Unit 3

Question 1

why do metals conduct electricity?

Answer 1

because the outer electrons are delocalised (free to move)

Question 2

what is a metallic bond?

Answer 2

the electrostatic force of attraction between positively charges ions and their delocalised electrons

Question 3

complete the equation

metal + oxygen =

Answer 3

metal oxide

Question 4

complete the equation

metal + water =

Answer 4

metal hydroxide + hydrogen

Question 5

complete the equation

metal + acid =

Answer 5

salt + hydrogen

Question 6

how can metals be used to make soluble salts?

Answer 6

excess metal is added to the correct acid
mixture is filtered to remove unreacted metal
filtrate is evaporated to dryness

Question 7

what is reduction?

Answer 7

gain of electrons

Question 8

what is oxidation?

Answer 8

loss of electrons

Question 9

what is a redox reaction?

Answer 9

when both oxidation and reduction take place at the same time

Question 10

when a metal is extracted from its ore is a metal being oxidised or reduced?

Answer 10

reduced

Question 11

what is an ore?

Answer 11

a compound containing useful amounts of metal ions

Question 12

what happens to a metal ion when they are being extracted from metal ores?

Answer 12

they gain electrons to change from ions to atoms

Question 13

how are very reactive metals obtained from their ores?

Answer 13

electrolysis

Question 14

how can very unreactive metals be obtained from their ores?

Answer 14

by heat alone

Question 15

how are most metals extracted from their ores?

Answer 15

heating with carbon or carbon monoxide

Question 16

what is electrolysis?

Answer 16

the breaking of an ion compound into its elements using electricity

Question 17

why must a D.C. supply be used for electrolysis?

Answer 17

to allow the elements to build up at the electrodes for identification

Question 18

what happens at the electrodes during electrolysis?

Answer 18

positive ions gain electrons at the negative electrode

negative ions lose electrons at the positive electrodes

Question 19

how do you make a current flow using two different metals in a solution of their own ions? (2 half cells)

Answer 19

connect the metals with a wire
connect the solutions with a salt bridge
the electrons will flow along the wire

Question 20

why does graphite make a good electrode?

Answer 20

it is unreactive but conducts electricity

Question 21

with a non-metal half-call how do you work out which way the electrons are going to move?

Answer 21

the oxidation reaction always gives electrons to the reduction reaction

Question 22

what does a salt bridge (ion bridge) do?

Answer 22

it links two half cells and completes the circuit by allowing ions to pass across the bridge

Question 23

what is an electrolyte?

Answer 23

a solution containing ions which can conduct electricity?

Question 24

how can the most simple cell be made?

Answer 24

put 2 different metals in an electrolyte

Question 25

what is a half-cell?

Answer 25

a metal in a solution of its own ions

Question 26

do all half-cells contain a metal?

Answer 26

no- graphite may be used

Question 27

which way do electrons travel in an electrochemical cell?

Answer 27

from the metal higher up in the electrochemical series to the one lower down

Question 28

how does the voltage in electrochemical calls vary?

Answer 28

the further apart the metals are in the electrochemical series, the greater the voltage will be

Question 29

give an example of a polymer?

Answer 29

plastics, starch, rubber, etc.

Question 30

what are polymers?

Answer 30

long chain molecules made up by joining together lots of smaller molecules called monomers

Question 31

what is a monomer?

Answer 31

a small molecule with a functional group such as C=C that will allow it to become part pf a long chain

Question 32

what are addition polymers?

Answer 32

polymers made by joining unsaturated molecules together in an addition reaction

Question 33

how are addition polymers named?

Answer 33

use the prefix 'poly' in front of the monomer name | e.g. propane = polypropane

Question 34

what is the process of making polymers called?

Answer 34

polymerisation

Question 35

what are repeating groups?

Answer 35

a small section of polymer that is repeated over and over to make the complete chain/

Question 36

which elements do the compounds in fertilisation?

Answer 36

Nitrogen, potassium and phosphorous (NPK)

Question 37

what do fertilisers do?

Answer 37

put elements essential for plant growth back into the soil

Question 38

which compounds are commonly used to make nitrogen salts that are used as fertiliser?

Answer 38

ammonia and nitric acid

Question 39

what is ammonia?

Answer 39

a strong smelling, colourless, soluble gas | it dissolves to make an alkaline solution

Question 40

complete the equation | ammonia solution + acid =

Answer 40

ammonium salt + water

Question 41

what process is used to make ammonia?

Answer 41

haber process

Question 42

describe the haber process

Answer 42

nitrogen and hydrogen are reacted to make ammonia using an iron catalyst and a moderate heat

Question 43

why is a moderate temperature used in the haber process?

Answer 43

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

Question 44

what process is used to make nitic acid?

Answer 44

the Ostwald process

Question 45

describe the Ostwald process

Answer 45

ammonia is reacted with oxygen and water to produce nitric acid.a platinum catalyst is used

Question 46

what is a radioisotope?

Answer 46

an isotope with an unstable nuclei which will change to become more stable by giving out radiation

Question 47

what is radioactivity?

Answer 47

particles and rays given out by unstable isotopes

Question 48

what are three types of radiation?

Answer 48

- alpha - beta - gamma

Question 49

what is alpha radiation? (mass, charge and ability to penetrate)

Answer 49

a positively charged helium ion. | (mass=4, charge=+2 and is stopped by a sheet of paper

Question 50

what is beta radiation? (mass, charge and ability to penetrate)

Answer 50

a high energy electron | mass=0 (almost), charge=-1 and is stopped by 2mm of aluminium

Question 51

what is gamma radiation? (mass, charge and ability to penetrate)

Answer 51

it is not a particle, it is an electromagnetic ray | mass=no mass, charge=no charge and is stopped by thick lead or concrete

Question 52

what is it meant by the term half-life?

Answer 52

the time it takes for a half of the nuclei of a radioisotope to decay

Question 53

how does carbon dating work?

Answer 53

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

Question 54

how can you spend up the half life of a nuclear reaction?

Answer 54

you can't | they are not chemical reactions so are unaffected by chemical or physical conditions

Question 55

what can radioisotopes be used for?

Answer 55

to detect and treat cancer | to detect leaks in pipes

Question 56

what can gamma rays be used for?

Answer 56

- to sterilise surgical instruments | - to kill bacteria on food so it keeps longer

Question 57

what technique can be used to detect metals present in compounds?

Answer 57

flame testing

Question 58

what are standard solutions?

Answer 58

solutions of very accurately known concentrations

Question 59

what is a precipitate?

Answer 59

a solid formed from 2 solutions

Question 60

what are concordant titration results?

Answer 60

results that are within 0.2cm^3 of each other