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chemistry qma revision 2018 Flashcards

1
Q

definition of an atom

A

smallest neutral part of an element that can take part in chemical reactions

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2
Q

definition of an element

A

made up of one type of atom, substances that cannot be split up into simpler substances

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3
Q

definition of a compound

A

different elements/different atoms that are chemically combined together (by chemical bonds)

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4
Q

definition of a molecule

A

two or more elements joined together (by covalent bonds)

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5
Q

definition of a mixture

A

two or more substances/elements/compounds that are not chemically combined. They are mixed together, they can usually be separated by physical methods

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6
Q

definition of a chemical change

A

when a reaction occurs between two or more substances to create a new chemical

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7
Q

definition of a physical change

A

a change where no new substances are formed

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8
Q

definition of a nucleus

A

the very small and dense central part of an atom

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9
Q

definition of an electron

A

a tiny particle with a negative charge

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10
Q

definition of a proton

A

a tiny positively charged particle found inside the nucleus of an atom

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11
Q

definition of a neutron

A

a dense particle found in the nucleus, it carries no charge

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12
Q

definition of an atomic number

A

the number of protons inside an atom

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13
Q

definition of mass number

A

the number of protons plus neutrons in the nucleus of an atom

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14
Q

definition of isotopes

A

atoms of the same element, which have the same number of protons (and electrons) but different number of neutrons

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15
Q

what do electrons orbit the nucleus in

A

energy levels (shells)

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16
Q

definition of chromatography

A

used to separate mixtures of coloured compounds. They are separated based on their density, - the lower the density, the further it travels up the paper

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17
Q

definition of magnetism

A

used to separate magnetic metals from non-magnetic substances

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18
Q

definition of crystallisation

A

used to separate dissolved salts from their solvent. Heating the solution evaporates the solvent leaving the salt crystals

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19
Q

definition of separating funnel

A

used to separate immiscible liquids. Opening the tap on the funnel allows the less dense bottom layer to flow through. The tap can be closed when the top layer reaches the bottom

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20
Q

definition of filtration

A

used to separate insoluble solids from liquids. The solid residue is left in the filter paper as it cannot pass through and the liquid filtrate passes through

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21
Q

definition of simple distillation

A

used to separate miscible liquids based on their different boiling points. The liquid with the lower boiling point boils first and the gas passes down the condenser, cools and condenses again.

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22
Q

definition of fractional distillation

A

used to separate miscible liquids based on their different boiling points. The liquids will evaporate and rise up the column. The liquid with the highest boiling point will condense on the beads and drip back down whilst the liquid with the lowest boiling point will rise and pass into the condenser where it will cool and condense

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23
Q

why have ideas about atoms changed over time

A

scientists have gathered new evidence from experiments and new technology has advanced

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24
Q

when did Democritus propose his ideas about atoms

A

400bc

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25
Q

what did Democritus say

A

he was the first to have the idea that everything was made of particles - he called them atoms

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26
Q

when did John Dalton propose his ideas about atoms

A

1803

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27
Q

what did John Dalton say

A

he described atoms like billiard balls and said that atoms of the same element were identical. He also thought that these atoms could not be split.

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28
Q

when did JJ Thompson propose his ideas about atoms

A

1897

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29
Q

what did JJ Thompson say

A

he discovered the electron by passing high voltage electricity through gases. He proposed the “plum pudding” model of the atom - a ball of positive charge with the negative electrons embedded in it

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30
Q

when did Rutherford and Marsden propose their ideas about atoms

A

1909

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31
Q

what did Rutherford and Marsden say

A
  • conducted the gold leaf experiment by firing positive alpha particles at a thin gold foil
  • expected the particles to pass straight through based on “plum pudding” model
  • instead some bounced back and some deflected in other directions
  • this gave rise to the “nuclear” model, a positive dense nucleus in the centre surrounded by lighter negatively charged electrons
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32
Q

when did Neils Bohr propose his ideas about atoms

A

1913

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33
Q

what did Neils Bohr say

A

agreed with the nuclear model and suggested that electrons orbited at specific distances, otherwise known as “shells”

