that three Flashcards
(173 cards)
1
Q
Magnesium needed heating before it would react.
What conclusion can you draw from this?
a. the reaction is reversible
b. the reaction is exothermic
c. the reaction has a high activation energy
d. magnesium has a high melting point
A
C
the reaction has a high activation energy
2
Q
Which two substances are mixtures?
a. air
b. carbon dioxide
c. graphite
d. sodium chloride
e. steel
A
a and e
steel
air
3
Q
What is the test for chlorine gas? (2)
A
damp litmus paper
bleached / turns white
4
Q
What is the test for oxygen, and what will happen if oxygen is present? (2)
A
glowing splint
relights
5
Q
Describe the structure of DNA (3)
A
double helix
2 polymer chains
4 different nucleotides
6
Q
Which two molecules react to make ethyl ethanoate? (2)
A
ethanol
ethanoic acid
7
Q
Explain why HDPE has a higher density than LDPE. (2)
A
the polymer chains / monomers in HDPE are closer together
so there are more atoms per unit volume
8
Q
Polymer A does not melt.
Polymer B melts at 50 degrees celsius.
Why does polymer A bbehave differently to polymer B when heated?
A
A has crosslinks but B doesn’t
9
Q
Monomer X and Y join together to produce a polyester and a small molecule.
Why does this type of polyester melt when it is heated? (2)
A
(the) polyester is thermosoftening
has no crosslinks
10
Q
Name the monomer from which starch is produced.
A
glucose
11
Q
Name the ester produced when ehtanoic acid is reacted with ethanol.
A
ethyl ethanoate
12
Q
Give one reason why the ball and stick model is not a true representation of an ionic structure like potassium sulfide.
A
there are no gaps / sticks between potassium sulfide ions
13
Q
Write the two half equation that occur at the electrodes in a hydrogen fuel cell.
A
H2 –> 2H+ +2e-
O2 + 4H+ + 4e- –> 2H2o
14
Q
What is meant by a strong acid? (2)
A
(acid that is) fully ionised
in water / aqueous solution
15
Q
Explain how a covalent bond holds two atoms together. (2)
A
- electrostatic force of attraction between the positively charged nucleus
- and the negatively charged shared pair of electrons
16
Q
What is the formula of methanoic acid?
A
HCOOH
17
Q
A student compares the rates of reaction of zinc carbonate with an equal volume and concentration of methanoic acid and ethanoic acid.
Methanoic acid has a pH of 2.91
Ethanoic acid has a pH of 3.39
The rate of reaction with methanoic acid is greater than the rate of reaction with ethanoic acid.
Explain why.
You should refer to ions in your answer (3)
A
- methanoic acid has a lower pH
- so it has a higher concentration of H+ ions
- so there are more collisions per unit of time
18
Q
There is a small cube of calcium carbonate with a side length of 0.5cm.
A larger cube of calcium carbonate has sides of 5cm.
Describe how the surface area to volume ration of this larger cube differs from that of the smaller cube.
A
decreases by a factor of 10
19
Q
The rate of reaction is different when a fine powder is used rather than coarse lumps.
Explain why.
You should answer in terms of collision theory. (3)
A
- the surface area is greater
- so there is an increased frequency of collisions
- per unit of time
20
Q
A student tests a gas produced using a burning splint.
Name the gas the student is testing for.
Give the result of a positive test for this gas. (2)
A
hydrogen
pop sound
21
Q
Plan an investigation to find the total mass of dissolved solids in a 100 cm3 sample of drinking water.
Your investigation should produce valid results. (4)
A
Level 2: The design/plan would lead to the production of a valid outcome. All key steps are identified and logically sequenced.
Level 1: The design/plan would not lead to a valid outcome. Some relevant steps are identified, but links are not made clear.
Indicative content
* weigh (evaporating) basin / dish
* add measured volume of water
* weigh (evaporating) basin / dish and water
* heat to evaporate water
* reweigh
* repeat heating until constant mass obtained
* subtract mass of (evaporating) basin / dish from mass
* repeat and calculate a mean, discarding anomalous results
* calculate the mass in 100 cm3 water if necessary
22
Q
What is the stationary phase in paper chromatography?
A
paper
23
Q
What is the mobile phase in paper chromatography?
A
solvent
24
Q
One green ink contains 85% yellow dye and 15% blue dye.
Another green ink contains 75% yellow dye and 25% blue dye.
How would the Rf value of the yellow dye change when measuring the second green ink compared to the first?
A
The Rf value would stay the same
25
Green ink contains more than 2 compounds.
Suggest two reasons why only two spots are seen on the chromatography paper. (2)
- some of the compounds were colourless
- some compounds had the same Rf values
26
On a chromatogram, spots of yellow and blue (from green ink) were very close together.
Which two ways could increase the distance between the spots?
a. allow the solvent front to travel further
b. dry the chromatogram more slowly
c. use a different solvent
d. use a larger beaker
e. use a larger spot of green ink
allow the solvent to travel further
use a different solvent
27
Why is it a problem in chromatography if the start line is drawn in ink?
the ink would dissolve
28
Give one reason why it is difficult to produce models for future climate change. (1)
many alternative theories
many different variables
complex systems
29
In 1869 Dmitri Mendeleev produced his version of the periodic table.
Why did Mendeleev leave gaps for undiscovered elements in his periodic table?
so that elements with similar properties could be placed together
30
Bitumen is a very large hydrocarbon.
