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IGCSE Chemistry > theory > Flashcards

theory Flashcards

1
Q

5 properties of solids

A
  • fixed volume and shape
  • high density
  • atoms vibrate in position (but cant change location
  • particles are packed very closely together in a fixed and regular pattern
  • unable to be compressed
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2
Q

5 properties of liquids

A
  • fixed volume but adopt shape of the container
  • less dense than solids more dense than gases
  • particles move and slide past each other (flow freely) (still touching)
  • unable to be compressed
  • randomly arranged
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3
Q

5 properties of gases

A
  • no fixed volume and adopt shape of container
  • low density
  • gas can be compressed into a smaller volume
  • particles move randomly and far apart around 500m/2 in all directions
  • collide with each other and sides of container (creating pressure)
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4
Q

what is boiling

A

when liquid turns into gas

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5
Q

what is melting

A

when a solid turns into liquid

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5
Q
A
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6
Q

what is evaporating

A

liquid turns into GAS

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7
Q

what is freezing

A

when liquid turns to solid

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8
Q

what is condensing

A

when a gas turns into a liquid

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9
Q

how does pressure and temp affect volume of gas

A

temp = directly proportional leads to more pressure so pressure is directly proportional to temp

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10
Q

what is diffusion

A

the movement of particles from a region of higher concentration to a region of lower region of concentration due to the random motion of particles (no energy required) until equilibrium is reached

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11
Q

what is the mass of a gas at 1atm and room temp

A

24dm^3

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12
Q

how does molecular mass affect diffusion of gas

A

more molecular mass = slower diffusion
particle is heavier therefore slower

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13
Q

what is an element

A

a pure substance made of atoms that all contain the same number of protons and cannot be split into anything simpler

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14
Q

what is a compound

A

a pure substance made up of two or more elements chemically combined (cannot be separated into their elements by physical means)

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15
Q

what is a mixture

A

a combination of two or more substances (elements/compounds etc) that are not chemically combined. can be seperated by physical methods such as filtration of evaporation

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16
Q

describe the structure of the atom

A

central nucleus containing neutrons and protons surrounded by electrons in shells

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17
Q

relative charge of proton

A

+1

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18
Q

relative charge of neutron

A

0 or nil

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19
Q

relative charges of an electron

A

-1

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20
Q

relative mass of proton

A

1

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21
Q

relative mass of a neutron

A

1

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22
Q

relative mass of an electron

A

1/1840

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23
Q

what is proton number/atomic number

A

number of protons in the nucleus of an atom

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24
Q

what is mass number/nucleon number

A

total number of protons and neutrons in the nucleus of an atom

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25
Q

what does the group tell us

A

the number of electrons in valence shell

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26
Q

what does the period tell us

A

how many shells of electrons

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27
Q

what do group VIII have?

A

full valence shell

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28
Q

what is an isotope?

A

different atoms of the same element that have the same number of protons but different numbers of neutrons

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29
Q

why do isotopes of the same element have the same chemical properties

A

they have the same number of electrons and therefore have the same electronic configuration

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30
Q

what is a positive ion called

A

cation

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31
Q

what is a negative ion called

A

anion

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32
Q

what is an ionic bond

A

strong electrostatic attraction between oppositely charged ions

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33
Q

what is a giant lattice of ionic compounds

A

regular arrangement of alternating arrangement of alternating positive and negative ions

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34
Q

what type of elements can form ionic bonds

A

non metallic and metallic

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35
Q

what are 2 properties of ionic compounds

A
  • high mp/bp
  • good electrical conductivity when aqueous or molten but poor when solid (ions are free to move around)
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36
Q

what is a covalent bond

A

formed when a pair of electrons is shared between two atoms leading to the noble gass electronic configurations

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37
Q

what properties do simple covalent structures have

A
  • low mp/bp (in terms of weak intermolecular forces)
  • poor electrical conductivity
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38
Q

2 giant covalent structures

A
  • graphite
  • diamond
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39
Q

2 uses of graphite

A
  • lubricant
  • electrode
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40
Q

use of diamond

A
  • cutting tools
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41
Q

why graphite can conduct electricity

A

only bonds with other carbons 3 times - leaving one delocalized electron which becomes shed to create sea of electrons