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34
Q

when did Ernest Rutherford propose his ideas about atoms

A

1920

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35
Q

what did Ernest Rutherford say

A

suggested the name proton for a hydrogen nucleus

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36
Q

when did James Chadwick propose his ideas about atoms

A

1932

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37
Q

what did James Chadwick say

A

that there must be another particle in the nucleus. Proved the existence of the neutron and measured its mass

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38
Q

differences between plum-pudding and nuclear model

A

plum-pudding:

  • single ball of positive charge with electrons in random positions
  • has no nucleus

nuclear model:

  • positive charge in the centre/nucleus
  • electrons in fixed positions arranged in shells
  • has a nucleus
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39
Q

comparison 1 between plum-pudding and nuclear

A

in plum-pudding, the protons are not sub-atomic particles (are a ball of positive charge), whereas in nuclear the protons are in the nucleus

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40
Q

comparison 2 between plum-pudding and nuclear

A

in plum-pudding, the electrons are embedded in the ball of positive charge whereas in the nuclear model they are in shells

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41
Q

comparison 3 between plum-pudding and nuclear

A

plum-pudding has no neutrons whereas the nuclear model has them in the nucleus

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42
Q

comparison 4 between plum-pudding and nuclear

A

plum-pudding has its mass spread throughout the atom whereas the nuclear model has it concentrated in the nucleus

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43
Q

what is the radius of an atom

A

0.1nm

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44
Q

what is ratio of a nucleus to an atom

A

1:10,000

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45
Q

how to convert nm to m

A

x 10^-9

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46
Q

how to convert m to nm

A

/ 10^-9

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47
Q

what is relative atomic mass

A

the average mass of the atoms of an element compared with an atom of carbon-12. The average mass takes into account the proportion of the isotopes of the element

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48
Q

how to calculate relative atomic mass

A

(total mass of all atoms of that element) / (total number of that element

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49
Q

4 rules of electronic structure

A
  • always fill the shells from the centre
  • the first shell can hold 2 electrons
  • the second shell can hold 8 electrons
  • the third shell can hold 8 electrons before the fourth starts to fill up
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50
Q

what is the group number equal to

A

number of electrons in outer shell

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51
Q

what is the period number equal to

A

number of shells

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52
Q

who was the first to develop the periodic table

A

Dobereiner

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53
Q

what did Dobereiner say

A

notice groups of elements so put forward “law of triads”. Examples: lithium, sodium, potassium & chlorine, bromine, iodine

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54
Q

who was the second to develop the periodic table

A

Newlands

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55
Q

What did Newlands say

A
  • the first to order elements by atomic mass and noticed patterns of properties every 8 elements
  • proposed the law of octaves
  • ideas were rejected as the order went wrong after calcium
  • e.g. unreactive copper in same group as lithium, sodium and potassium
56
Q

who was the third to develop the periodic table

A

mendeleev

57
Q

what did Mendeleev say

A
  • ordered elements by atomic mass as well
  • left gaps for elements that hadn’t been discovered
  • swapped the order of some elements so that some properties fit the pattern
  • mendeleev had no knowledge of protons electrons or neutrons but we now know he put them in atomic number
  • excluded noble gases as they hadn’t been discovered
58
Q

difference in boiling points between metals and non-metals

A

metals have high melting and boiling points whereas non-metals don’t

59
Q

difference in densities between metals and non-metals

A

metals have a high density whereas non-metals don’t

60
Q

difference in conductivity between metals and non-metals

A

metals are good thermal and electricity conductors whereas non-metals aren’t (except graphite)

61
Q

difference in shine between metals and non-metals

A

metals are shiny when polished whereas non-metals are dull

62
Q

difference in reactions between metals and non-metals

A

metals react to form negative ions and ionic compound whereas non-metals react to form molecules

63
Q

difference in oxides between metals and non-metals

A

metals have basic oxides whereas non-metals have acidic oxides

64
Q

is there a reaction between metals and non-metals?

