2022 AQA GCSE Chemistry 8462 模擬試題連答案詳解

An exothermic reaction is one that transfers energy to the surroundings, usually in the form of heat, raising the temperature of the surroundings. A self-heating can of coffee uses this type of reaction to warm the drink without an external heat source.

1 mark for correct answer B.
Award 0 marks for any other response.

In an endothermic reaction, energy is absorbed from the surroundings. Because energy is taken in, the chemical energy of the products is greater than the chemical energy of the reactants.

1 mark for correct answer A.
Award 0 marks for any other response.

Decreasing the temperature decreases the kinetic energy of the reacting particles. This means they move more slowly, collide less frequently, and with less energy, which decreases the rate of the chemical reaction.

1 mark for correct answer C.
Award 0 marks for any other response.

Fractional distillation separates hydrocarbons based on their boiling points. The fractionating column is hotter at the bottom and cooler at the top. Hydrocarbons condense when they reach the level in the column where the temperature is equal to their boiling point.

1 mark for correct answer B.
Award 0 marks for any other response.

Alkanes are saturated hydrocarbons containing only single covalent bonds. Their general chemical formula is represented as \(C_nH_{2n+2}\), where \(n\) is the number of carbon atoms.

1 mark for correct answer B.
Award 0 marks for any other response.

The nitrogen gas used as a raw material in the industrial Haber process is extracted directly from the atmosphere (air), which is composed of approximately 78% nitrogen gas.

1 mark for correct answer A.
Award 0 marks for any other response.

A life cycle assessment (LCA) assesses the environmental impact of a product. The final stage is the disposal of the product at the end of its useful life, which includes assessing impacts associated with landfilling, incineration, or recycling.

1 mark for correct answer D.
Award 0 marks for any other response.

Sodium chloride exists as a giant ionic lattice held together by strong electrostatic forces of attraction between oppositely charged sodium ions (\(\text{Na}^+\)) and chloride ions (\(\text{Cl}^-\)). These strong bonds require a large amount of thermal energy to overcome, resulting in a high melting point.

1 mark for correct answer C.
Award 0 marks for any other response.

An endothermic reaction takes in energy from the surroundings, which causes the temperature of the surroundings (and the reaction mixture) to decrease. Therefore, the reaction is endothermic because energy is taken in from the surroundings.

[1 mark] D - The reaction is endothermic because energy is taken in from the surroundings.

Magnesium is the most reactive of the four metals listed. Highly reactive metals react vigorously with dilute hydrochloric acid, producing bubbles of hydrogen gas most rapidly. Copper does not react with dilute acid, while iron and zinc react more slowly than magnesium.

[1 mark] C - Magnesium

Water is a simple molecular substance. Covalent bonds are formed when non-metal atoms (hydrogen and oxygen) share pairs of electrons.

[1 mark] A - Electrons are shared between hydrogen and oxygen atoms to form covalent bonds.

To obtain large, pure crystals of a soluble salt, the solution should be heated gently to evaporate some of the water (to form a saturated solution), then left to cool and crystallise slowly. The crystals can then be filtered and dried. Heating to complete dryness would result in an anhydrous powder, not nice crystals.

[1 mark] C - Heat the solution gently to evaporate some water, leave it to crystallise, then filter and dry the crystals.

In graphite, each carbon atom is covalently bonded to three other carbon atoms in hexagonal layers. This leaves one outer shell electron per carbon atom delocalised. These delocalised electrons are free to move throughout the entire structure and carry electrical charge.

[1 mark] C - It has delocalised electrons that are free to move through the structure.

The atomic number is 11, which means there are 11 protons. In a neutral atom, the number of electrons equals the number of protons, which is 11. The number of neutrons is the mass number minus the atomic number: \(23 - 11 = 12\).

[1 mark] B - Protons = 11, Neutrons = 12, Electrons = 11

During the electrolysis of molten sodium chloride, positive sodium ions (\(\text{Na}^+\)) are attracted to the negative electrode (cathode). Here, they gain electrons (reduction) to form sodium metal (\(\text{Na}\)). Hydrogen is not produced because the electrolyte is molten, not an aqueous solution.

[1 mark] D - Sodium metal

By the law of conservation of mass, the total mass of reactants equals the total mass of products. Therefore: \(\text{mass of carbon} + \text{mass of oxygen} = \text{mass of carbon dioxide}\). Substituting the values: \(12.0\text{ g} + \text{mass of oxygen} = 44.0\text{ g}\). So, \(\text{mass of oxygen} = 44.0\text{ g} - 12.0\text{ g} = 32.0\text{ g}\).