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42
Q

what is the structure of diamond

A

bonds with 4 carbons - forms tetrahedron

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43
Q

describe intermolecular bonds between simple covalent moelecules

A

weak intermolecular forces between neighbouring molecules. low mp and bp because of the weak bonds between molecules. the intramolecular forces of attraction in covalently bonded atoms

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44
Q

what type of attraction is in covalent bonded molecules

A

intermolecular between molecules

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45
Q

properties of giant covalent

A
  • ## high mp/bp
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46
Q

what is silicon (iv) oxide

A

known as silicon dioxide/silica. SiO2 is a macromolecular compound which occurs as sand and quartz. each oxygen atom forms covalent bonds with 2 silicon atoms and each silicon atom forms covalent bonds with 4 oxygen atoms (tetrahedron is formed)

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47
Q

how does diamond compared to silicon (iv) oxide

A
  • SiO2 has lots of strong covalent bonds (no intermolecular forces so similar properties to diamond)
  • hard
  • high bp
  • insoluble in water
  • does not conduct electricity
  • cheap (available naturally): used to make sandpaper, line inside of furnaces
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48
Q

what is metallic bonding

A

electrostatic attraction between positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons

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49
Q

properties of metallic bonding

A
  • good electrical conductivity
  • malleable/ductile
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50
Q

what is the empirical formula

A

the simplest whole number ration of the different atoms/ions in a compound

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51
Q

what is the mole, mol

A

the unit amount of substance. one mole contains 6.02 x 10^23 particles (atoms, ions, molecules) this is avogadros constant

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52
Q

how to calculate moles

A

mass(g) / molar mass (g/mol)

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53
Q

what is electrolysis

A

decomposition of an ionic compound, when in molten or aqueous solution, by the passage of an electric current

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54
Q

what is the anode

A

positive electrode

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55
Q

what is the cathode

A

negative electrode

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56
Q

what is the electrolyte

A

the molten/aqueous substance that undergoes electrolysis

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57
Q

what type of electrodes do we use

A

inert. made of platinum or carbon/graphite

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58
Q

3 signs that a new substance has formed

A
  • effervescence (fizzing)
  • colour change
  • temperature changes
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59
Q

4 factors affecting rates of reaction

A
  • concentration (pressure for gases)
  • surface area of solid reactants
  • temperature of the reaction
  • presence of a catalyst
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60
Q

3 things needed for reaction to occur

A
  • particles must collide
  • must collide with successful orientation
  • collision must have sufficient energy (activation energy)
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61
Q

what is a reversibe reaction

A

product molecules react with each other or decompose to form reactant molecules

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62
Q

what are hydrated salts

A

salts that contain water of crystallisation which affects their molecular shape/colour

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63
Q

what are the 2 examples of hydrated salts

A
  • copper (II) sulfate pentahydrate
  • cobalt (II) chloride hexahydrate
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64
Q

what color is hydrous and anhydrous copper (II) sulfate pentahydrate

A

hydrous: blue crystals
anhydrous: white crystals/powder

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65
Q

exothermic or endothermic from hydrated copper sulfate to anhydrated copper sulfate

A

endothermic

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66
Q

what is molecular formula of copper (II) sulfate

A

CuSO4 , 5H20

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67
Q

what colour is hydrous and anhydrous cobalt (II) chloride

A

hydrous: pink crystals
anhydrous: blue crystals

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68
Q

from hydrated cobalt (II) chloride to anhydrated cobalt (II) chloride whats the color change?

A

pink to blue

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69
Q

is the reaction from hydrated cobalt (II) chloride to anhydrated cobalt exo or endo

A

endothermic

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70
Q

what is the hydration of CoCl2 and CuSO4 chemical tests used for?

A

prescence of water

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71
Q

molecular formula for copper (II) chloride

A

CoCl2 , 6H2O

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72
Q

what is equilibrium

A

the rate of the forward and backwards reaction are equal. can only occur in a closed system. concentration of reactants and products remain constant

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73
Q

what does the haber process do

A

ammonia is manufactured by an exothermic reaction

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74
Q

what is the equation for haber process

A

N2 (g) + 3H2 (g) -> 2NH3 (g)