A

no

65
Q

difference in shape between metals and non-metals

A

metals are malleable (hammered in shape) whereas non-metals are brittle when solids

66
Q

what group are noble gases in

A

0

67
Q

how reactive are noble gases and why

A

unreactive as they have a full outer shell of electrons so they don’t want to lose or gain any

68
Q

what happens to density of noble gases when you go down the group

A

it increases

69
Q

what happens to boiling point of noble gases when you go down the group

A

increases as the atoms get bigger and there are more weak forces of attraction so more energy is required to break them apart

70
Q

what group are alkali metals in

A

1

71
Q

how hard are alkali metals

A

they are soft and can be cut with a knife

72
Q

what is the melting point of alkali metals

A

have a low melting point, much lower than transition metals

73
Q

do alkali metals conduct electricity

A

yes

74
Q

how dense are alkali metals

A

some are not very dense and will float on water

75
Q

what are the alkali metals’ reactions to water

A

lithium - fizzes and floats
sodium - fizzes floats and sometimes a yellow flame is seen
potassium - fizzes floats melts and burns with a lilac flame

76
Q

metal + water –>

2Li + 2H2O –>

A

metal hydroxide + hydrogen

2LiOH + H^2

77
Q

metal + oxygen –>

4Li + O2 –>

A

metal oxide

2Li2O

78
Q

metal + chlorine –>

2Li + Cl2 –>

A

metal chloride

2LiCl

79
Q

name the stages for alkali metals reactivity

A
  • get more reactive as you go down
  • have one electron in outer shell so need to lose one to have the same electronic structure as noble gas
  • alkali metals further down have less attraction on outer electron, means more shielding
  • outer electrons of alkali metals further down are further away from attractive force of nucleus
  • the outer electron is more easily lost as there are more outer shells and they are further away from attractive force of nucleus
80
Q

what group are halogens in

A

7

81
Q

what is fluorine

A

a pale yellow gas

82
Q

what is chlorine

A

a pale green gas

83
Q

what is bromine

A

a dark brown liquid

84
Q

what is iodine

A

a grey solid (with purple vapours)

85
Q

how do halogens exist as

A

diatonic molecules which means they go round in pairs e.g. F2, Cl2

86
Q

halogen + hydrogen –>

Cl2 + H2 –>

A

hydrogen halide

2HCl

87
Q

halogen + metal –>

Cl2 + “Na

A

metal halide

2NaCl

88
Q

how do displacement reactions work

A

a more reactive halogen displaces a less reactive halogen, a colour change can be seen

89
Q

example of a word displacement reaction

A

chlorine + sodium bromide –> sodium chloride + bromine

90
Q

example of a symbol displacement reaction

A

Cl2 + 2NaBr –> 2NaCl + Br2

91
Q

name the stages for halogens reactivity

A
  • halogens get less reactive as you go down the group
  • have seven electrons in outer shell to have electronic structure of noble gas
  • halogens further down have more shells so there is less attraction for incoming electron, means more shielding
  • outer electrons of halogens further down the group are further away from attraction of nucleus
  • an electron is less easily gained because there are more shells and less attraction of nucleus
  • the harder it is for an atom to gain an electron, the less reactive it is
92
Q

explain the reactivity of transition metals

A

not as reactive as alkali metals but still react with oxygen and chlorine, just more slowly

93
Q

what can transition metals act as

A

catalysts

94
Q

what type of compound do transition metals form compared to alkali metals

A

form coloured compounds whereas alkali metals form white compounds

95
Q

what do transition and alkali metals have in common

A
  • good conductors of heat
  • good conductors of electricity
  • shiny
96
Q

what do transition metals react to form compared to alkali metals

A

ions with different charges whereas alkali metals form ions with a +1 charge

97
Q

definition of collission theory

A

an explanation of chemical reactions in terms of reacting particles colliding with sufficient energy for a reaction to take place

98
Q

definition of activation energy

A

the minimum energy that particles must collide with for a reaction to take place

99
Q

definition of exothermic

A

a reaction that transfers to the surroundings

100
Q

definition of endothermic

A

a reaction that takes in energy from the surroundings

101
Q

definition of reversible reaction

A

a reaction in which the products can re-form the rectants

102
Q

definition of hydrated

A

a substance that contains water in its crystals

103
Q

definition of anhydrous

A

a substance that does not contain water

104
Q

definition of equilibrium

A

the point in a reversible reaction where the forward and reverse reaction take place at the same rate. the amount of substances remain constant, only happens in a closed system