Give two reasons why bitumen is not used as a fuel. (2)
(too) viscous
not (very) flammable
high boiling point
31
Suggest two reasons why wood is more sustainable than natural gas as a fuel. (2)
- gas is finite or wood is renewable
- burning wood produces the same amount of carbon dioxide as the trees absorbed (so it is carbon neutral)
32
Name the two substances produced when a hydrocarbon completely combusts in air.
water
carbon dioxide
33
Name the environmental impact caused by oxides of nitrogen.
acid rain
34
Propanoic acid is formed by the oxidation of which organic compound?
propanol
35
Titan is one of Saturn’s moons. Titan is warmer than other moons of Saturn because its atmosphere contains the greenhouse gas methane.
Explain how this greenhouse gas keeps Titan warmer than other moons of Saturn. (3)
- (methane) allows short wavelength radiation to pass through
- (which) is re-emitted by the surface as long(er) wavelength radiation
- (that methane) absorbs / absorbed
36
On Titan, 98.4% of the atmosphere is nitrogen, 1.4% is methane and 0.2% are other gases.
Some scientists think that organisms could have evolved on Titan.
Explain why these organisms could **not** have evolved in the same way life is thought to have evolved on Earth.
- there is little / no oxygen
- so no photosynthesis has occurred
- therefore there is little / no carbon dioxide
37
Which two gases are used in the Haber process to form ammonia. (2)
nitrogen
hydrogen
38
In the Haber process, there is a condenser where ammonia is condensed.
Suggest why ammonia condenses but the other gases do not. (1)
ammonia has a high(er) boiling point
39
Fossil fuels are burned in car engines.
Explain how reducing the amount of sulfur in fossil fuels reduces the erosion of limestone. (4)
sulfur reacts with oxygen to form sulfur dioxide
(so) less sulfur dioxide emitted
(so) less acid rain
(so) less acid rain reacts with limestone
40
Which two of the follwing are renewable sources of methane?
1. animal waste
2. food in landfill
3. nitrogen in the air
4. non-biodegradeable plastics
5. scrap iron
animal waste
food in landfill
41
Compare ethane with ethene. (6)
You should refer to:
- their structure and bonding
- their reactions
Level 2: Scientifically relevant features are identified; the way(s) in which they are similar/different is made clear and (where appropriate) the magnitude of the similarity/difference is noted.
Level 1: Relevant features are identified and features noted.
**Structure and bonding**
- both are hydrocarbons
- both contain two carbon atoms (per molecule)
- ethane contains six hydrogen atoms (per molecule)
- (but) ethene contains four hydrogen atoms (per molecule)
- both have covalent bonds
- ethane contains a single C-C bond
- (but) ethene contains a double bond
- both contain C-H bonds
- both are small molecules
**Reactions**
- both react with oxygen in complete combustion reactions
- to produce water and carbon dioxide
- both react with oxygen in incompelte combustion treactions
- to produce water, carbon monoxide and carbon
- incomplete combustion is more likely with ethene
- ethene decolourises bromine water
- (but) ethane does not decolourise bromine water
- ethene is more reactive (than ethane)
- ethene can react with hydrogen (to produce ethane)
- ethene can react with water (to produce ethanol)
- ethene can react with the halogens (t produce halogenalkanes)
- ethene can undergo addition reactions
- ethene can polymerise (to produce poly(ethene))
42
Describe the conditions needed to crack hydrocarbon molecules. (2)
higher temperature
catalyst **or** steam
43
Alkanes with more carbon atoms will condense lower in the fractionating column than those with less carbon atoms.
Explain why. Refer to the temperature gradient in the fractionating column. (2)
- (alkanes with more carbon atoms have) higher boiling points
- (so) they condense where the column has a higher temperature
44
Titan is one of Saturn’s moons. Titan is warmer than other moons of Saturn because its atmosphere contains the greenhouse gas methane.
Explain how this greenhouse gas keeps Titan warmer than other moons of Saturn. (3)
- (methane) allows short wavelength radiation to pass through
- (which) is re-emitted by the surface as long(er) wavelength radiation
- (that methane) absorbs / absorbed
45
Nitrogen is obtained from the air for the Haber Process.
From where is hydrogen obtained?
natural gas
46
Farmers spread nitrates on to soil to make crops grow better.
The nitrates may get into people’s bodies even if they do not eat the crops.
Explain how this can happen. (2)
nitrates could flow into ground water / rivers
contaminating drinking water
47
Describe how ethanol is produced from sugar solution.
Include the name of this process. (3)
fermentation
add yeast
anaerobic **or** warm
48
Suggest three reasons why copper is now extracted from ores containing a low percentage of copper compounds.
- copper / ores are running out / harder to find
- there are no / very small amounts of high-grade copper ores left
- copper metal is in demand
- **copper** is expensive
- now economical to extract copper from low-grade ores
49
Methanol is used to produce methanoic acid.
What type of substance reacts with methanol to produce methanoic acid?
oxidising agent
*ignore oxygen*
50
Explain why a student carrying out a titration should use a pipette to measure the dilute sulfuric acid and a burette to measure the sodium hydroxide solution she is adding. (2)
- pipette measures a fixed volume
- burette measures variable volume
51
The Earth’s early atmosphere was different to Earth’s atmosphere today.