[1 mark] B - 32.0 g

Since the temperature of the mixture increases, energy has been transferred to the surroundings. This means the reaction is exothermic.

1 mark for the correct option D. Award 0 marks for any other option.

Sodium chloride contains ionic bonding because it is formed from a metal (sodium) and a non-metal (chlorine). Carbon dioxide, water, and oxygen are non-metals bonded together, which forms covalent bonds.

1 mark for the correct option B. Award 0 marks for any other option.

Group 0 elements have a stable, full outer shell of electrons, which means they do not need to lose, gain, or share electrons to become stable.

1 mark for the correct option A. Award 0 marks for any other option.

Zinc is more reactive than copper in the reactivity series, which allows zinc to displace copper from its salt solution.

1 mark for the correct option B. Award 0 marks for any other option.

According to the law of conservation of mass, the mass of the products equals the mass of the reactants. Therefore, Mass of oxygen = Mass of magnesium oxide - Mass of magnesium = \( 8.0\text{ g} - 4.8\text{ g} = 3.2\text{ g} \).

1 mark for the correct option C. Award 0 marks for any other option.

1. Calculate the temperature change: \(14.6\ ^\circ\text{C} - 20.2\ ^\circ\text{C} = -5.6\ ^\circ\text{C}\) (which is a decrease of \(5.6\ ^\circ\text{C}\)).
2. The reaction is endothermic because the temperature of the surroundings decreased, indicating that energy has been taken in from the surroundings.

[1 mark] Temperature change of \(-5.6\ ^\circ\text{C}\) (allow a decrease of \(5.6\ ^\circ\text{C}\))
[1 mark] Endothermic
[1 mark] Correct reason (e.g., temperature decreased / energy was absorbed from the surroundings)

1. The overall energy change is calculated as: energy of products - energy of reactants = \(180\text{ kJ} - 320\text{ kJ} = -140\text{ kJ}\).
2. The reaction is exothermic because the products have less energy than the reactants, which shows that energy was released to the surroundings during the chemical reaction.

[1 mark] \(-140\text{ kJ}\) (allow a decrease/release of \(140\text{ kJ}\))
[1 mark] Exothermic
[1 mark] Products have less energy than reactants / energy is released to the surroundings

When the concentration of the hydrochloric acid is increased, there are more acid particles in the same volume of solution. This means the reactant particles are more crowded, leading to more frequent collisions (more collisions per second) between the particles. As a result, the rate of reaction increases.

[1 mark] More particles in a given volume (or particles are closer together / more crowded)
[1 mark] More frequent collisions (do not accept 'more collisions' on its own without a time reference like 'per second' or 'frequent')
[1 mark] Increased rate of reaction

A catalyst increases the rate of a chemical reaction without being used up itself. It does this by providing an alternative reaction pathway that has a lower activation energy, meaning more particles have the minimum energy required to react when they collide.

[1 mark] Increases the rate of reaction / speeds up the reaction
[1 mark] Provides an alternative pathway / route
[1 mark] Lower activation energy

First, the crude oil is heated and vaporised before entering the fractionating column. The column has a temperature gradient (it is hot at the bottom and cooler at the top). As the hydrocarbon vapours rise up the column, they cool. Different hydrocarbons have different boiling points, so they condense back into liquids at different heights and are tapped off as separate fractions.

[1 mark] Crude oil is heated and vaporised
[1 mark] Column has a temperature gradient / is hotter at the bottom and cooler at the top
[1 mark] Hydrocarbons condense at different heights / temperatures because they have different boiling points

1. 'N' represents nitrogen, and 'K' represents potassium.
2. When crops grow, they absorb essential mineral nutrients from the soil. When these crops are harvested, the nutrients are removed from the field. Applying fertilisers replaces these lost mineral ions so that subsequent crops have enough nutrients to grow healthily.

[1 mark] Nitrogen (for N) and Potassium (for K) (both must be correct for the mark)
[1 mark] Crops absorb nutrients/minerals from the soil which are lost when harvested
[1 mark] Fertilisers replace these lost elements/nutrients to sustain future crop growth / maintain soil fertility

The four main stages of a Life Cycle Assessment are:
1. Extracting and processing raw materials,
2. Manufacturing and packaging,
3. Use and operation during its lifetime,
4. Disposal at the end of its useful life (including transport and distribution at each stage).
Any three of these stages are required for full marks.

