concentrations
what is a precipitate?
a solid formed from 2 solutions
what are concordant titration results?
results that are within 0.2cm^3 of each other
