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Four potato cylinders of equal initial length are placed in four different test-tubes, each containing a different concentration of sucrose solution. After two hours, the change in length of each cylinder is measured. Which concentration of sucrose solution is closest to the concentration of the cell sap inside the potato cells?

Which statement about alkanes and alkenes is correct?

Which row correctly describes the differences between evaporation and boiling of liquid water?

A car travels along a straight road. It accelerates uniformly from rest to a speed of 15 m/s in 5 s, then travels at a constant speed of 15 m/s for 10 s, and finally decelerates uniformly to rest in a further 5 s. What is the total distance travelled by the car?

Which row correctly describes the structural features of arteries compared to veins?

A plant is grown in a culture solution deficient in magnesium ions. Which symptom will this plant show, and what is the reason for this?

Which statement about the electromagnetic spectrum is correct?

A student performs a paper chromatography experiment to identify a dye. The solvent front moves 8.0 cm from the baseline. The spot of the dye moves 6.0 cm from the baseline. What is the \(R_f\) value of this dye?

A plant cell is placed in a concentrated salt solution. Which row correctly describes what happens to the vacuole and the cell membrane?

Which row correctly describes the relative thickness of the muscular wall of the right ventricle compared to the left ventricle, and the relative oxygen concentration of the deoxygenated blood in the pulmonary artery?

An aqueous solution of an unknown salt is tested. Adding aqueous sodium hydroxide produces a green precipitate that is insoluble in excess. Adding dilute nitric acid followed by aqueous barium nitrate produces a white precipitate. What is the identity of the salt?

Which statement correctly describes a property or reaction of hydrocarbons?

A student sits near the side of a hot metal canister filled with boiling water. The student feels thermal energy transferring to their hand, even though they are not touching the canister. Which processes are primarily responsible for transferring thermal energy through the metal wall of the canister, and then through the air to the student's hand at the side?

A wooden box of mass \(4.0\text{ kg}\) is pushed along a horizontal wooden floor by a constant force of \(18\text{ N}\). A frictional force of \(6.0\text{ N}\) acts in the opposite direction to the motion. What is the acceleration of the box?

Chlorine, bromine, and iodine are elements in Group VII of the Periodic Table. Which statement about the trends or properties of these elements is correct?

Which statement about the properties of electromagnetic waves is correct?

Identical cylinders of potato tissue are placed into four different test-tubes, each containing a different concentration of sucrose solution. In which test-tube will the potato cylinder show the greatest percentage increase in mass?

Which row correctly describes the relative wall thickness, lumen diameter, and the presence of valves in a typical vein compared to a typical artery?

Which row correctly identifies the function of the palisade mesophyll cells and the guard cells in a leaf?

A student tests an unknown salt solution. The addition of aqueous sodium hydroxide produces a green precipitate that is insoluble in excess. Dilute nitric acid followed by aqueous barium nitrate is then added, which produces a white precipitate. What is the identity of the salt?

Which statement about the trends as we go down Group VII of the Periodic Table is correct?

A sample of a gaseous hydrocarbon is bubbled through aqueous bromine. The orange-brown bromine solution immediately becomes colorless. Which statement about the hydrocarbon is correct?

A hot metal block is suspended inside a vacuum chamber. By which method or methods of thermal energy transfer can energy leave the block and reach the walls of the chamber?

Which row correctly describes the speed of all electromagnetic waves in a vacuum, and how the wavelength of these waves changes from radio waves to gamma rays?

In a paper chromatography experiment, a student measures the distance from the baseline to the solvent front as 12.0 cm. A blue spot of food colouring travels 4.8 cm from the baseline. What is the Rf value of the blue food colouring?

A student has four identical flasks containing equal amounts of hot water at 80 degrees Celsius. Each flask has a different surface coating: Flask 1 is dull black, Flask 2 is shiny silver, Flask 3 is dull white, and Flask 4 is shiny white. The flasks are left to cool in a laboratory. Which flask will cool down the fastest, and which will cool down the slowest?

A toy car of mass 2.0 kg accelerates from rest to a speed of 6.0 m/s in a time of 3.0 s. What is the average useful power required to produce this acceleration?

