MetadataPastPaper.sampleTitle

A hydrocarbon molecule \(X\) is cracked to produce one molecule of propene and one molecule of butane. What is the molecular formula of \(X\) and what color change is observed when propene is bubbled into aqueous bromine?

Copper(II) sulfate is prepared by reacting excess copper(II) carbonate with dilute sulfuric acid. Which sequence of experimental steps produces a pure, dry sample of copper(II) sulfate crystals from the reaction mixture?

Which statement correctly describes the role of the placenta and the umbilical cord during human development?

An experiment was carried out to investigate the effect of pH on the rate of an enzyme-controlled reaction. At pH 2, the rate of reaction was high. At pH 8, no product was formed. When the enzyme was returned to pH 2 from pH 8, still no product was formed. Which statement explains these observations?

A circuit contains a \(12\text{ V}\) power supply connected to a network of resistors. The network consists of two \(6.0\ \Omega\) resistors connected in parallel with each other. This parallel combination is connected in series with a \(5.0\ \Omega\) resistor. What is the total current drawn from the power supply?

The list shows some of the events that occur in a lake after untreated sewage or fertilizer runoff enters the water: 1. Increased growth of producers (algal bloom). 2. Algae block light from reaching plants deeper in the water. 3. Under-surface plants die. 4. [Event X]. 5. Concentration of dissolved oxygen decreases. 6. Aquatic animals die. Which process is represented by [Event X]?

Which statement correctly describes the properties of electromagnetic waves?

Which statement correctly compares aerobic and anaerobic respiration in humans?

An object of mass 4.0 kg is pulled along a friction-free horizontal surface by a constant horizontal force of 12 N. The object starts from rest. What is the kinetic energy of the object after it has travelled a distance of 5.0 m?

Which statement about the reaction of ethene with bromine is correct?

An enzyme-catalysed reaction is investigated at different temperatures. Which statement correctly describes the effect of temperature on the enzyme and its activity?

A student wants to prepare a pure, dry sample of the insoluble salt, barium sulfate. Which pair of aqueous solutions should be mixed together to obtain barium sulfate as a precipitate?

A resistor of resistance \(R\) is connected in series with a parallel combination of two identical resistors, each of resistance \(R\). The total resistance of this combined circuit is \(12\ \Omega\). What is the value of \(R\)?

Which row correctly identifies the products of anaerobic respiration in yeast and in human muscle cells?

During the electrolysis of concentrated aqueous sodium chloride (brine) using inert electrodes, what are the primary products formed at the positive electrode (anode) and the negative electrode (cathode)?

A water wave travels from deep water into shallow water. What happens to its speed, frequency, and wavelength as it enters the shallow water?

An experiment was carried out to investigate the effect of temperature on the rate of an enzyme-controlled reaction. The rate of reaction increased from \(10^\circ\text{C}\) to \(40^\circ\text{C}\), but then fell rapidly above \(45^\circ\text{C}\). Which statement explains why the rate of reaction decreased above \(45^\circ\text{C}\)?

Hydrocarbon X is cracked to produce propene and hydrocarbon Y. One molecule of X produces exactly one molecule of propene and one molecule of Y. If the relative molecular mass (\(M_r\)) of X is 114, and Y is an alkane, which formula represents Y? (Ar: C = 12, H = 1)

A student wants to prepare a pure, dry sample of the insoluble salt, silver chloride (\(\text{AgCl}\)). Which pair of aqueous solutions should be mixed together to prepare this salt, and which method should be used to obtain the dry solid from the mixture?

Which statement correctly compares asexual and sexual reproduction?

Two identical resistors of resistance \(R\) are connected in series with a cell of electromotive force (e.m.f.) \(V\) and negligible internal resistance. The current in the circuit is \(I_s\). The two resistors are then reconnected in parallel across the same cell, and the current from the cell is now \(I_p\). What is the ratio \(\frac{I_p}{I_s}\)?

Which sequence of events shows the correct order during the eutrophication of a body of water after fertilizer runoff?

Which statement about electromagnetic waves is correct?

A scientist compares the processes of aerobic and anaerobic respiration in yeast cells. Which statement correctly describes a difference between these two processes?

An amylase enzyme catalyzes the breakdown of starch into maltose. A student measures the rate of this reaction at different temperatures. Which statement correctly explains why the rate of reaction decreases above the optimum temperature of \(40^\circ\text{C}\)?

