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
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
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)
4
Q
what is boiling
A
when liquid turns into gas
5
Q
what is melting
A
when a solid turns into liquid
5
Q
A
6
Q
what is evaporating
A
liquid turns into GAS
7
Q
what is freezing
A
when liquid turns to solid
8
Q
what is condensing
A
when a gas turns into a liquid
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
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
11
Q
what is the mass of a gas at 1atm and room temp
A
24dm^3
12
Q
how does molecular mass affect diffusion of gas
A
more molecular mass = slower diffusion
particle is heavier therefore slower
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
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)
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
16
Q
describe the structure of the atom
A
central nucleus containing neutrons and protons surrounded by electrons in shells
17
Q
relative charge of proton
A
+1
18
Q
relative charge of neutron
A
0 or nil
19
Q
relative charges of an electron
A
-1
20
Q
relative mass of proton
A
1
21
Q
relative mass of a neutron
A
1
22
Q
relative mass of an electron
A
1/1840
23
Q
what is proton number/atomic number
A
number of protons in the nucleus of an atom
24
what is mass number/nucleon number
total number of protons and neutrons in the nucleus of an atom
25
what does the group tell us
the number of electrons in valence shell
26
what does the period tell us
how many shells of electrons
27
what do group VIII have?
full valence shell
28
what is an isotope?
different atoms of the same element that have the same number of protons but different numbers of neutrons
29
why do isotopes of the same element have the same chemical properties
they have the same number of electrons and therefore have the same electronic configuration
30
what is a positive ion called
cation
31
what is a negative ion called
anion
32
what is an ionic bond
strong electrostatic attraction between oppositely charged ions
33
what is a giant lattice of ionic compounds
regular arrangement of alternating arrangement of alternating positive and negative ions
34
what type of elements can form ionic bonds
non metallic and metallic
35
what are 2 properties of ionic compounds
- high mp/bp
- good electrical conductivity when aqueous or molten but poor when solid (ions are free to move around)
36
what is a covalent bond
formed when a pair of electrons is shared between two atoms leading to the noble gass electronic configurations
37
what properties do simple covalent structures have
- low mp/bp (in terms of weak intermolecular forces)
- poor electrical conductivity
38
2 giant covalent structures
- graphite
- diamond
39
2 uses of graphite
- lubricant
- electrode
40
use of diamond
- cutting tools
41
why graphite can conduct electricity
only bonds with other carbons 3 times - leaving one delocalized electron which becomes shed to create sea of electrons
42
what is the structure of diamond
bonds with 4 carbons - forms tetrahedron
43
describe intermolecular bonds between simple covalent moelecules
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
44
what type of attraction is in covalent bonded molecules
intermolecular between molecules
45
properties of giant covalent
- high mp/bp
-
46
what is silicon (iv) oxide
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)
47
how does diamond compared to silicon (iv) oxide
- 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
48
what is metallic bonding
electrostatic attraction between positive ions in a giant metallic lattice and a 'sea' of delocalised electrons
49
properties of metallic bonding
- good electrical conductivity
- malleable/ductile
50
what is the empirical formula
the simplest whole number ration of the different atoms/ions in a compound
51
what is the mole, mol
the unit amount of substance. one mole contains 6.02 x 10^23 particles (atoms, ions, molecules) this is avogadros constant
52
how to calculate moles
mass(g) / molar mass (g/mol)
53
what is electrolysis
decomposition of an ionic compound, when in molten or aqueous solution, by the passage of an electric current
54
what is the anode
positive electrode
55
what is the cathode
negative electrode
56
what is the electrolyte
the molten/aqueous substance that undergoes electrolysis
57
what type of electrodes do we use
inert. made of platinum or carbon/graphite
58
3 signs that a new substance has formed
- effervescence (fizzing)
- colour change
- temperature changes
59
4 factors affecting rates of reaction
- concentration (pressure for gases)
- surface area of solid reactants
- temperature of the reaction
- presence of a catalyst
60
3 things needed for reaction to occur
- particles must collide
- must collide with successful orientation
- collision must have sufficient energy (activation energy)
61
what is a reversibe reaction
product molecules react with each other or decompose to form reactant molecules
62
what are hydrated salts
salts that contain water of crystallisation which affects their molecular shape/colour
63
what are the 2 examples of hydrated salts
- copper (II) sulfate pentahydrate
- cobalt (II) chloride hexahydrate
64
what color is hydrous and anhydrous copper (II) sulfate pentahydrate
hydrous: blue crystals
anhydrous: white crystals/powder
65
exothermic or endothermic from hydrated copper sulfate to anhydrated copper sulfate
endothermic
66
what is molecular formula of copper (II) sulfate
CuSO4 , 5H20
67
what colour is hydrous and anhydrous cobalt (II) chloride
hydrous: pink crystals
anhydrous: blue crystals
68
from hydrated cobalt (II) chloride to anhydrated cobalt (II) chloride whats the color change?
pink to blue
69
is the reaction from hydrated cobalt (II) chloride to anhydrated cobalt exo or endo
endothermic
70
what is the hydration of CoCl2 and CuSO4 chemical tests used for?