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75
Q

where is hydrogen obtained from in haber process

A

obtained from methane

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76
Q

where is nitrogen obtained from in haber process

A

obtained from the air

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77
Q

conditions of haver process

A

temp = 450 celcius
pressure = 200 atm
catalyst = iron

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78
Q

steps of haber process

A
  • hydrogen and nitrogen pumped into compressor
  • inside compressor gases are compressed to 200atm
  • pressurized gases pumped into tank containing layers of iron catalyst at 450C. some of hydrogen and nitrogen react to form ammonia
  • unreacted H2 and N2 and the ammonia product pass into cooling tank. ammonia liquefied and removed to pressurised storage vessels.
  • unreacted H2 and N2 gases recycled back to system
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79
Q

explain temp used in haber process

A

high temp favour reverse reaction however rate of reaction is faster. compromise between low yield of products but quicker

80
Q

explain pressure used in haver process

A

high pressure favours forward reaction (high yield of products). since high pressure is very dangerous and expensive equipment is required, it is a compromise pressure of lower yield of products being made safely and economically

81
Q

explain catalyst used in haner process

A

Prescence of catalyst does not affect position of equilibrium, but increases the rate at which equilibrium is reached (increases forward and backward reaction by the same amount)

82
Q

what does the contact process do

A

sulfuric acid synthesized by this exothermic reaction

83
Q

what is sulfuric acid used for

A

fertilisers, soap, detergents,

84
Q

Describe the transfer of charge during electrolysis in terms of electrons

A

the movement of electrons in the external circuit. cations gain electrons, and anions lose electrons

85
Q

Describe the transfer of charge during electrolysis in terms of ions

A

ions in the electrolyte carry the charge

86
Q

what is anode

A

positive electrode

87
Q

what is cathode

A

negative electrode

88
Q

what is electrolyte

A

molten/aqueous substance that undergoes electrolysis

89
Q

what is produced at cathode

A

hydrogen or metals

90
Q

what is produced at anode

A

non–metals

91
Q

what are the products of electrolysis of molten lead (II) bromide

A

lead = cathode
bromine = anode

92
Q

what are the products of electrolysis of concentrated aqueous sodium chloride

A

hydrogen = cathode
chlorine = anode

93
Q

what is brine

A

concentrated solution of aqueous sodium chloride

94
Q

what is solution remaining in electrolysis of concentrated aqueous sodium chloride

A

sodium hydroxide

95
Q

what is the rule of what forms at cathode in during electrolysis of aqueous solutions

A

if its less reactive than hydrogen it will form at cathode

96
Q

what is the rule for what forms at the anode during electrolysis of aqueous solutions

A

if a halide ion is present, halogen is formed. if no halide ions are present, then oxygen is formed

97
Q

what products are formed during the electrolysis of dilute sulfuric acid

A

hydrogen = cathode
oxygen = anode

98
Q

dissociation of water in electrolysis of aqueous solutions

A

H2O ⇌ H+ + OH-

99
Q

what happens if in an aqueous solution there are 2 ions of different concentrations

A

the more concentrated ion will tend to get discharged over a more dilute ion

100
Q

what happens if a concentrated halide is being electrolysed, what forms at the anode

101
Q

what happens if a dilute halide is being electrolysed, what forms at the anode

102
Q

half equation for reaction at cathode during electrolysis of copper

A

Cu2+ + 2e– → Cu

103
Q

half equation at anode for hydroxide

A

4OH– ⟶ O2 + 2H2O + 4e–

104
Q

what happens if copper electrodes are used during electrolysis of copper compound

A
  • cathode increases in mass (Cu+2 are reduced at the cathode and form copper atoms)
  • anode decreases in mass (copper atoms oxidised at anode and forms Cu+2)

gain in mass by cathode is same as decrease in mass of anode

105
Q

why are metal objects electroplated

A

improve appearance and resistance to corrosion

106
Q

how are half equations written for positive ions

A

only neutral atom on the right
Li+ + e– → Li

Cu2+ + 2e– → Cu

Al3+ + 3e– → Al

107
Q

halide/halogen half equations

A

If a halogen is formed during electrolysis
- two halide ions will nose 2 electrons to form halogen (halide ions are oxidised)
2X– → X2 + 2e–
only ion on the left

108
Q

hydroxide/oxygen half equation

A

4OH– → O2 + 2H2O + 4e–

109
Q

what does hydrogen-oxygen fuel cell use

A

hydrogen and oxygen to produce electricity with water as the only chemical product

110
Q

what is an exothermic reaction

A

transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings

111
Q

what is an endothermic reaction

A

takes in thermal energy from the surroundings leading
to a decrease in the temperature of the
surroundings

112
Q

what is transfer of thermal energy during a reaction called

A

enthalpy change

113
Q

what is activation energy

A

the minimum
energy that colliding particles must have to react

114
Q

is bond breaking endo or exo

A

endothermic

115
Q

is bond making exo or endo

A

exothermic

116
Q

how to test for prescence of water

A

use anhydrous cobalt (II) chloride/ anhydrous copper (II) sulfate

117
Q

how to test for purity

A

pure substance boil and melt at a fixed point

118
Q

what is distilled water?