A crane lifts a load of mass \(400\text{ kg}\) vertically upwards through a height of \(15\text{ m}\) in a time of \(30\text{ s}\). The acceleration of free fall, \(g\), is \(10\text{ m/s}^2\). What is the useful average power developed by the crane?

Hydrocarbon X reacts with aqueous bromine, turning it from orange to colorless. Hydrocarbon X also undergoes polymerization to form a long-chain molecule. Which statement about hydrocarbon X and its polymer is correct?

A student wants to prepare a pure, dry sample of the insoluble salt, barium sulfate (\(\text{BaSO}_4\)). Which pair of aqueous solutions should be mixed together to obtain a precipitate of barium sulfate?

A cell of electromotive force (e.m.f.) \(6.0\text{ V}\) is connected to a resistor of resistance \(12\,\Omega\). A charge of \(30\text{ C}\) passes through the resistor. How much energy is transferred to the resistor?

A species of plant produces flowers with large, feathery stigmas that hang outside the flower, small green petals, and large quantities of light, smooth pollen grains. Which method of pollination is this flower adapted for, and what is the function of its feathery stigmas?

Molten lead(II) bromide is electrolyzed using inert carbon electrodes. Which statement describes the correct observations at the electrodes?

Which statement correctly compares radio waves and gamma rays traveling in a vacuum?

A student investigates the effect of temperature on the rate of an amylase-catalyzed reaction. The time taken for starch to be completely broken down is measured at various temperatures: at \(20^\circ\text{C}\) it takes 10 minutes, at \(30^\circ\text{C}\) it takes 5 minutes, at \(40^\circ\text{C}\) it takes 2 minutes, at \(50^\circ\text{C}\) it takes 8 minutes, and at \(60^\circ\text{C}\) starch is still present after 30 minutes. Which statement best explains the result at \(60^\circ\text{C}\)?

Which row correctly describes the pollen grain and where fertilisation occurs in a wind-pollinated flower?

An organic compound \(X\) reacts with steam in the presence of an acid catalyst at high temperature and pressure to form ethanol. What is compound \(X\), and what type of reaction is this?

To prepare a pure, dry sample of soluble copper(II) sulfate crystals, a student adds excess copper(II) oxide to warm dilute sulfuric acid. Which sequence of steps should the student perform next to obtain the crystals?

Three identical \(6.0\ \Omega\) resistors are connected in a circuit. Two of the resistors are connected in parallel with each other, and this combination is connected in series with the third resistor and a \(9.0\text{ V}\) d.c. power supply of negligible internal resistance. What is the total current drawn from the power supply?

An electric motor is used to lift a load of \(40\text{ kg}\) vertically through a height of \(15\text{ m}\) in a time of \(6.0\text{ s}\). The acceleration of free fall, \(g\), is \(10\text{ m/s}^2\). Assuming the motor is \(80\%\) efficient, what is the electrical power input to the motor?

Concentrated aqueous sodium chloride is electrolysed using inert carbon electrodes. Which row correctly identifies the products formed at the anode and the cathode, and the change in pH of the electrolyte?

Which statement about electromagnetic waves is correct?

A toy car of mass \(0.5\text{ kg}\) is released from rest at the top of a smooth slope, which is at a vertical height of \(1.2\text{ m}\).

(a) Calculate the gravitational potential energy of the car at the top of the slope. (Take \(g = 9.8\text{ m/s}^2\)) [2]

(b) The car reaches the bottom of the slope. If \(15\%\) of the initial potential energy is lost as thermal energy due to friction, calculate the kinetic energy of the car at the bottom of the slope. [2]

(c) Calculate the speed of the car at the bottom of the slope. [3]

(d) Describe the difference between speed and velocity. [3]

Ethane, \(C_2H_6\), and ethene, \(C_2H_4\), are hydrocarbons.

(a) (i) Explain why ethene is described as an unsaturated hydrocarbon. [2]
(ii) Describe a chemical test to distinguish between ethane and ethene. Give the results for each compound. [3]

(b) Ethene can be polymerized to form poly(ethene).
(i) Draw the structure of poly(ethene) showing two repeat units. [2]
(ii) State the type of polymerization that occurs when poly(ethene) is formed. [1]

(c) Large alkane molecules can be cracked to produce smaller, more useful molecules. Write a balanced chemical equation for the cracking of decane, \(C_{10}H_{22}\), to produce oct-1-ene, \(C_8H_{16}\), and one other product. [2]

Enzymes are biological catalysts that speed up metabolic reactions.