105
Q

definition of Le Chatelier’s principle

A

when a change in conditions happens in equilibrium, position of equilibrium shifts to cancel out the change

106
Q

equation 1 to calculate the mean rate of reaction

A

quantity of reactant used / time taken

107
Q

equation 2 to calculate the mean rate of reaction

A

quantity of product formed / time taken

108
Q

how can quantity of reactant or product be measured

A

in grams, cm^3 or moles

109
Q

units for time taken in rates of reaction

A

g/s, cm^3/s, mol/s

110
Q

how can you calculate the rate of reaction from a graph

A

drawing a tangent and working out the change in product divided by the change in time

111
Q

what affects the rate of reaction

A
  • concentration of reactants in solution
  • pressure (when gases are reacting)
  • surface area of solid reactants
  • temperature
  • catalyst
112
Q

when will a reaction occur

A

when particles collide with sufficient energy

113
Q

what is the minimum amount of energy particles need to react

A

activation energy

114
Q

what will happen as the frequency of successful collisions increases

A

the rate of reaction will icnrease

115
Q

how does increasing concentration affect rate of reaction

A

more particles means particles are closer together so the frequency of collisions increases so the rate of reaction increases

116
Q

how does increasing pressure affect rate of reaction

A

more particles are closer together so the frequency of successful collisions increases so the rate of reaction increases

117
Q

how does increasing the surface area of a solid reactant affect rate of reaction

A

more surface available for the reactant in solution to collide with so the frequency of successful collisions increases so the rate of reaction increases

118
Q

how does increasing the temperature affect rate of reaction

A

the particles have more energy so they collide more energetically, so the frequency of successful collisions increases so the rate of reaction increases

119
Q

4 properties of catalysts

A
  • speed up the rate of reaction
  • are not used up in the reaction
  • different catalysts are needed for different reactions
  • enzymes are biological catalysts
120
Q

how do catalysts increase the rate of reaction

A

providing a different pathway for reaction that has a lower activation energy

121
Q

why are catalysts not included in a chemical reaction

A

they are not used up

122
Q

how is one way you can test for rates of reaction

A

reacting sodium thiosulfate and dilute hydrochloric acid and seeing how long it takes for the “x” to disappear with different concentrations of sodium thiosulfate

123
Q

how can you make the 1st method for testing rates of reaction more accurate

A

using a light sensor to monitor turbidity

124
Q

how is another way you can test for rates of reaction

A
  • filling a measuring cylinder with water and inverting it into a trough with water
  • placing a bung on a conical flask with acid and a magnesium ribbon with the other end underneath the measuring cylinder
  • record the volume of gases at different intervals until reaction has stopped
  • repeat with different concentrations of acid
125
Q

what are reversible reactions

A

where the product can react to produce the original reactants

126
Q

what will the reverse reaction in a reversible reaction be if the forward reaction is exothermic

A

endothermic and will take in the same amount of energy that has been released

127
Q

how can the direction of a reversible reaction be changed

A

by changing the conditions

128
Q

what happens if concentration of reactants increases in equilibrium

A

more products will be formed until equilibrium is reached again

129
Q

what happens if concentration of products decreases in equilibrium

A

more reactants will react to make more products so that equilibrium is reached again

130
Q

what happens if one of reactants or products change concentration in equilibrium

A

concentration of all substances change until equilibrium is reached

131
Q

what happens in an increase in pressure in equilbrium

A

the equilibrium shifts to the side with smaller amounts of molecules (more reactants/products produced)

132
Q

what happens in a decrease in pressure in equilibrium

A

the equilibrium shifts to the side with larger amounts of molecules (more reactants/prodcuts produced)

133
Q

what type of reaction gets warmer and what type gets colder

A

exothermic gets warmer gives out heat

endothermic gets colder takes in heat

134
Q

how can you tell if a reaction is exothermic (gets warmer)

A

the ΔH values are negative

135
Q

what happens in an increase in temperature in equilbrium

A

the equilibrium shifts to the endothermic side

136
Q

what happens in a decrease in temperature in equilbrium

A

the equilibrium shifts to the exothermic side

other (19 decks)

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