A

water that has been heated to form a vapour and condensed back to a liquid (contains very few impurities)

119
Q

why is tap water typically not used

A

more impurities than distilled (interfere with chemical reactions)

120
Q

what is a physical property

A

characteristic of a substance that can be observed/measured without changing identity of the substance

121
Q

7 physical properties

A
  • color
  • hardeness
    -malleability
  • solubility
  • conductivity
  • density
    -mp/bp
122
Q

what are chemical properties

A

potential to undergo chemical change or reaction by virtue of its compositions (electrons and bonds that are present give matter potential for chemical change)

123
Q

4 things to mention in collision theory

A
  • number of particles per unit volume
  • frequency of collisions between particles
  • Ek of particles
  • activation energy
124
Q

what does a catalyst do

A

increases rate of reaction and is unchanged at the end of a reaction (decreases activation energy Ea of a reaction

125
Q

practical methods for investigating the rate of reaction

A
  • change in mass of reactant/product
  • formation of gas
126
Q

sources of sulfur dioxide

A
  • burning sulfur
  • roasting sulfide ores
  • oxygen
127
Q

what catalyst does contact process use

A

vanadium oxide

128
Q

what is redox reactions

A

involves simultaneous oxidation and reduction

129
Q

define oxidation

A
  • gain oxygen
  • loss of electrons
  • increase in oxidation
130
Q

define reduction

A
  • loss of oxygen
  • gain of electrons
  • decrease in oxidation number
131
Q

how identify redox reactions

A

gain and loss of electrons

132
Q

oxidation number of elements in umcombined state is

133
Q

what is oxidation number of a monatomic ion

A

same charge on the ion

134
Q

sum of oxidation numbers in a compound

135
Q

sum of oxidation numbers in an ion

A

equal to the charge on the ion

136
Q

what is potassium manganate (VII)

A

oxidising agent often used to test for the presence of reducing agents

137
Q

what happens acidified potassium manganate is added to a reducing agent

A

purple to colourless

138
Q

what is potassium iodide (KI)

A

reducing agent often used to test for the presence of oxidising agents

139
Q

what haappens when KI is added to acidified solution of oxidising agent

A

solution turns red brown due to the formation of iodine

140
Q

what is an oxidising agent

A

substance that oxidises another substance and is itself reduced

141
Q

what a reducing agent

A

substance that reduces another substance and is itself oxidised

142
Q

3 indicators

A

-litmus
- thymolphthalein
- methyl orange

143
Q

color of methyl orange in acid and alkali

A

acid = red
alkali = yellow

144
Q

color of thymolphthalein in acid and alkali

A

acid= colourless
alkali = blue

145
Q

what are bases

A

oxides/hydroxides of metals

146
Q

what are alkalis

A

soluble bases

147
Q

define acid

A

proton donors (when added to water they form H+ ions, and presence of H+ ions makes a solution acidic)

148
Q

what type of elements will react with dilute acids

A

metals above hydrogen in reactivity series

149
Q

what is a strong acid

A

an acid that is completely dissociated in aqueous solution a

150
Q

what is a weak acid

A

an acid that is partially dissociated in aq solution

151
Q

what happens when alkalis are added to water

A

form negative hydroxide ions

152
Q

what makes an aq solution alkaline

A

presence of OH- ions

153
Q

what happens to ammonium salts when warmed with an alkali

A

undergo decomposition

154
Q

what can displace ammonia

155
Q

what is produced when alkali and ammonia are warmed together

A

salt, water and ammonia

156
Q

what is pH

A

concentration of H+ ions per dm3 of solution

157
Q

what 2 elements can form amphoteric oxides

A

aluminium and zinc

158
Q

what is an amphoteric oxide

A

oxides that react with acids and bases to produce salt and water

159
Q

what 2 oxides are acidic

A

SO2 and CO2 because they are non metal oxides

160
Q

what are basic oxides

A

CuO and CaO because they are both metal oxides

161
Q

what is a salt

A

a compound that is formed when the hydrogen atom in an acid is replaced by a metal