(a) Explain how enzymes function in terms of the active site, substrate, and complementary shape (the lock and key model). [3]

(b) An experiment was carried out to study the rate of reaction of amylase at different temperatures.
(i) Describe and explain the effect of increasing the temperature from \(20^\circ\text{C}\) to \(40^\circ\text{C}\) on the rate of reaction. [3]
(ii) Describe and explain the effect of increasing the temperature above \(60^\circ\text{C}\) on the rate of reaction. [4]

A student prepares a sample of copper(II) sulfate crystals by reacting dilute sulfuric acid with copper(II) oxide.

(a) (i) Write a balanced chemical equation for this reaction. [2]
(ii) State why copper(II) oxide is added in excess. [1]
(iii) Describe how the excess copper(II) oxide is removed from the mixture. [1]
(iv) Describe how dry crystals of copper(II) sulfate are obtained from the resulting solution. [3]

(b) Explain, in terms of ions, the difference between a strong acid and a weak acid. [3]

An electrical circuit consists of a \(12\text{ V}\) d.c. power supply, a \(6.0\ \Omega\) resistor, and a \(12.0\ \Omega\) resistor connected in parallel.

(a) (i) Calculate the combined resistance of the two resistors in parallel. [2]
(ii) Calculate the total current drawn from the power supply. [2]
(iii) Calculate the electrical power dissipated in the \(6.0\ \Omega\) resistor. [3]

(b) Explain how the resistance of a thermistor changes as temperature increases, and describe how this property can be utilized in an automatic heating controller. [3]

Plant reproduction can occur sexually through pollination.

(a) Define pollination. [2]

(b) Compare insect-pollinated and wind-pollinated flowers in terms of:
(i) the appearance and structure of the petals, [2]
(ii) the structure and position of the anthers and stigma. [4]

(c) Describe the process of fertilization in a flowering plant, starting from the pollination of the stigma. [2]

Electrolysis is the breakdown of an ionic compound by the passage of electricity.

(a) Concentrated aqueous sodium chloride is electrolysed using inert carbon electrodes.
(i) Identify the product formed at the anode and the product formed at the cathode. [2]
(ii) Write the ionic half-equation for the reaction occurring at the anode. [2]
(iii) Explain why the solution becomes alkaline as the electrolysis proceeds. [2]

(b) Describe how a copper key can be electroplated with nickel. In your answer, specify:
- the electrolyte used
- the material used for the anode (+)
- the material used for the cathode (-)
- the ionic half-equation at the cathode. [4]

A ray of light in air is incident on the flat surface of a glass block at an angle of incidence of \(40^\circ\). The refractive index of the glass is \(1.5\).

(a) (i) Calculate the angle of refraction in the glass. [3]
(ii) State what happens to the speed of the light wave as it enters the glass block. [1]

(b) (i) State two properties that are common to all electromagnetic waves. [2]
(ii) Name the component of the electromagnetic spectrum that has the longest wavelength. [1]

(c) Describe one hazard and one safety precaution associated with exposure to ultraviolet (UV) radiation. [3]

A test car of mass \(800\text{ kg}\) is traveling along a straight horizontal track.

(a) Describe the difference between a scalar quantity, such as speed, and a vector quantity, such as velocity. [2]

(b) The car starts from rest and accelerates uniformly to a speed of \(15\text{ m/s}\) in a time of \(6.0\text{ s}\).

(i) Calculate the acceleration of the car. Show your working and state the unit. [2]

(ii) Calculate the kinetic energy of the car when it is traveling at \(15\text{ m/s}\). [2]

(c) After \(6.0\text{ s}\), the car travels at a constant speed of \(15\text{ m/s}\) for a further \(10\text{ s}\). During this time, the engine exerts a forward force of \(1200\text{ N}\).