Scientists think that the Earth’s early atmosphere was like the atmosphere found on Venus today.
On Venus, 96.5% of the atmosphere is carbon dioxide and 0% is oxygen.
On Earth, 0.04% of the atmosphere is carbon dioxide and 20.95% is oxygen.
The percentages of carbon dioxide and oxygen have changed from Earth’s early atmosphere to Earth’s atmosphere today.
Explain the processes that led to these changes. (6)
Level 3: Relevant points (reasons / causes) are identified, given in detail and logically linked to form a clear account.
Level 2: Relevant points (reasons / causes) are identified, and there are attempts at logical linking. The resulting account is not fully clear.
Level 1: Points are identified and stated simply, but their relevance is not clear and there is no attempt at logical linking.
**Indicative content**
**changes**
- carbon dioxide has decreased
- oxygen has increased
**processes**
- volcanic activity released water vapour
- the water vapour condensed to form oceans
- carbon dioxide dissolved into oceans
- carbonates produce sediments
- carbon locked up in sedimentary rocks
- algae and plants evolved / appeared
- algae / plants absorbed carbon dioxide
by photosynthesis
- which also released oxygen
- carbon locked up in fossil fuels
52
Why do alkaline batteries eventually stop working?
a reactant is used up
53
Why can alkaline batteries **not** be recharged?
the reaction is not reversible
54
Explain why graphite conducts electricity.
Answer in terms of the structure and bonding in graphite. (3)
- each carbon atom (in graphite) forms 3 (covalent) bonds
- (and) for each carbon atom there is one delocalised electron
- which can move through the structure / carry a charge
55
Mendeleev left spaces in his periodic table because he thought missing elements belonged there.
Why did Mendeleev’s periodic table become more widely accepted than previous versions? (3)
- Mendeleev had predicted the properties of missing elements
- elements were discovered (that filled the spaces)
- properties (of these elements) matched Mendeleev’s predictions
56
Explain why an acid can be described as both strong and dilute. (2)
- completely ionised (in aqueous solution)
- small amount of acid per unit volume
*do not allow low concentration*
57
In an industrial factory, sodium is reacted with titanium tetrachloride.
Explain why it would be hazardous if water came into contact with sodium. (1)
very exothermic reaction
produces a corrosive solution
hydrogen produced which is flammable
58
Sodium is in Group 1 of the modern periodic table.
Describe what you would see when sodium reacts with chlorine. (2)
- solid forms
- flame
- colour of gas / chlorine disappears / fades
59
Explain why ammonia has a low boiling point.
You should refer to structure and bonding in your answer. (3)
- small molecule / simple molecular
- weak intermolecular forces
- (that) require little energy to overcome
60
Suggest a limitation of the dot and cross diagram.
only two-dimensional
61
Some diesel trains are being converted to run on hydrogen fuel cells.
Explain why newspaper articles referred to the converted trains as the new ‘steam trains’. (2)
- hydrogen is oxidised
- water produced / released as a gas / vapour / steam
62
Explain why an aluminium mixture containing cryolite is used as the electrolyte instead of using only aluminium oxide. (2)
- mixture has lower melting point
- less **energy** needed
63
Explain why the positive electrode in electrolysis must continually be replaced. (3)
electrode reacts with oxygen
because it is made of carbon / graphite
to produce carbon dioxide
64
Explain why sodium chloride solution cannot be used as the electrolyte to produce sodium metal. (2)
hydrogen (gas) would be produced
(because) sodium is more reactive than hydrogen
65
Give **three** conclusions that can be drawn about the rate of reaction between magnesium and dilute hydrochloric acid in the investigation. (3)
- (rate) decreases / slows down
- (rate decreases / slows down) more slowly as time increases
- (rate) becomes zero at 60s
66
Explain what would happen to each of the follwing nails.
Test tube 1:
iron nail
in water
Test tube 2:
iron nail
in dry air
with rubber stopper
Test tube 3:
iron nail
in boiled water
with a layer of oil above the water
Test tube 4:
painted iron nail
in water
Test tube 5:
stainless steel nail
in water
- Tube 1: (nail) rusts because oxygen **and** water present
- Tube 2: (nail) doesn't rust because no water
- Tube 3: (nail) doesn't rust because no oxygen
- Tube 4: (nail) doesn't rust because paint is a barrier / protective layer / protective coating
- Tube 5: (nail) does not rust because stainless steel is resistant to corrosion / does not corrode
67
Explain how fixing magnesium to steel ships prevents the steel from rusting. (2)
- magesium is more reactive (than iron / steel)
- (so magnesium) provide sacrificial protection
68
- Explain why aluminium window frames do **not** corrode after they are made. (2)
- (aluminium has a coating of) aluminium oxide
- (so the aluminium oxide) protects the metal / prevents oxygen / water from reaching the metal
69
Describe a test to show whether that a hydrocabon is unsaturated. (2)
- (add) bromine (water)
- (changes from) orange / brown to colourless
70
Which **two** other materials are used to make glass by heating with sand?
limestone and sodium carbonate
71
Suggest why poly(ethene), which is a thermosoftening polymer, is easier to recycle than thermosetting polymers. (2)
- melts
- can be reshaped
72
Suggest **three** reasons why recycling scrap copper is a more sustainable way of obtaining copper than processing copper ores. (3)
- recycling conserves copper ores
- recycling uses less energy
- recycling reduces waste
- mining / quarrying causes environmental impact
73
Suggest **two** reasons why phytomining has not been widely used to extract copper apart from producing low amounts of copper.