162
Q

2 methods on how to prepare a soluble salt

A
  • adding acid to a solid metal, insoluble base or insoluble carbonate
  • reacting a dilute acid and alkali (alkali by titration)
163
Q

how to prepare soluble salt by adding acid to solid metal or insoluble base/carbonate

A
  • warm acid (increases speed of reaction)
  • add excess reactant and stir
  • filter mixture
  • transfer to evaporating basin
  • heat using bunsen burner
  • leave to cool until crystallisation point
  • wash crystals with distilled water
  • dry crystals on filter paper
164
Q

how to prepare soluble salt by titration

A
  • place known volume of alkali into conical flask using a pipette
  • add indicator (e.g. thymolphthalein)
  • add acid using burette until end point has reached
  • record volume of acid added
  • repeat without indicator
  • transfer to evaporating basin
  • heat with bunsen burner
  • leave till crystallisation point
  • wash crystals with distilled water
  • dry crystals on filter paper
165
Q

how to prepare insoluble salt by precipitation

A
  • mix 2 soluble salts
  • filter to remove precipitate
  • wash precipitate with distilled water
  • leave to dry
166
Q

what is a hydrated substance

A

substance that is chemically combined with water

167
Q

what is a anhydrous substance

A

substance containing no water

168
Q

what is water of crystallisation

A

water molecules present in hydrated crystals

169
Q

what is the periodic table

A

arrangement of elements in periods and groups and in order of increasing atomic number

170
Q

general trends of group I alkali metals

A
  • relatively soft
  • decreasing melting point
  • increasing density
  • increasing reactivity
171
Q

describe general trends of group VII

A
  • increasing density
  • decreasing reactivity
172
Q

state appearance of chlorine at rtp

A

pale yellow-green gas

173
Q

state appearance of bromine at atp

A

red brown liquid

174
Q

state appearance of iodine at rtp

A

a grey-black solid

175
Q

what color is solid iodine

A

dark grey-black

176
Q

what color is aqueous iodine

177
Q

what color is iodine vapour

178
Q

what is a group VII displacement reaction

A

a halogen displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide

179
Q

color of chlorine in aq solution

A

very pale green

180
Q

color of bromine in aq solution

A

orange but will turn yellow when diluted

181
Q

5 properties of transition metals

A
  • high densities
  • high mp
  • form coloured compounds
  • often act as catalysts
  • variable oxidation numbers
182
Q

describe group VIII noble gases

A

unreactive, monatomic gases, due to having a full valence shell. electronic configuration is extremely stable so these elements are unreactive and inert

183
Q

reaction of metal and cold water

A

metal + water -> metal hydroxide + hydrogen

184
Q

reaction of metals that react with steam

A

metal + water _> metal oxide + hydrogen

185
Q

reaction of metal and oxygen

A

metal + oxygen -> metal oxide

186
Q

3 uses of aluminium due to physical property

A
  • manufacture of aircraft due to low density
  • overhead electrical cables due to low density and electrical conductivity
  • food containers due to resistance to corrosion
187
Q

what is an alloy

A

mixture of metal with other elements

188
Q

what is brass an alloy of

A

mixture of copper and zinc

189
Q

what is stainless steel an alloy of

A

mixture of iron, chromium, nickel and carbon

190
Q

why do we alloy

A

harder, stronger than pure metals and are more useful

191
Q

why are alloys harder and stronger than pure metals

A

because different sized atoms in alloys mean layers can no longer slide over each other

192
Q

why is stainless steel used in cutlery

A

hardness and resistance to rusting

193
Q

use of copper due to physical property

A
  • electrical wiring due to good conductivity and ductility
194
Q

what happens to the top of the reactivity series when reacted with cold water (potassium, sodium and calcium)

A

reacts violently

195
Q

describe reaction of magnesium with water

A

slow reaction (reacts with steam)

196
Q

describe the relative reactivaties of metals

A

tendency to form positive ions by displacement reactions

197
Q

explain aluminiums unapparent unreactivity

A

oxide layer - prevents reaction with water and dilute acids

IGCSE Chemistry (12 decks)

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