(i) Calculate the work done by the engine during this \(10\text{ s}\) interval. [2]

(ii) Explain, in terms of forces, why the car travels at a constant speed even though the engine is exerting a forward force of \(1200\text{ N}\). [2]

(a) Define the term enzyme. [2]

(b) Describe how an enzyme catalyzes a reaction, with reference to the active site and the 'lock and key' hypothesis. [3]

(c) An experiment was conducted to study the effect of temperature on the rate of an amylase-catalyzed reaction.

(i) Explain why the rate of reaction is very low or zero when the enzyme is incubated at \(60^\circ\text{C}\). Use the term denatured in your answer. [3]

(ii) Explain why the rate of reaction decreases when the temperature is lowered from the optimum temperature of \(37^\circ\text{C}\) to \(10^\circ\text{C}\). [2]

A student investigates the electrolysis of concentrated aqueous copper(II) sulfate using inert carbon (graphite) electrodes.

(a) Describe what is observed at:

(i) the anode (positive electrode) [1]

(ii) the cathode (negative electrode) [1]

(iii) the electrolyte solution as the reaction proceeds. [1]

(b) Write ionic half-equations, including state symbols, for the reaction occurring at:

(i) the anode [2]

(ii) the cathode [2]

(c) The carbon electrodes are now replaced with copper electrodes.

(i) Describe the change in mass of the copper anode. [1]

(ii) Explain why the blue color of the electrolyte does not fade during this electrolysis. [2]

Hydrocarbons are organic compounds containing only hydrogen and carbon.

(a) Decane, \(\text{C}_{10}\text{H}_{22}\), is an alkane. It can be cracked to produce ethene, \(\text{C}_2\text{H}_4\), and another hydrocarbon, \(X\).

(i) Write a balanced chemical equation for the cracking of decane to produce ethene and hydrocarbon \(X\). State the molecular formula of \(X\). [2]

(ii) Describe a chemical test to distinguish between decane and ethene. Give the observation for each compound. [3]

(b) Ethene undergoes addition polymerization to form poly(ethene).

(i) Draw the structure of the monomer, ethene, showing all atoms and bonds. [1]

(ii) Draw a diagram to represent a section of poly(ethene) showing two repeating units. [2]

(iii) Poly(ethene) is non-biodegradable. State two environmental problems caused by the disposal of non-biodegradable plastics in the environment. [2]

A student investigates the effect of pH on the activity of amylase. Amylase breaks down starch. In five separate test-tubes, amylase is mixed with starch solution and a buffer solution of a specific pH. Every 30 seconds, a sample from each mixture is added to a drop of iodine solution on a white tile. The time taken for the starch to be completely broken down is measured. (a) Identify: (i) the independent variable. [1] (ii) the dependent variable. [1] (b) At pH 7, the student records that the blue-black color of iodine no longer appears after 2 minutes and 30 seconds. (i) Convert this time into seconds. [1] (ii) State the final color of the iodine mixture when starch has been completely broken down. [1] (c) Explain why the test-tubes containing the amylase and starch solutions are placed in a water bath at 35 degrees Celsius for 5 minutes before mixing them. [2] (d) Explain why a water bath is used to maintain the temperature instead of directly heating the test-tubes with a Bunsen burner. [2] (e) Describe a control experiment that the student could perform to prove that the breakdown of starch is catalyzed by the active enzyme amylase. [2]

A student investigates the temperature change when different masses of sodium hydrogen carbonate are added to 25 cubic centimeters of dilute hydrochloric acid in a polystyrene cup. The initial temperature of the acid is measured. The sodium hydrogen carbonate is added, the mixture is stirred, and the lowest temperature reached is recorded. (a) For one mass, the initial temperature of the acid was 21.5 degrees Celsius. The lowest temperature recorded was 14.5 degrees Celsius. (i) Calculate the temperature change. [1] (ii) State whether this reaction is exothermic or endothermic, and justify your answer. [2] (b) State two reasons why a polystyrene cup is used in this experiment instead of a glass beaker. [2] (c) Identify two variables that must be kept constant in this investigation to ensure a fair test. [2] (d) Describe how the student could measure the 25 cubic centimeters of dilute hydrochloric acid as accurately as possible. [1] (e) Suggest one safety hazard in this experiment and describe a suitable precaution to minimize the risk. [2]