[3 marks] 1 mark for each correct stage listed (up to a maximum of 3):
- Extracting and processing raw materials
- Manufacturing and packaging
- Use and operation (during its lifetime)
- Disposal (at the end of its useful life, including transport)

Recycling aluminium is highly beneficial because:
1. It saves a significant amount of energy, as melting recycled aluminium requires much less energy than extracting it via electrolysis.
2. It conserves finite natural resources (bauxite ore).
3. It reduces environmental impacts like habitat destruction and pollution caused by mining, and reduces the amount of waste sent to landfill sites.

[3 marks] 1 mark for each valid reason listed (up to a maximum of 3):
- Saves energy / requires less electricity
- Conserves resources / bauxite ore
- Reduces mining / habitat destruction / quarrying
- Reduces carbon emissions / greenhouse gases
- Reduces waste sent to landfill
- Saves money / cheaper than extraction

1. To calculate the temperature change: \(21.0\text{ °C} - 14.5\text{ °C} = 6.5\text{ °C}\).
2. Since the temperature of the reaction mixture decreased, energy was absorbed from the surroundings.
3. This means the reaction is endothermic.

1 mark: Correct calculation of temperature change: 6.5 (°C).
1 mark: Identifying the reaction as endothermic.
1 mark: Giving the correct reason (e.g., because the temperature decreased / energy was taken in).

At a higher temperature, the reactant particles gain kinetic energy and move faster. This causes them to collide with each other more frequently. Additionally, more of the colliding particles have energy equal to or greater than the activation energy, leading to a higher proportion of successful collisions per second.

1 mark: Reactant particles gain kinetic energy / move faster.
1 mark: More frequent collisions (between particles).
1 mark: More successful collisions / more collisions have energy greater than or equal to the activation energy (allow: more energetic collisions).

In fractional distillation, the crude oil is first heated and vaporised. The vapour enters a fractionating column, which is hot at the bottom and becomes progressively cooler towards the top. As the vapours rise, the hydrocarbons condense back into liquids when they reach the level that matches their boiling point. Fractions with higher boiling points condense near the bottom, while those with lower boiling points condense near the top.

1 mark: Crude oil is heated and vaporised.
1 mark: The fractionating column is hotter at the bottom and cooler at the top (temperature gradient).
1 mark: Hydrocarbons / fractions condense at different levels / heights / temperatures (due to having different boiling points).

1. The nitrogen used in the Haber process is obtained directly from the air.
2. The hydrogen is typically sourced by reacting natural gas (methane) with steam.
3. Iron is used as a catalyst to increase the rate of the reaction without being used up.

1 mark: Nitrogen is obtained from the air.
1 mark: Hydrogen is obtained from natural gas / methane / steam / water.
1 mark: The catalyst used is iron (Fe).

A standard Life Cycle Assessment (LCA) evaluates four main stages:
1. Extracting and processing raw materials.
2. Manufacturing and packaging.
3. Use and operation during its lifetime.
4. Disposal at the end of its useful life (including transport and distribution at each stage).

Award 1 mark for each correct stage listed, up to a maximum of 3 marks:
- Extracting and processing raw materials
- Manufacturing and packaging
- Use and operation (during its lifetime)
- Disposal / end of life (including transport and distribution at each stage)

In an exothermic reaction, energy is released to the surroundings. Therefore, the products must have less chemical energy than the reactants. On a reaction profile, the horizontal line representing the products is drawn lower than the line for the reactants, and the overall energy change arrow points downwards (indicating a negative value).

1 mark: The products are at a lower energy level than the reactants (or reactants are higher than products).
1 mark: Energy is released / given out to the surroundings.
1 mark: The overall energy change is negative / the arrow for overall energy change points downwards.

1. To calculate the mean rate of reaction: \(\text{Rate} = \frac{\text{Volume of gas collected}}{\text{Time taken}} = \frac{40\text{ cm}^3}{20\text{ s}} = 2.0\text{ cm}^3\text{/s}\).
2. As the reaction proceeds, reactant particles are used up to form products.
3. This decrease in concentration of reactants results in fewer reacting particles per unit volume, which reduces the frequency of successful collisions.