prescence of water
71
molecular formula for copper (II) chloride
CoCl2 , 6H2O
72
what is equilibrium
the rate of the forward and backwards reaction are equal. can only occur in a closed system. concentration of reactants and products remain constant
73
what does the haber process do
ammonia is manufactured by an exothermic reaction
74
what is the equation for haber process
N2 (g) + 3H2 (g) -> 2NH3 (g)
75
where is hydrogen obtained from in haber process
obtained from methane
76
where is nitrogen obtained from in haber process
obtained from the air
77
conditions of haver process
temp = 450 celcius
pressure = 200 atm
catalyst = iron
78
steps of haber process
- 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
79
explain temp used in haber process
high temp favour reverse reaction however rate of reaction is faster. compromise between low yield of products but quicker
80
explain pressure used in haver process
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
explain catalyst used in haner process
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
what does the contact process do
sulfuric acid synthesized by this exothermic reaction
83
what is sulfuric acid used for
fertilisers, soap, detergents,
84
Describe the transfer of charge during electrolysis in terms of electrons
the movement of electrons in the external circuit. cations gain electrons, and anions lose electrons
85
Describe the transfer of charge during electrolysis in terms of ions
ions in the electrolyte carry the charge
86
what is anode
positive electrode
87
what is cathode
negative electrode
88
what is electrolyte
molten/aqueous substance that undergoes electrolysis
89
what is produced at cathode
hydrogen or metals
90
what is produced at anode
non--metals
91
what are the products of electrolysis of molten lead (II) bromide
lead = cathode
bromine = anode
92
what are the products of electrolysis of concentrated aqueous sodium chloride
hydrogen = cathode
chlorine = anode
93
what is brine
concentrated solution of aqueous sodium chloride
94
what is solution remaining in electrolysis of concentrated aqueous sodium chloride
sodium hydroxide
95
what is the rule of what forms at cathode in during electrolysis of aqueous solutions
if its less reactive than hydrogen it will form at cathode
96
what is the rule for what forms at the anode during electrolysis of aqueous solutions
if a halide ion is present, halogen is formed. if no halide ions are present, then oxygen is formed
97
what products are formed during the electrolysis of dilute sulfuric acid
hydrogen = cathode
oxygen = anode
98
dissociation of water in electrolysis of aqueous solutions
H2O ⇌ H+ + OH-
99
what happens if in an aqueous solution there are 2 ions of different concentrations
the more concentrated ion will tend to get discharged over a more dilute ion
100
what happens if a concentrated halide is being electrolysed, what forms at the anode
halogen
101
what happens if a dilute halide is being electrolysed, what forms at the anode
oxygen
102
half equation for reaction at cathode during electrolysis of copper
Cu2+ + 2e– → Cu
103
half equation at anode for hydroxide
4OH– ⟶ O2 + 2H2O + 4e–
104
what happens if copper electrodes are used during electrolysis of copper compound
- 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
why are metal objects electroplated
improve appearance and resistance to corrosion
106
how are half equations written for positive ions
only neutral atom on the right
Li+ + e– → Li
Cu2+ + 2e– → Cu
Al3+ + 3e– → Al
107
halide/halogen half equations
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
hydroxide/oxygen half equation
4OH– → O2 + 2H2O + 4e–
109
what does hydrogen-oxygen fuel cell use
hydrogen and oxygen to produce electricity with water as the only chemical product
110
what is an exothermic reaction
transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings
111
what is an endothermic reaction
takes in thermal energy from the surroundings leading
to a decrease in the temperature of the
surroundings
112
what is transfer of thermal energy during a reaction called
enthalpy change
113
what is activation energy
the minimum
energy that colliding particles must have to react
114
is bond breaking endo or exo
endothermic
115
is bond making exo or endo
exothermic
116
how to test for prescence of water
use anhydrous cobalt (II) chloride/ anhydrous copper (II) sulfate
117
how to test for purity
pure substance boil and melt at a fixed point
118
what is distilled water?