Which option correctly describes the bonding in ethene and the change observed when it is shaken with aqueous bromine?

The characteristics of three blood vessels are described: Vessel X has a large lumen, a thin wall, and carries blood towards the heart. Vessel Y has a very small lumen (one cell wide), a wall one cell thick, and links arterioles to venules. Vessel Z has a small lumen, a thick muscular wall, and carries blood away from the heart. Which option correctly identifies vessels X, Y, and Z?

An experiment is set up to study osmosis in plant cells. Identical cylinders of potato are placed in salt solutions of different concentrations. In which solution will the plant cells become turgid, and what is the reason?

Which statement about the trends in the Group VII elements (the halogens) from chlorine to iodine is correct?

A radio wave travels at a speed of 3.0 x 10^8 m/s in a vacuum and has a frequency of 1.5 x 10^8 Hz. What is its wavelength, and how does its wavelength compare to that of visible light?

Four potato cylinders of equal initial mass are placed into four different sucrose solutions: P, Q, R, and S. After two hours, the percentage change in mass of each cylinder is measured: Cylinder in P = \(+8\%\), Cylinder in Q = \(-5\%\), Cylinder in R = \(0\%\), and Cylinder in S = \(+12\%\). Which solution has the highest water potential?

Which row correctly identifies the chamber of the heart that pumps blood to the lungs, and the blood vessel that carries oxygenated blood back to the heart?

A student performs a paper chromatography experiment to analyze a dye. The solvent front travels \(8.0\text{ cm}\) from the baseline. The spot of the dye travels \(6.0\text{ cm}\) from the baseline. What is the \(R_f\) value of the dye?

An organic compound X is a liquid that decolorizes aqueous bromine. When X undergoes complete combustion, it forms carbon dioxide and water. Which statement about X is correct?

A student investigates the rate of evaporation of water. She places equal volumes of water into four identical open containers under different environmental conditions. Which set of conditions will produce the fastest rate of evaporation?

An object starts from rest and accelerates uniformly to a speed of \(12\text{ m/s}\) in \(4.0\text{ s}\). It then travels at this constant speed of \(12\text{ m/s}\) for another \(6.0\text{ s}\). What is the total distance traveled by the object during these \(10.0\text{ s}\)?

Which statement correctly compares radio waves and gamma rays?

A wire of length \(L\) and cross-sectional area \(A\) has a resistance of \(8.0\\ \Omega\). A second wire made of the same metal has a length of \(2L\) and a cross-sectional area of \(2A\). What is the resistance of the second wire?

A student investigates a green solid, compound X.

(a) A solution of X is tested by adding a few drops of aqueous sodium hydroxide. A pale green precipitate forms which is insoluble in excess. State the name of the transition metal ion present in X. [1]

(b) Describe a chemical test, including the observation for a positive result, to confirm that compound X contains carbonate ions. [2]

(c) The student also performs paper chromatography on a food colouring containing three dyes. Explain why the baseline (start line) on the chromatogram must be drawn in pencil and not in ink. [2]

(d) Explain how the chromatogram can be used to determine if the food colouring is a pure substance or a mixture, and how the \(R_f\) value of a component is calculated. [3.88]

A student investigates the rate of evaporation of water from two different containers, A and B.

Container A is a wide, shallow dish with a large surface area of \(120\text{ cm}^2\). Container B is a tall, narrow beaker with a surface area of \(30\text{ cm}^2\). Both contain the same volume of water at \(40\text{ }^{\circ}\text{C}\).

(a) Explain, in terms of molecules, why evaporation causes the remaining water to cool down. [3]

(b) State and explain, in terms of molecules, which container will have a higher rate of evaporation. [2.88]

(c) The student wants to reduce the rate of heat loss from Container B. They decide to wrap the sides of the beaker in shiny aluminium foil.
Explain how wrapping the beaker in shiny aluminium foil reduces heat loss by radiation. [3]

A toy car of mass \(0.50\text{ kg}\) is pulled along a flat horizontal floor.