- takes a long time
- new technology
- land not available
- high grade ores still available
74
Describe how copper is extracted from low-grade ores by phytomining. (4)
- grow plants
- plants are burnt (to produce ash)
- dissolve ash in acid
- electrolysis / displacement of solution (containing copper compound)
75
Which two metals are used in the alloy of bronze?
tin and copper
76
Describe how ceramic food plates are produced from clay. (2)
- (wet) clay is shaped
- (and) heated in a furnace
77
Give five examples of formulations.
- fuels
- foods
- medicine
- cleaning agents
- fertilisers
- paints alloys
78
What percentage of gold is 18 carat gold?
75%
79
What percentage of gold is 24 carat gold?
100%
80
Name 3 metals in the alloy of stainless steel.
- chromium
- iron
- nickel
81
What is borosilicate glass made from?
sand and boron trioxide
82
How is the melting point of borosilicate glass different to that of soda-lime glass?
it has a higher melting point
83
Most composites are made of which two materials?
- matrix
- reinforcement
84
Give two properties of high carbon steel.
strong but brittle
85
Give two properties of low carbon steel.
soft and more easily shaped
86
Which two metals make up the alloy of brass?
copper and zinc
87
Give two properties of stainless steel.
hard and resistant to corrosion
88
Give two examples of composites.
carbon fibre and fibreglass
89
Why will a painted iron nail not rust when exposed to air and water?
paint is a barrier
90
90% of red brass is copper and 10% is zinc.
70% of yellow brass is copper and 30% is zinc.
Explain why red brass is softer than yellow brass. (2)
- (red brass has) less zinc / more copper
- (so) layers are less distorted / layers slide more easily
91
Which **two** substances have intermolecular forces between particles?
diamond
magnesium
poly(ethene)
sodium chloride
water
water and poly(ethene)
92
Compare the structure and bonding of:
- carbon dioxide
- magnesium oxide
- silicon dioxide
(6)
Level 2: Scientifically relevant features are identified; the way(s) in which they are similar/different is made clear and (where appropriate) the magnitude of the similarity/difference is noted.
Level 1: Relevant features are identified and differences noted.
Indicative content
* (both) carbon dioxide and silicon dioxide are made up of atoms
* (but) magnesium oxide is made up of ions
/
* (both) silicon dioxide and magnesium oxide are giant structures
* (but) carbon dioxide is small molecules
* with weak intermolecular forces
/
* all three compounds have strong bonds
* (both) carbon dioxide and silicon dioxide are formed from two
non-metals
* (so) bonds formed are covalent
* (so) electron (pairs) are shared (between atoms)
* (but) magnesium oxide is formed from a metal and a non-metal
* (so) bonds in magnesium oxide are ionic
* (so) electrons are transferred
* from magnesium to oxygen
* two electrons are transferred
/
* bonds in silicon dioxide are single bonds
* (where) each silicon forms four bonds
* (and) each oxygen forms two bonds
* (but) in carbon dioxide the bonds are double bonds
* (where) carbon forms two double bonds
* (and) oxygen forms one double bond
/
ignore properties e.g. melting point, electrical conductivity
93
A student added copper metal to colourless silver nitrate solution.
The student observed:
- pale grey crystals forming
- the solution turning blue
Explain how these observations show that silver is less reactive than copper. (3)
- the (grey) crystals are silver
- the copper ions (produced) are blue
- (because) copper displaces
silver
94
A student is given metals **X**, **Y** and **Z** to identify.
The metals are magnesium iron and copper.
Plan an investigation to identify the three metals by comparing their reactions with dilute hydrochloric acid.
Your plan should give valid results. (4)
Level 2: The method would lead to the production of a valid outcome. The key steps are identified and logically sequenced.
Level 1: The method would not lead to a valid outcome. Some relevant steps are identified, but links are not made clear.
Indicative content
/
Key steps
* add the metals to (dilute) hydrochloric acid
* measure temperature change **or** compare rate of bubbling **or** compare colour of resulting solution
/
for copper:
* no reaction
* shown by no temperature change **or** shown by no bubbles
/
for magnesium and iron:
* magnesium increases in temperature more than iron **or** magnesium bubbles faster than iron **or** magnesium forms a colourless solution and iron forms a coloured solution
/
Control variables
* same concentration / volume of hydrochloric acid
* same mass / moles of metal
* same particle size of metal
* same temperature (of acid if comparing rate of bubbling)
95
Give three reasons why reactions with high atom economy are used in industry. (3)
- sustainable development
- for economic reasons
- to produce a high(er) % of useful product
- reduce waste
96
A student investigated the electrolysis of copper chromate solution.
Describe how a solid forms at the negative electrode. (3)
- copper ions gain 2 electrons
- (to) form copper (atoms)
*half equation scores 3 marks*
97
Describe three differences between the nuclear model of the atom and the plum pudding model. (3)
- mostly empty space
- the positive charge is in the nucleus
- the mass is concentrated in the nucleus
- electrons and nucleus are seperate
- has a nucleus
98
A student suggested that Mendeleev's reason for reversing the order of some pairs of elements was to arrange the elements in order of atomic number.