1 mark: Correct calculation of mean rate: 2.0 (cm³/s).
1 mark: Reactants are used up / concentration of reactants decreases.
1 mark: Collision frequency decreases / fewer successful collisions per second.

1. During complete combustion, a hydrocarbon fuel reacts fully with oxygen to produce carbon dioxide and water. The word equation is: propane + oxygen → carbon dioxide + water.
2. Incomplete combustion occurs when there is a limited supply of oxygen. This leads to the formation of carbon monoxide (a highly toxic, colourless, and odourless gas) instead of carbon dioxide.

1 mark: Left-hand side of word equation: propane + oxygen.
1 mark: Right-hand side of word equation: carbon dioxide + water.
1 mark: Identifies carbon monoxide (CO) as the toxic pollutant gas (accept soot / carbon particulate only if qualified as a pollutant, but reject if not described as a gas).

In an endothermic reaction, energy is absorbed or taken in from the surroundings, which causes the temperature of the surroundings to decrease. Because energy is taken in, the chemical energy of the products is higher than the chemical energy of the reactants.

1 mark: State that energy is taken in / absorbed from the surroundings.
1 mark: State that the products have more energy than the reactants (or reactants have less energy than products).
1 mark: Link the temperature decrease of the mixture to energy being transferred from the surroundings.

For a substance to conduct electricity, it must contain charged particles that are free to move. In solid sodium chloride, the ions are held in fixed positions within a giant lattice by strong electrostatic forces and cannot move. When melted (molten), these forces are overcome, so the ions are free to move and carry electrical charge.

1 mark: State that in solid sodium chloride, ions are in fixed positions / cannot move.
1 mark: State that in molten sodium chloride, the ions are free to move.
1 mark: Explain that these moving ions are required to carry the electrical charge.

During thermal decomposition, calcium carbonate breaks down to produce calcium oxide solid and carbon dioxide gas. Because the reaction is carried out in an open test tube, the carbon dioxide gas escapes into the atmosphere, causing the remaining mass of solid to decrease. According to the conservation of mass, the mass of the escaped gas is the difference between the starting mass and the mass of the remaining solid: \(10.0\text{ g} - 5.6\text{ g} = 4.4\text{ g}\).

1 mark: Identify that carbon dioxide is a gas which escapes from the open test tube.
1 mark: Show a correct subtraction method: \(10.0\text{ g} - 5.6\text{ g}\).
1 mark: Provide the correct final mass: \(4.4\text{ g}\).

No reaction occurs between copper and zinc sulfate because copper is lower in the reactivity series than zinc, so it cannot displace it. Conversely, zinc is more reactive than copper. If zinc is added to copper sulfate solution, a displacement reaction occurs. The zinc displaces the copper, resulting in the formation of zinc sulfate solution and a reddish-brown solid deposit of copper metal.

1 mark: Explain that copper is less reactive than zinc (or cannot displace zinc).
1 mark: State that zinc is more reactive than copper.
1 mark: Describe that a displacement reaction occurs / copper is formed / the blue solution fades / a brown solid is produced.

1. Use a measuring cylinder to measure a fixed volume (e.g. 25 cm3) of dilute hydrochloric acid. 2. Pour the acid into a polystyrene cup and place the cup inside a beaker to make it stable. 3. Put a thermometer into the acid and record the initial temperature. 4. Weigh out a fixed mass of the first metal (e.g. magnesium) using a digital balance. 5. Add the metal to the acid in the polystyrene cup, quickly put a lid on the cup, and stir the mixture gently. 6. Look at the thermometer and record the maximum (highest) temperature reached. 7. Calculate the temperature change by subtracting the initial temperature from the maximum temperature. 8. Repeat the entire procedure using the exact same volume and concentration of acid, and the same mass of the other metals (zinc and iron).

Level 3 (5-6 marks): A detailed and coherent method is described. The steps are presented in a logical order, showing clearly how the apparatus is used to make accurate measurements. Key control variables are identified to ensure a fair test. Level 2 (3-4 marks): A simple method is described. Most of the steps are in a logical order, and some measurements and apparatus are identified. There is some mention of how to make it a fair test. Level 1 (1-2 marks): Isolated points are made. Some apparatus, measurements, or variables are mentioned but without a clear, logical sequence. Indicative content: Apparatus: polystyrene cup (to reduce heat loss), thermometer, measuring cylinder, beaker (for stability), lid, balance. Measurements: volume of acid, initial temperature of acid, maximum temperature of mixture, mass of metal. Calculation: temperature change = maximum temperature - initial temperature. Fair test controls: same volume of acid, same concentration of acid, same mass of metal, same starting temperature of acid, same state of division (particle size) of metal.