(a) Calculate the kinetic energy of the car when it is travelling at a constant speed of \(4.0\text{ m/s}\). State the formula used. [2.88]

(b) The car is then accelerated uniformly from rest to a speed of \(6.0\text{ m/s}\) in \(3.0\text{ seconds}\).
(i) Calculate the acceleration of the car. Show your working and state the unit. [3]
(ii) Calculate the force required to produce this acceleration. [3]

Petroleum is a mixture of hydrocarbons. It can be separated into fractions by fractional distillation.

(a) State the physical property on which fractional distillation depends. [1]

(b) Decane (\(\text{C}_{10}\text{H}_{22}\)) can be cracked to form octane (\(\text{C}_8\text{H}_{18}\)) and ethene (\(\text{C}_2\text{H}_4\)).
(i) Write a balanced chemical equation for this cracking reaction. [2]
(ii) Describe a chemical test to distinguish between octane and ethene. State the reagent used and the observation for each compound. [3.88]

(c) Ethene can react with steam to form ethanol. State the type of reaction that occurs and one essential condition for this process. [2]

The human circulatory system is responsible for the transport of blood.

(a) Describe the difference between the structure of an artery and the structure of a vein. Relate these differences to their functions. [3.88]

(b) Humans have a double circulation system.
(i) Explain what is meant by the term 'double circulation'. [2]
(ii) State one advantage of a double circulation system. [1]

(c) State the name of the blood vessel that carries oxygenated blood from the lungs to the left atrium of the heart, and the valve that prevents blood from flowing back into this atrium from the ventricle. [2]

An experiment is carried out using potato cylinders to study osmosis.

Two potato cylinders of equal size and mass are placed in different solutions for two hours:
- Cylinder A is placed in distilled water.
- Cylinder B is placed in a concentrated sucrose solution.

(a) Define the term osmosis. [3]

(b) Explain, in terms of water potential, why cylinder A increases in mass, while cylinder B decreases in mass. [3.88]

(c) Plant cells do not burst when placed in distilled water, whereas red blood cells would. State the part of the plant cell that prevents it from bursting. [2]

Group I of the Periodic Table contains the alkali metals.

(a) State the trend in reactivity of the alkali metals as you go down Group I. Explain this trend in terms of the arrangement of electrons. [3.88]

(b) Sodium reacts vigorously with water.
(i) State two observations that would be made during this reaction. [2]
(ii) Write a balanced chemical equation for the reaction of sodium with water, including state symbols. [3]

Photosynthesis is the process by which plants manufacture carbohydrates.

(a) Write the balanced chemical equation for photosynthesis. [3]

(b) The leaf is adapted to carry out photosynthesis efficiently.
(i) Explain how the palisade mesophyll layer is adapted for maximum photosynthesis. [2.88]
(ii) Describe how carbon dioxide enters the leaf and reaches the palisade cells. [3]

A student investigates how different surfaces absorb thermal radiation. Both cans are placed at an equal distance from a powerful infrared heater. Can X is painted matt black. Can Y is painted shiny silver. Each contains identical volumes of cold water. (a) State the principal method of thermal energy transfer from the infrared heater to the cans through the air. [1] (b) Explain, in terms of particles (including electrons), how thermal energy is conducted through the copper walls of the cans. [3] (c) (i) State and explain which can, X or Y, will show a greater rise in water temperature after 10 minutes. [2] (ii) Copper has a high thermal conductivity. State how this property affects the rate of heat transfer to the water compared to using a plastic can. [1] (d) A lid is placed on each can. Explain how this lid reduces thermal energy loss by convection. [2]

A student is investigating a solid sample, salt **X**, which is a mixture of two salts.

They perform several tests and record their observations.

(a) The student dissolves salt **X** in distilled water to make solution **Y**. They divide this solution into three portions.

(i) To the first portion, they add dilute nitric acid followed by aqueous silver nitrate. A cream-coloured precipitate is formed.
Identify the anion present in salt **X**. [1]

(ii) To the second portion, they add aqueous sodium hydroxide dropwise until in excess. A green precipitate is formed which remains insoluble in excess.
Identify the cation present in salt **X**. [1]

(iii) Write down the chemical name of the compound formed from the anion identified in (a)(i) and the cation identified in (a)(ii). [1]

(b) To the third portion, the student adds dilute hydrochloric acid and warms gently. They test the gas evolved using filter paper soaked in acidified potassium manganate(VII).
The purple filter paper turns colourless.