water that has been heated to form a vapour and condensed back to a liquid (contains very few impurities)
119
why is tap water typically not used
more impurities than distilled (interfere with chemical reactions)
120
what is a physical property
characteristic of a substance that can be observed/measured without changing identity of the substance
121
7 physical properties
- color
- hardeness
-malleability
- solubility
- conductivity
- density
-mp/bp
122
what are chemical properties
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
4 things to mention in collision theory
- number of particles per unit volume
- frequency of collisions between particles
- Ek of particles
- activation energy
124
what does a catalyst do
increases rate of reaction and is unchanged at the end of a reaction (decreases activation energy Ea of a reaction
125
practical methods for investigating the rate of reaction
- change in mass of reactant/product
- formation of gas
126
sources of sulfur dioxide
- burning sulfur
- roasting sulfide ores
- oxygen
127
what catalyst does contact process use
vanadium oxide
128
what is redox reactions
involves simultaneous oxidation and reduction
129
define oxidation
- gain oxygen
- loss of electrons
- increase in oxidation
130
define reduction
- loss of oxygen
- gain of electrons
- decrease in oxidation number
131
how identify redox reactions
gain and loss of electrons
132
oxidation number of elements in umcombined state is
0
133
what is oxidation number of a monatomic ion
same charge on the ion
134
sum of oxidation numbers in a compound
0
135
sum of oxidation numbers in an ion
equal to the charge on the ion
136
what is potassium manganate (VII)
oxidising agent often used to test for the presence of reducing agents
137
what happens acidified potassium manganate is added to a reducing agent
purple to colourless
138
what is potassium iodide (KI)
reducing agent often used to test for the presence of oxidising agents
139
what haappens when KI is added to acidified solution of oxidising agent
solution turns red brown due to the formation of iodine
140
what is an oxidising agent
substance that oxidises another substance and is itself reduced
141
what a reducing agent
substance that reduces another substance and is itself oxidised
142
3 indicators
-litmus
- thymolphthalein
- methyl orange
143
color of methyl orange in acid and alkali
acid = red
alkali = yellow
144
color of thymolphthalein in acid and alkali
acid= colourless
alkali = blue
145
what are bases
oxides/hydroxides of metals
146
what are alkalis
soluble bases
147
define acid
proton donors (when added to water they form H+ ions, and presence of H+ ions makes a solution acidic)
148
what type of elements will react with dilute acids
metals above hydrogen in reactivity series
149
what is a strong acid
an acid that is completely dissociated in aqueous solution a
150
what is a weak acid
an acid that is partially dissociated in aq solution
151
what happens when alkalis are added to water
form negative hydroxide ions
152
what makes an aq solution alkaline
presence of OH- ions
153
what happens to ammonium salts when warmed with an alkali
undergo decomposition
154
what can displace ammonia
alkali
155
what is produced when alkali and ammonia are warmed together
salt, water and ammonia
156
what is pH
concentration of H+ ions per dm3 of solution
157
what 2 elements can form amphoteric oxides
aluminium and zinc
158
what is an amphoteric oxide
oxides that react with acids and bases to produce salt and water
159
what 2 oxides are acidic
SO2 and CO2 because they are non metal oxides
160
what are basic oxides
CuO and CaO because they are both metal oxides
161
what is a salt
a compound that is formed when the hydrogen atom in an acid is replaced by a metal
162
2 methods on how to prepare a soluble salt
- adding acid to a solid metal, insoluble base or insoluble carbonate
- reacting a dilute acid and alkali (alkali by titration)
163
how to prepare soluble salt by adding acid to solid metal or insoluble base/carbonate
- 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
how to prepare soluble salt by titration
- 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
how to prepare insoluble salt by precipitation
- mix 2 soluble salts
- filter to remove precipitate
- wash precipitate with distilled water
- leave to dry
166
what is a hydrated substance
substance that is chemically combined with water
167
what is a anhydrous substance
substance containing no water
168
what is water of crystallisation
water molecules present in hydrated crystals
169
what is the periodic table
arrangement of elements in periods and groups and in order of increasing atomic number
170
general trends of group I alkali metals
- relatively soft
- decreasing melting point
- increasing density
- increasing reactivity
171
describe general trends of group VII
- increasing density
- decreasing reactivity
172
state appearance of chlorine at rtp
pale yellow-green gas
173
state appearance of bromine at atp
red brown liquid
174
state appearance of iodine at rtp
a grey-black solid
175
what color is solid iodine
dark grey-black
176
what color is aqueous iodine
brown
177
what color is iodine vapour
purple
178
what is a group VII displacement reaction
a halogen displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide
179
color of chlorine in aq solution
very pale green
180
color of bromine in aq solution
orange but will turn yellow when diluted
181
5 properties of transition metals
- high densities
- high mp
- form coloured compounds
- often act as catalysts
- variable oxidation numbers
182
describe group VIII noble gases
unreactive, monatomic gases, due to having a full valence shell. electronic configuration is extremely stable so these elements are unreactive and inert
183
reaction of metal and cold water
metal + water -> metal hydroxide + hydrogen
184
reaction of metals that react with steam
metal + water _> metal oxide + hydrogen
185
reaction of metal and oxygen
metal + oxygen -> metal oxide
186
3 uses of aluminium due to physical property
- 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
what is an alloy
mixture of metal with other elements
188
what is brass an alloy of
mixture of copper and zinc
189
what is stainless steel an alloy of
mixture of iron, chromium, nickel and carbon
190
why do we alloy
harder, stronger than pure metals and are more useful
191
why are alloys harder and stronger than pure metals
because different sized atoms in alloys mean layers can no longer slide over each other
192
why is stainless steel used in cutlery
hardness and resistance to rusting
193
use of copper due to physical property
- electrical wiring due to good conductivity and ductility
194
what happens to the top of the reactivity series when reacted with cold water (potassium, sodium and calcium)
reacts violently
195
describe reaction of magnesium with water
slow reaction (reacts with steam)
196
describe the relative reactivaties of metals
tendency to form positive ions by displacement reactions
197
explain aluminiums unapparent unreactivity
oxide layer - prevents reaction with water and dilute acids
198
IGCSE Chemistry
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