Increasing temperature increases the kinetic energy of the particles. This means they move faster, resulting in more frequent collisions, and a higher proportion of collisions have energy greater than or equal to the activation energy.

1 mark for the correct answer C. No marks for incorrect options.

Fractions collected at the top of the column contain smaller hydrocarbon molecules with shorter chains. These have lower boiling points, lower viscosity, and are easier to ignite.

1 mark for the correct answer B. No marks for incorrect options.

Hydrogen for the Haber process is obtained by reacting natural gas (methane) with steam, while nitrogen is obtained from the air.

1 mark for the correct answer C. No marks for incorrect options.

A Life Cycle Assessment (LCA) evaluates the environmental impacts of extracting raw materials, manufacturing and packaging, use and operation during its lifetime, and disposal at the end of its useful life.

1 mark for the correct answer C. No marks for incorrect options.

An endothermic reaction absorbs heat energy from the surroundings, which causes the temperature of the surroundings and the mixture to decrease.

1 mark for the correct answer B. No marks for incorrect options.

A catalyst provides an alternative pathway with a lower activation energy, allowing more reactant particles to have sufficient energy to successfully collide and react.

1 mark for the correct answer B. No marks for incorrect options.

Complete combustion occurs when there is plenty of oxygen, reacting with the hydrocarbon to produce carbon dioxide \(CO_2\) and water \(H_2O\).

1 mark for the correct answer C. No marks for incorrect options.

Potable water is water that is safe to drink. It is not completely pure chemically, as it still contains low concentrations of safe dissolved salts and minerals, but must have safe levels of microbes and dissolved salts.

1 mark for the correct answer C. No marks for incorrect options.

Decreasing the temperature reduces the kinetic energy of the particles. As a result, the particles collide less frequently and with less energy, which decreases the rate of reaction.

1 mark for correct choice C.

Fractional distillation is the industrial process used to separate hydrocarbons in crude oil into fractions of similar chain lengths and boiling points.

1 mark for correct choice B.

Methane is a greenhouse gas that absorbs infrared radiation and contributes to global warming. Nitrogen, oxygen, and argon do not act as greenhouse gases.

1 mark for correct choice B.

The first stage is passing the water through filter beds (filtration) to remove large insoluble materials and suspended solids.

1 mark for correct choice B.

Recycling aluminium uses significantly less energy (about 5%) compared to the energy-intensive process of electrolysis used to extract aluminium from bauxite ore.

1 mark for correct choice A.

In paper chromatography, the paper is the stationary phase because it does not move during the process, while the solvent is the mobile phase.

1 mark for correct choice C.

At dynamic equilibrium, the rate of the forward reaction is exactly equal to the rate of the reverse reaction, so the concentrations of reactants and products remain constant.

1 mark for correct choice C.

Sulfur impurities burn in oxygen to form sulfur dioxide gas, which dissolves in water droplets in clouds to produce acid rain.

1 mark for correct choice B.

Using larger lumps of calcium carbonate decreases the surface area available for the reaction. A smaller surface area results in fewer collisions between reactant particles per second, which decreases the rate of reaction.

1 mark for selecting the correct option (C). Accept 'c'.

Fractions with smaller hydrocarbon molecules have lower boiling points, are less viscous (more runny), and are highly flammable (easier to ignite) compared to fractions with larger molecules.

1 mark for selecting the correct option (C). Accept 'c'.

A Life Cycle Assessment (LCA) is used to evaluate environmental impacts throughout a product's life. The retail price of the product is an economic factor and is not part of an environmental LCA.

1 mark for selecting the correct option (B). Accept 'b'.

Methane, carbon dioxide, and water vapor are greenhouse gases. Nitrogen, oxygen, and argon are the main components of the atmosphere but are not greenhouse gases.

1 mark for selecting the correct option (D). Accept 'd'.

The nitrogen used in the Haber process is obtained from the air, and the hydrogen is obtained from natural gas (which contains methane).

1 mark for selecting the correct option (A). Accept 'a'.