Explain why the student's suggestion **cannot** be correct. (2)
- atomic number is the number of protons
- protons had not been discovered yet
99
Give the correct reason why Mendeleev reversed the order of some pairs of elements. (1)
so their properties matched the
rest of the **group**
100
What is meant by 'activation energy'?
the (minimum) energy needed for particles to react
**or**
the (minimum) energy needed for a reaction to occur
101
Give three advantages of using hydrogen fuel cells instead of using rechargeable cells to power cars. (3)
* no toxic chemicals to dispose of at the end of the cell’s life
* take less time to refuel (than to recharge rechargeable cells)
* travel further before refuelling (than before recharging rechargeable cells)
* no loss of efficiency (over time)
102
Give two half equations for any of the reactions that happen at the positive and negative electrode in a hydrogen fuel cell. (2)
* H2 → 2H+ + 2e-
* O2 + 4H+ + 4e- → 2H2O
* H2 + 2OH- → 2H2O + 2e-
* O2 + 2H2O + 4e- → 4OH
103
# A square with black circles.
Give two limitations of this simple particle model for hydrogen gas. (2)
- hydrogen is not shown as H2 / molecules
- particles are shown as spheres
- particles are shown as solid
- does not show the (weak) forces (between particles)
- does not show the movement / speed (of particles)
- is only two-dimensional
104
Explain the trend in boiling points of halogens. (4)
- (boiling point) increases (down the table / group)
- (because) the relative formula / molecular mass increases **or** (because) the size of the molecule increases
- (so) the intermolecular forces increase (in strength)
- (so) more energy is needed to overcome the intermolecular forces
105
Why is it **not** correct to say that the boiling point of a single bromine molecule is 59 °C? (1)
boiling point is a bulk property
106
Explain why the reactivity of the halogens decreases going down the group. (3)
- (going down the group) the outer electrons / shell become further from the nucleus
- (so) the nucleus has less attraction for the outer electrons / shell
- (so) an electron is gained less
easily
107
13.3 cm3 of 0.0500 mol/dm3 citric acid solution was needed to neutralise 25.0 cm3 of sodium hydroxide solution.
The equation for the reaction is:
3NaOH + C6H8O7 → C6H5O7Na3 + 3H2O
Calculate the concentration of the sodium hydroxide solution in mol/dm3 (3)
0.0798
108
Give two reasons why a burette is used in titration.
- can add acid in small increments / drop-by-drop / slowly
- more accurate than a measuring cylinder
- can measure variable volumes
109
Citric acid is a solid.
A student investigated the temperature change during the reaction between citric acid and sodium hydrogencarbonate solution.
This is the method used.
1. Pour 25 cm3 of sodium hydrogencarbonate solution into a polystyrene cup.
2. Measure the temperature of the sodium hydrogencarbonate solution.
3. Add 0.20 g of citric acid to the polystyrene cup.
4. Stir the solution.
5. Measure the temperature of the solution.
6. Repeat steps 3 to 5 until a total of 2.00 g of citric acid has been added.
On the graph:
Temperature of the solution falls constantly from the initial temperature of 16.8°C until 11°C after which 1.5g of citric acid has been added.
After 1.5g of citric acid had been added, the temperature increases by 1.25°C to 10.25°C.
Explain the shape of the graph in terms of the energy transfers taking place. (3)
- the temperature decreases (initially) because energy is taken in (by the reaction from the solution)
- when 1.5 g (of citric acid) is added the sodium hydrogencarbonate has all reacted **or** from 1.5 g the citric acid is in excess **or** when 1.5 g (of citric acid) is added the reaction is complete
- (so) the temperature increases as energy is transferred from the room to the solution
110
Citric acid is a solid.
A student investigated the temperature change during the reaction between citric acid and sodium hydrogencarbonate solution.
This is the method used.
1. Pour 25 cm3 of sodium hydrogencarbonate solution into a polystyrene cup.
2. Measure the temperature of the sodium hydrogencarbonate solution.
3. Add 0.20 g of citric acid to the polystyrene cup.
4. Stir the solution.
5. Measure the temperature of the solution.
6. Repeat steps 3 to 5 until a total of 2.00 g of citric acid has been added.
On the graph:
Temperature of the solution falls constantly from the initial temperature of 16.8°C until 11°C after which 1.5g of citric acid has been added.
After 1.5g of citric acid had been added, the temperature increases by 1.25°C to 10.25°C.
A second student repeated the investigation using a metal container instead of the polystyrene cup. The container and the cup were the same size and shape.
What would a line on the graph showing results using the metal container just until 1.00g of citric had been added look like?
The starting temperature of the solution was the same.
Explain your answer. (3)
- less steep line starting at 16.8 °C **and** reaching 1.00 g (of citric acid)
- (as) metal is a better conductor
- (so) more energy is absorbed (from the surroundings)
111
This is part of the method a student used for a titration.
1. Measure 25.0 cm3 of the sodium hydroxide solution into a conical flask
using a pipette.
2. Add a few drops of indicator to the flask.
3. Fill a burette with citric acid solution.
Describe how the student would complete the titration. (3)
- add the citric acid (to the flask) until there is a (permanent) **colour change**
- measure / record the volume (of citric acid) added
any **one** from:
- swirl
- use a white tile
- add citric acid dropwise (near the endpoint)
- repeat **and** calculate a mean
112
Give three uses of ethanol.