(i) State the name of the gas evolved. [1]

(ii) Identify the other anion present in salt **X**. [1]

(c) The student wants to obtain a pure, dry sample of the green precipitate formed in (a)(ii) from the mixture.
Describe the experimental steps they should take to obtain this pure, dry solid. [3]

(d) Another student suggests using a flame test to check if sodium ions are also present in salt **X**.

(i) Describe how to perform a flame test. [1]

(ii) State the expected observation if sodium ions are present. [1]

A student investigates how the material of a beaker affects the rate of cooling of hot water.

They use two beakers of identical size and shape: Beaker A is made of copper, and Beaker B is made of glass.

(a) Describe how the student should set up the apparatus and carry out the experiment. State the measurements they should make and the apparatus used to make them. [4]

(b) Suggest two variables that must be kept constant to ensure a fair comparison. [2]

(c) The table below shows the temperature of water in Beaker B (glass) at 60-second intervals.

| Time / s | Temperature / °C |
|---|---|
| 0 | 85.0 |
| 60 | 76.5 |
| 120 | 69.5 |
| 180 | 63.5 |
| 240 | 58.5 |
| 300 | 54.0 |

(i) Calculate the average rate of cooling over the first 120 seconds. Include the unit in your final answer. [2]

(ii) State how the rate of cooling changes as time progresses, and explain this observation in terms of temperature difference. [2]

A student investigates the effect of light intensity on the rate of photosynthesis of an aquatic plant, *Elodea* (cabomba/pondweed).

The student sets up the apparatus with a light source at a distance \(d\) from the plant and counts the number of gas bubbles produced per minute.

(a) Draw a labelled diagram of the apparatus that could be used for this investigation. [3]

(b) Suggest why the student adds a small amount of sodium hydrogencarbonate to the water. [1]

(c) The student records the following data:

| Distance \(d\) / cm | Number of bubbles in minute 1 | Number of bubbles in minute 2 | Average number of bubbles per minute |
|---|---|---|---|
| 10 | 48 | 50 | 49 |
| 20 | 35 | 33 | 34 |
| 30 | 21 | 19 | 20 |
| 40 | 11 | 9 | 10 |
| 50 | 5 | 3 | 4 |

(i) State the independent variable and the dependent variable in this experiment. [2]

(ii) Describe the relationship shown by the data between the distance \(d\) and the average rate of bubble production. [1]

(iii) State how the light intensity changes as the distance \(d\) increases. [1]

(d) Explain why counting the number of bubbles may not be an accurate method to measure the volume of gas produced, and suggest one way to improve the accuracy of this measurement. [2]

A student investigates osmosis using potato cylinders.

They prepare five potato cylinders of equal length and diameter. They record the initial mass of each cylinder and then place each into a different concentration of sucrose solution: 0.0, 0.2, 0.4, 0.6, and 0.8 mol/dm³.

After 2 hours, they remove the potato cylinders, gently dry them, and measure their final mass.

Their results are shown in the table below:

| Concentration of sucrose / mol/dm³ | Initial mass / g | Final mass / g | Percentage change in mass / % |
|---|---|---|---|
| 0.0 | 4.24 | 4.62 | +8.96 |
| 0.2 | 4.15 | 4.31 | +3.86 |
| 0.4 | 4.30 | 4.13 | -3.95 |
| 0.6 | 4.08 | 3.75 | -8.09 |
| 0.8 | 4.21 | 3.72 | **(i)** |

(a)
(i) Calculate the percentage change in mass for the potato cylinder placed in 0.8 mol/dm³ sucrose solution. Show your working. Give your answer to two decimal places. [2]

(ii) Explain why the potato cylinder in 0.0 mol/dm³ sucrose solution gained mass. [2]

(b) Describe how the student should dry the potato cylinders before weighing them and explain why this step is necessary. [2]

(c) State why percentage change in mass is calculated rather than just using the actual change in mass. [1]

(d) Explain how the concentration of sucrose inside the potato cells can be determined from a graph of percentage change in mass against sucrose concentration. [2]

(e) Suggest one safety precaution the student should take when preparing the potato cylinders. [1]