1. Increasing concentration increases the rate of reaction. 2. There are more reactant particles in a given volume or space. 3. This leads to a higher frequency of collisions / more successful collisions per second.

1 mark: identifies that the rate of reaction increases. 1 mark: states that there are more particles in the same volume / space. 1 mark: explains that this results in more frequent successful collisions (or more collisions per second).

First, convert the time from minutes to seconds: \(3.0\text{ minutes} = 3.0 \times 60 = 180\text{ seconds}\). Next, calculate the mean rate of reaction: \(\text{Mean rate} = \frac{\text{volume of gas}}{\text{time}} = \frac{45\text{ cm}^3}{180\text{ s}} = 0.25\text{ cm}^3/\text{s}\).

1 mark: converts time to seconds: \(3.0 \times 60 = 180\text{ s}\). 1 mark: shows correct calculation setup: \(\frac{45}{180}\). 1 mark: gives correct final value of 0.25.

The reaction is endothermic because the temperature decreases. Energy is absorbed/taken in from the surroundings, which results in a temperature decrease of the mixture and surroundings.

1 mark: identifies the reaction as endothermic. 1 mark: states that energy is taken in/absorbed from the surroundings. 1 mark: explains that this absorption of energy causes the temperature of the surroundings to decrease.

1. Measure the starting temperature of the hydrochloric acid and sodium hydroxide solutions before mixing. 2. Mix the solutions inside the polystyrene cup, place the lid on to reduce heat loss, and measure the maximum temperature reached. 3. If the temperature increases, the reaction is exothermic.

1 mark: measure initial/starting temperature of solutions. 1 mark: mix solutions in the polystyrene cup with lid and record final/maximum temperature. 1 mark: state that a temperature increase indicates an exothermic reaction.

As the size of the hydrocarbon molecule increases, the intermolecular forces become stronger, which increases the boiling point. In a fractional distillation column, it is cooler at the top and hotter at the bottom. Therefore, hydrocarbons with lower boiling points condense and are collected near the top, while those with higher boiling points condense and are collected near the bottom.

1 mark: states that larger molecules have higher boiling points (or smaller molecules have lower boiling points). 1 mark: states that hydrocarbons with low boiling points are collected near the top of the column. 1 mark: states that hydrocarbons with high boiling points are collected near the bottom of the column.

First, find the formula for hexane: for \(n = 6\), \(2n+2 = 2(6)+2 = 14\), so the formula is \(C_6H_{14}\). Complete combustion produces carbon dioxide and water. The balanced chemical equation is: \(2C_6H_{14} + 19O_2 \rightarrow 12CO_2 + 14H_2O\) (or \(C_6H_{14} + 9.5O_2 \rightarrow 6CO_2 + 7H_2O\)).

1 mark: correct molecular formula of hexane: \(C_6H_{14}\). 1 mark: correct products of complete combustion (\(CO_2\) and \(H_2O\)) in an equation. 1 mark: correctly balanced equation: \(2C_6H_{14} + 19O_2 \rightarrow 12CO_2 + 14H_2O\) (accept balanced equation using fractions, e.g., with \(9.5O_2\)).

The four main stages of a life cycle assessment are: 1. Extracting and processing raw materials. 2. Manufacturing and packaging. 3. Use and operation during its lifetime. 4. Disposal at the end of its useful life. Excluding the disposal stage leaves the first three stages.

1 mark: extracting and processing raw materials. 1 mark: manufacturing and packaging. 1 mark: use and operation during its lifetime. (Accept any order)

Nitrogen is obtained from the fractional distillation of liquid air. Hydrogen is obtained by reacting methane (from natural gas) with steam. The reaction is catalysed using iron.

1 mark: nitrogen source is air. 1 mark: hydrogen source is natural gas / methane (accept steam / water). 1 mark: catalyst is iron.

The reaction is exothermic because the temperature increased from \(20\ ^\circ\text{C}\) to \(48\ ^\circ\text{C}\) (an increase of \(28\ ^\circ\text{C}\)). In an exothermic reaction, heat energy is released/transferred to the surroundings, causing the temperature of the surroundings to rise.

1 mark: Exothermic.
1 mark: (Because) the temperature increases / goes up (by \(28\ ^\circ\text{C}\)).
1 mark: (Because) energy is transferred to the surroundings.