- antiseptic
- alcoholic drinks
- fuel
- solvent / perfume / aftershave
113
What type of chemical is used as a catalyst in the reaction between ethanol and ethanoic acid?
acid
114
What does volatile mean?
evaporates easily / quickly
115
Why does crude oil have to fractionally distillated?
it is a mixture **or** contains hydrocarbons with different boiling points
116
A building material consists of a wood particle reinforcement embedded in a poly(ethene) matrix.
What general name is given to materials like this?
composites
117
Why are many fabrics made from polymers instead of wool?
a. polymers are man-made
b. polymers are more hard-wearing
c. wool is more easily available
d. wool is more flame resistant
b. polymers are more hard-wearing
118
What shape is a Buckminsterfullerene molecule?
spherical
119
Give three uses of fullerenes.
* drug delivery (round the body)
* hydrogen storage
* anti-oxidants
* reduction of bacterial growth
* catalysts
* (cylindrical fullerenes for) strengthening materials
* (spherical fullerenes for) lubricants
120
Explain why graphite is:
- a good electrical conductor
- soft and slippery
You should answer in terms of structure and bonding. (6)
**Level 3:** Relevant points (reasons/causes) are identified, given in detail and logically linked to form a clear account.
**Level 2:** Relevant points (reasons/causes) are identified, and there are attempts at logical linking. The resulting account is not fully clear.
**Level 1:** Points are identified and stated simply, but their relevance is not clear and there is no attempt at logical linking.
**Indicative content**
- bonds are covalent
- giant / macromolecular structure
/
- three (covalent) bonds per carbon atom **or** only three electrons per carbon atom used in (covalent) bonds
- so one electron per carbon atom (is delocalised)
- these delocalised electrons
- can move through the structure
- carry (electrical) charge
- so graphite conducts electricity
/
- layered structure
- of (Interlocking) hexagonal rings
- with weak (intermolecular) forces between layers **or** no covalent bonds between layers
- so the layers can slide over each other
- so graphite is soft and slippery
121
Give 5 observations you could make when a small piece of potassium is added to water.
- flame
- effervescence
122
What are the products in the reaction of potassium and water?
potassium **hydroxide** and hydrogen
123
Explain why sodium oxide has a high melting point. (3)
- giant structure / lattice
- strong electrostatic forces of attraction between oppositely charged ions
- (forces / bonds) require large amounts of energy to break
124
Write an ionic equation for the neutralisation of hydrochloric acid with potassium hydroxide.
H+ + OH− → H2O
125
Which of the following will react with hydrochloric acid to produce a salt?
1. copper
2. copper carbonate
3. copper oxide
copper carabonate and copper oxide
126
Will copper displace hydrogen?
no
127
What is higher in the reactivity series: copper or hydrogen
hydrogen
128
A student makes crystals of magnesium sulfate.
This is the method used.
1. Add sulfuric acid to a beaker.
2. Warm the sulfuric acid.
3. Add a spatula of magnesium oxide to the beaker.
4. Stir the mixture.
5. Repeat steps 3 and 4 until there is magnesium oxide remaining in the beaker.
6. Filter the mixture.
7. Evaporate the filtrate gently until crystals start to form.
8. Leave the solution to finish crystallising.
Give a reason for **step 2**.
to increase the rate of reaction
129
A student makes crystals of magnesium sulfate.
This is the method used.
1. Add sulfuric acid to a beaker.
2. Warm the sulfuric acid.
3. Add a spatula of magnesium oxide to the beaker.
4. Stir the mixture.
5. Repeat steps 3 and 4 until there is magnesium oxide remaining in the beaker.
6. Filter the mixture.
7. Evaporate the filtrate gently until crystals start to form.
8. Leave the solution to finish crystallising.
Give a reason for **step 5**.
to make sure all of the (sulfuric) acid reacts
130
A student makes crystals of magnesium sulfate.
This is the method used.
1. Add sulfuric acid to a beaker.
2. Warm the sulfuric acid.
3. Add a spatula of magnesium oxide to the beaker.
4. Stir the mixture.
5. Repeat steps 3 and 4 until there is magnesium oxide remaining in the beaker.
6. Filter the mixture.
7. Evaporate the filtrate gently until crystals start to form.
8. Leave the solution to finish crystallising.
Give a reason for **step 6**.
to remove excess magnesium oxide
131
A student makes crystals of magnesium sulfate.
This is the method used.
1. Add sulfuric acid to a beaker.
2. Warm the sulfuric acid.
3. Add a spatula of magnesium oxide to the beaker.
4. Stir the mixture.
5. Repeat steps 3 and 4 until there is magnesium oxide remaining in the beaker.
6. Filter the mixture.
7. Evaporate the filtrate gently until crystals start to form.
8. Leave the solution to finish crystallising.
What are the two ways the filtrate could be evaporated gently in **step 7**?
using a water bath **or** electric heater
132
Calculate the volume of chlorine needed to react with 14g of iron in dm^3.
2Fe + 3Cl2 → 2FeCl3
9
133
Explain why allows are harder than pure metals. (3)
- atoms are different sizes
- layers (of atoms in alloys) are distorted
- layers slide over each other less easily (than pure metals)
134
A student wants to compare the reactivity of an unknown metal, Q, with that of zinc.
Both metals are more reactive than silver.
The student is provided with:
* silver nitrate solution
* metal Q powder
* zinc powder
* a thermometer
* normal laboratory equipment.