A student investigates the relationship between the length of a simple pendulum, l, and its period of oscillation, T. The student sets up a pendulum suspended from a clamp stand. (a) The student measures the length of the pendulum l from the bottom of the support clamp to the center of the pendulum bob. On a diagram, a ruler shows the bottom of the clamp is at 0.0 cm and the center of the bob is at 75.5 cm. (i) State the length of the pendulum in meters. [1] (ii) State one precaution the student must take when using a ruler to measure this length to avoid a parallax error. [1] (b) The student displaces the bob slightly, releases it, and measures the time taken for 20 complete oscillations. (i) The stopwatch shows a time of 34.80 seconds. Calculate the period T of one oscillation. [1] (ii) Calculate the value of T squared. [1] (c) Explain why measuring the time for 20 oscillations and dividing by 20 is more accurate than measuring the time for only 1 oscillation. [2] (d) A student repeats the procedure for several lengths, plots a graph of T squared on the y-axis against length l on the x-axis, and draws a straight line of best fit through the origin. (i) The gradient of the line is calculated to be 4.02 seconds squared per meter. Using the equation \( g = \frac{4\pi^2}{\text{gradient}} \), calculate the value of the acceleration of free fall, g. Show your working. Use \( \pi = 3.142 \). [2] (ii) State one adjustment the student could make to the pendulum setup to ensure the oscillations remain in a single plane and do not wobble. [2]

A student investigates the fermentation of glucose solution by yeast at different temperatures. A mixture of glucose solution and yeast is placed in a test-tube connected by a delivery tube to a gas syringe. (a) After 10 minutes at 35 degrees Celsius, the gas syringe shows that 48.0 cubic centimeters of gas has been collected. (i) State the name of this gas. [1] (ii) Describe a chemical test, including the positive observation, to confirm the identity of this gas. [2] (b) State the observation when the liquid mixture from the test-tube is filtered and tested with: (i) aqueous bromine. [1] (ii) acidified potassium manganate(VII) with gentle heating. [2] (c) To determine the concentration of ethanoic acid formed as a side-product in the mixture, the student titrates a 10.0 cubic centimeter sample of the filtered reaction mixture against 0.10 mol/dm3 sodium hydroxide solution using phenolphthalein indicator. (i) State the color change of the indicator at the end-point. [2] (ii) Suggest why the student must filter the mixture before performing the titration. [2]

A student investigates how the resistance of a wire depends on its length. The student sets up a circuit to measure the current in the wire and the potential difference across a length of the wire. (a) Draw a circuit diagram containing a cell, a switch, an ammeter, a voltmeter, and a length of resistance wire. The ammeter must measure the current through the resistance wire, and the voltmeter must measure the potential difference across the resistance wire. [3] (b) For a wire length of 50.0 cm, the student records: - Current, I = 0.45 A - Potential difference, V = 1.80 V (i) Calculate the resistance, R, of this 50.0 cm length of wire. State the unit. [2] (ii) Predict the resistance of a 100.0 cm length of the same wire, assuming resistance is directly proportional to length. [1] (c) State one reason why the switch should be opened between taking readings. [1] (d) The student notices that the wire becomes very hot during the experiment. (i) State one safety hazard associated with this. [1] (ii) Suggest one improvement to the method to prevent the wire from becoming too hot. [2]

A student investigates the rate of respiration in germinating mung bean seeds using a simple respirometer. The apparatus consists of a test-tube containing the germinating seeds supported on a wire mesh. Below the mesh, there is a chemical that absorbs carbon dioxide. The test-tube is sealed with a rubber bung containing a capillary tube with a small drop of red dye. (a) State the name of a chemical that can be used to absorb carbon dioxide in this experiment. [1] (b) Explain why the drop of red dye moves along the capillary tube towards the test-tube containing the seeds. [3] (c) The student measures the position of the dye every minute for 5 minutes. The results are: - At 0 minutes: 10 mm - At 1 minute: 18 mm - At 2 minutes: 27 mm - At 3 minutes: 35 mm - At 4 minutes: 44 mm - At 5 minutes: 52 mm (i) Calculate the distance moved by the dye in 5 minutes. [1] (ii) Calculate the average rate of movement of the dye in mm/min. [1] (d) Describe a control experiment that should be carried out to prove that the movement of the dye is due to respiration by the living seeds, and not due to changes in environmental temperature or pressure. [2] (e) State one environmental factor that must be kept constant during this experiment, and explain why it must be kept constant. [2]