Increasing the temperature increases the rate of reaction. This is because the particles gain kinetic energy, meaning they move faster and collide more frequently. Also, more of the colliding particles have energy greater than or equal to the activation energy, so a higher proportion of collisions are successful.

1 mark: Rate of reaction increases.
1 mark: Particles have more kinetic energy / move faster, leading to more frequent collisions.
1 mark: More particles have the activation energy, leading to a higher proportion of successful collisions.

Crude oil is first heated and vaporised. The vapour is fed into a fractionating column which is hot at the bottom and cooler at the top. The hydrocarbons rise up the column and condense when they reach their boiling points, separating them into different fractions.

1 mark: Crude oil is heated to vaporise it.
1 mark: The column is hotter at the bottom and cooler at the top.
1 mark: Hydrocarbons condense at different heights/levels according to their boiling points.

A life cycle assessment (LCA) looks at all stages of a product's life. Any three of the following stages are assessed: 1) Extracting and processing raw materials, 2) Manufacturing and packaging, 3) Use and operation during its lifetime, 4) Disposal at the end of its useful life.

1 mark: Extracting / processing raw materials.
1 mark: Manufacturing and packaging.
1 mark: Use/operation of product OR disposal / recycling at the end of its life.

The two raw materials used to make ammonia are nitrogen and hydrogen. Nitrogen is obtained from the air. Hydrogen is obtained from natural gas (or methane / water).

1 mark: Nitrogen and hydrogen (both needed for mark).
1 mark: Nitrogen is obtained from the air.
1 mark: Hydrogen is obtained from natural gas / methane (accept: reacting methane with steam).

A catalyst increases the rate of reaction. It does this by providing an alternative reaction pathway that has a lower activation energy. This means more particles have enough energy to react when they collide.

1 mark: Increases the rate of reaction (accept: speeds up the reaction).
1 mark: Provides an alternative reaction pathway.
1 mark: (The alternative pathway) has a lower activation energy.

In an endothermic reaction, the energy level of the products is higher than the energy level of the reactants. The profile shows a curve that rises from the reactants to a maximum peak (representing the activation energy) before falling slightly to the products. The activation energy is shown as an upward arrow from the reactant energy level to the peak of the curve.

1 mark: Products have higher energy than reactants.
1 mark: Curve rises to a peak / maximum before descending to the products.
1 mark: Activation energy is shown as the height difference between the reactants and the peak of the curve.

Alkanes have the general formula \(C_nH_{2n+2}\). The alkane with three carbon atoms is propane. Using the general formula where \(n=3\), the chemical formula of propane is \(C_3H_8\).

1 mark: \(C_nH_{2n+2}\).
1 mark: Propane.
1 mark: \(C_3H_8\) (accept standard non-subscripted text if clear, but formula must be correct).

Temperature change = \(18.5\ ^\circ\text{C} - 11.2\ ^\circ\text{C} = 7.3\ ^\circ\text{C}\). The reaction is endothermic because the temperature of the reaction mixture decreases, showing that energy is absorbed from the surroundings.

1 mark for calculating the temperature change: \(7.3\ ^\circ\text{C}\) (allow \(-7.3\ ^\circ\text{C}\)). 1 mark for identifying the reaction as endothermic. 1 mark for the reason: temperature decreases (or energy/heat is taken in from the surroundings).

1. In an exothermic reaction, the products have less energy than the reactants.
2. Energy is released (transferred) to the surroundings.
3. This causes the temperature of the surroundings to increase.

1 mark for stating that the products have less energy than the reactants (or energy of reactants is higher).
1 mark for stating that energy is released or transferred to the surroundings.
1 mark for stating that the temperature of the surroundings increases.

Mean rate of reaction = \(\frac{\text{volume of gas produced}}{\text{time taken}}\)
Mean rate = \(\frac{45\text{ cm}^3}{30\text{ s}} = 1.5\text{ cm}^3/\text{s}\)

1 mark for correct substitution of values: \(\frac{45}{30}\).
1 mark for the correct calculation: \(1.5\).
1 mark for the correct unit: \(\text{cm}^3/\text{s}\) (or \(\text{cm}^3\text{ s}^{-1}\)).

When the temperature is increased, the reacting particles gain kinetic energy and move faster. This results in more frequent collisions between the particles. Additionally, a greater proportion of the collisions have energy equal to or greater than the activation energy, leading to more successful collisions per second.