No other chemicals are available.
Describe a method the student could use to compare the reactivity of metal Q with that of zinc.
Your method should give valid results. (4)
- measure temperature change
- when each metal is added to the silver nitrate solution
- same volume / concentration of solution **or** same mass / moles of metal
- the greater the temperature change the more reactive
135
Electrolysis and chemical cells both involve chemical reactions and electricity.
Explain the difference between the processes en electrolysis and in a chemical cell. (2)
electrolysis uses electricity to produce a chemical reaction **but** chemical cells use a chemical reaction to produce electricity
136
Bromine is produced at the anode during the electrolysis of lead bromide.
Write the balanced half equation for the production of bromine. (2)
2Br-→ Br2 + 2e-
137
Copper nitrate solution is electrolysed.
What are the products at each electrode? (2)
positive electrode: oxygen
negative electrode: copper
138
Potassium iodide solution is electrolysed.
What are the products at each electrode? (2)
positive electrode: iodine
negative electrode: hydrogen
139
Students investigated the electrolysis of copper nitrate solution.
When they tried to measure the mass of the copper produced, some copper did stick to the cathode and fell off.
Suggest how the students could find the total mass of copper produced. (6)
- rinse / wash and dry negative electrode
- calculate change in mass of negative electrode
- filter the mixture
- wash and dry copper
- weigh the copper collected
- add to increase in mass of the cathode
140
Suggest why the blue colour of copper nitrate solution fades during electrolysis.
copper ions are discharged / removed (from the solution)
141
Hydrogen chloride and ethanoic acid both dissolve in water.
All hydrogen chloride molecules ionise in water.
Approximately 1% of ethanoic acid molecules ionise in water.
A solution is made by dissolving 1g of hydrogen chloride in 1 dm^3 of water.
Select the correct description of this solution:
1. concentrated solution of a strong acid
2. concentrated solution of a weak acid
3. dilute solution of a strong acid
4. dilute solution of a weak acid
dilute solution of a strong acid
142
Hydrogen chloride and ethanoic acid both dissolve in water.
All hydrogen chloride molecules ionise in water.
Approximately 1% of ethanoic acid molecules ionise in water.
Select the solution that would have the lowest pH:
1. 0.1mol/dm^3 ethanoic acid solution
2. 0.1mol/dm^3 hydrogen chloride solution
3. 1.0mol/dm^3 ethanoic acid solution
4. 1.0mol/dm^3 hydrogen chloride solution
1.0mol/dm^3 hydrogen chloride solution
143
A student investigated the concentration of a solution of sodium hydroxide by titration box with a 0.0480 mol/dm3 ethanedioic acid solution.
This is the method used:
1. Measure 25.0 cm3 of the sodium hydroxide solution into a conical flask using a 25.0 cm3 pipette.
2. Add two drops of indicator to the sodium hydroxide solution.
3. Fill a burette with the 0.0480 mol/dm3 ethanedioic acid solution to the 0.00 cm3 mark.
4. Add the ethanedioic acid solution to the sodium hydroxide solution until the indicator changes colour.
5. Read the burette to find the volume of the ethanedioic acid solution used.
Suggest four improvents to the method that would increase the accuuracy of the result.
- swirl
- use a white tile
- add acid dropwise
- repeat **and** calculate a mean
144
Gallium was discovered six years after Mendeleev published his periodic table.
Give **two** reasons why the discovery of gallium helped Mendeleev's periodic table to become accepted.
- fitted a gap (Mendeleev had left)
- (gallium's properties) matched the rest of the group / properties predicted correctly
145
Give three examples of exothermic reactions.
- combustion
- oxidation
- neutralisation
145
What is a battery?
two or more cells connected together in series to provide a greater voltage
146
Give two endothermic reactions.
- thermal decomposition
- reaction of citric acid and sodium hydrogen carbonate
147
What is the ionic equation of ANY neutralisation reaction?
H+ + OH- → H2O
148
Tennessine was first identified by a small group of scientists in 2010.
Suggest one reason why tennessine was not accepted as a new element by other scientists until 2015.
(time needed for) peer review
149
What does uncertainty show?
range about the mean value
150
Plan a method to make pure, dry crystals of zinc chloride from zinc carbonate and a dilute acid. (6)
**Level 3:** The method would lead to the production of a valid outcome. The key steps are identified and logically sequenced.
**Level 2:** The method would not necessarily lead to a valid outcome. Most steps are identified, but the method is not fully logically sequenced.
**Level 1:** The method would not lead to a valid outcome. Some relevant steps are identified, but links are not made clear.
**Indicative content**
* use zinc carbonate and hydrochloric acid
* **add zinc carbonate to the (hydrochloric) acid**
* in a beaker
* stir
* **continue adding until the zinc carbonate is in excess**
* shown by excess solid
* and no more effervescence
* **filter (the reaction mixture)**
* to remove the excess zinc carbonate
* **heat the solution**
* using a water bath or electric heater
* to crystallisation point
* **leave the solution to crystallise**
* pat crystals dry with filter paper
151
Explain why a reaction released energy to the surroundings. (2)
- energy is supplied to break bonds **and** energy is released in making / forming bonds
- energy released in making bonds is greater than energy supplied to break bonds
152
Explain why methane and poly(ethene) exist in different states at room temperature. (4)
- methane has (much) smaller molecules
- (so) has weaker intermolecular forces
- (so) less energy is required to overcome (the forces)
- (so the) boiling / melting point is lower
**or**
- poly(ethene) has (much) larger molecules
- (so) has stronger intermolecular forces
- (so) more energy is required to overcome (the forces)
- (so the) boiling / melting point is higher
153
Describe how metals conduct electricity. (3)
- (metals have) delocalised electrons
- the electrons carry charge
- electrons move through the structure / metal
154
Suggest why alloys do **not** conduct electricity as well as pure metals. (2)
- in alloys different sized atoms distort the layers
- (so) the movement of (delocalised) electrons is restricted
155
A student investigated the electrolysis of an aqueous solution.
Explain how oxygen was produced from water during the electrolysis of this aqueous solution. (5)
- water molecules break down
- to form (H+ and) OH- ions
- OH- ions move to the positive electrode
- (because) like charges attract
- OH- ions are discharged / oxidised to give oxygen (molecules)
156
Explain why argon does not form compounds.
Answer in terms of electrons. (2)
- argon has a full outer shell of electrons **or** argon has a stable arrangement of electrons
- (so) argon does not share / transfer electrons
157
Suggest two observations that could be made when barium reacts with hydrochloric acid.
- effervescense / fizzing / bubbling
- temperature increase
- barium disappears
158
Self-cleaning windows are coated with a layer of nanoparticles of titanium dioxide.
TItanium dioxide:
- helps sunlight break down dirt particles
- attracts water, so dirt is washed away by rain.
Nanoparticles of titanium dioxide are used instead of fine particles of titanium dioxide for coating self-cleaning windows.
Suggest two reasons why.
- high**er** surface area to volume ratio
- more light gets through
- thinner coating / less material needed
159
Give three differences between the physical properties of the elements in Group 1 and those of the transition metals.
- softer
- lower densities
- less strong
- lower melting / boiling points
160
How does a reaction profile show that a reaction is exothermic?
(level) of products is below (level of) reactants
161
Describe the structure and bonding of diamond. (3)
- giant structure
- covalent bonds
- 4 bonds per carbon atom
162
Explain why diamond has a very high melting point. (3)
- strong covalent bonds
- bonds must be broken
- a lot of energy required
163
Suggest three reasons why spherical fullerenes are suitable for moving drugs around the body.
- hollow
- large SA to volume ratio
- unreactive
- not toxic
164
A student adds ZnO to HCl until the ZnO is in excess.
Give one observation that the student could make to ZnO is in excess.
solid remaining
165
When reacting zinc oxide and hydrochloric acid, why is excess zinc oxide used instead of excess hydrochloric acid?
separation / removal of zinc oxide is easier
166
Suggest one reason why a mesh is sometimes used to keep the products of electrolysis apart.
so they don't react
167
Explain how an alkaline solution is prodced when sodium chloride solution is electrolysed.
Refer to the processes at the electrodes. (3)
- sodium ions and hydroxide ions are left (in the solution)
- (because) hydrogen ions are discharged / reduced (at the negative electrode to form hydrogen)
- (and because) chloride ions are discharged / oxidised (at the positive electrode to form chlorine)
168
Carbon can be obtained by heating coal.
Alluminium is obtained from aluminium oxide.
Explain why aluminium is more expensive than carbon. (2)
- more energy is needed
- (because) aluminium is obtained by electrolysis
169
2Si2H6(g) + 7O2(g) → 4SiO2(s) + 6H2O(g)
30 cm3 of Si2H6 is reacted with 150 cm3 (an excess) of oxygen.
Calculate the total volume of gases present after the reaction. (4)
135cm^3
170
Explain why the pH of an acid depends on:
- the strength of the acid
- the concentration of the acid
(4)
**Level 3:** Relevant points (reasons / causes) are identified, given in detail and logically linked to form a clear account.
**Level 2:** Relevant points (reasons / causes) are identified, and there are attempts at logical linking. The resulting account is not fully clear.
**Indicative content**
**General principle**
* pH depends on H+ ion concentration
* the higher the concentration of H+ ions the lower the pH
/
**Strength**
* the stronger an acid the greater the ionisation / dissociation (in aqueous solution)
* (so) the stronger the acid the lower the pH
/
**Concentration**
* the higher the concentration of an acid the more acid / solute in the same volume (of solution)
* (so) the higher the concentration of the acid the lower the pH
171
A student titrated sulfuric acid with barium hydroxide solution.
H2SO4(aq) + Ba(OH)2(aq) → BaSO4(s) + 2H2O(l)
The student measured the electrical conductivity of the mixture during the titration.
Explain why the electrical conductivity of the mixture was zero when the sulfuric acid had just been neutralised.
Refer to ions in your answer. (3)
- there are no ions that are free to move
- (because) barium sulphate is solid
- (and) hydrogen ions have reacted with hydroxide ions to produce water
172
A student titrated sulfuric acid with barium hydroxide solution.
H2SO4(aq) + Ba(OH)2(aq) → BaSO4(s) + 2H2O(l)
The student measured the electrical conductivity of the mixture during the titration.
The student then added a further 10cm^3 of barium hydroxide solution once the sulfuric acid had just been neutralised.
Give one reason why the electrical conductiivity of the mixture increased.
mixture now contains barium ions **and** hydroxide ions that are free to move