1 mark for stating that particles gain kinetic energy / move faster.
1 mark for stating that collisions are more frequent (accept 'more collisions per second', do not accept just 'more collisions').
1 mark for stating that more of the collisions have energy greater than or equal to the activation energy (or a higher proportion of collisions are successful).

As the size of the hydrocarbon molecules increases, the intermolecular forces become stronger. This leads to: 1. An increase in boiling point. 2. An increase in viscosity (the liquid becomes thicker and flows less easily). 3. A decrease in flammability (the substance becomes harder to ignite).

1 mark for stating that boiling point increases.
1 mark for stating that viscosity increases (or it gets thicker / flows less easily).
1 mark for stating that flammability decreases (or it gets harder to ignite / burn).

In complete combustion, propane reacts with oxygen to produce carbon dioxide and water:
\(\text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}\)

1 mark for identifying the correct reactants and products: \(\text{C}_3\text{H}_8 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\).
1 mark for balancing the carbon and hydrogen atoms: \(3\text{CO}_2\) and \(4\text{H}_2\text{O}\).
1 mark for balancing the oxygen atoms: \(5\text{O}_2\).

1. Nitrogen is obtained from the air. Hydrogen is obtained from natural gas (methane) reacting with steam.
2. The catalyst used in the Haber process is iron.

1 mark for stating that nitrogen is obtained from air.
1 mark for stating that hydrogen is obtained from natural gas/methane (accept steam/water).
1 mark for identifying iron as the catalyst.

The stages of a product's life cycle assessed in an LCA are:
1. Extracting and processing raw materials.
2. Manufacturing and packaging.
3. Use and operation during its lifetime.
4. Disposal at the end of its useful life, including transport and distribution at each stage.

Award 1 mark for each of any three of the following stages (up to a maximum of 3 marks):
- Extracting and processing raw materials.
- Manufacturing and packaging.
- Use and operation / maintenance during its lifetime.
- Disposal / recycling at the end of its useful life.

An excellent answer will compare both products across the four stages of a Life Cycle Assessment (LCA):

1. Extracting and processing raw materials:
- Plastic cups are made from crude oil, which is a non-renewable (finite) resource. Processing crude oil (fractional distillation, cracking, polymerisation) requires significant energy.
- Ceramic mugs are made from clay, which is a finite but abundant resource. Digging up clay (quarrying) can destroy habitats and cause noise/dust pollution.

2. Manufacturing and packaging:
- Plastic cups require relatively little energy to shape and manufacture per individual cup.
- Ceramic mugs require very high amounts of energy because they must be fired in a high-temperature kiln.

3. Use and operation:
- Plastic cups are single-use; they do not need washing, so no water or detergent is used during their short lifetime.
- Ceramic mugs are used hundreds or thousands of times. However, they must be washed regularly using hot water and detergent, which uses energy and can release chemicals into the environment.

4. Disposal:
- Plastic cups are disposed of after one use. They do not biodegrade, leading to landfill accumulation, or they are incinerated, which releases carbon dioxide. They can sometimes be recycled, but often are not.
- Ceramic mugs last a very long time. When broken, they are sent to landfill (they do not biodegrade) but because one mug replaces thousands of plastic cups, the total volume of waste is much lower.

Conclusion:
- Overall, the ceramic mug is more environmentally friendly if it is reused many times, as this offsets the high energy used in its manufacture and washing, and significantly reduces plastic waste.

Level 3 (5-6 marks):
A detailed and coherent evaluation is given, comparing both products across all or most of the four stages of the LCA. A clear, logical conclusion is made with supporting evidence.

Level 2 (3-4 marks):
A logical comparison is attempted, covering at least two stages of the LCA for both products, or a detailed description of most stages is given for only one of the products. A simple conclusion may be present.

Level 1 (1-2 marks):
Simple, isolated statements are made about the environmental impacts or stages of the LCA for one or both products. No coherent comparison or conclusion is made.

Level 0 (0 marks):
No relevant content.

Indicative content:
- Plastic: crude oil (finite), ceramic: clay (abundant/quarried).
- Plastic: low energy to make, ceramic: high energy (kiln firing).
- Plastic: single-use (no washing), ceramic: reusable (requires washing with energy, water, detergent).
- Plastic: landfill (slow to biodegrade) or incinerated, ceramic: landfill but much lower volume over time due to durability.
- Conclusion: Reusable ceramic is better if used many times to offset initial manufacturing footprint.