Cambridge A Level Physical Science 8780 — 2014 Oct/Nov Paper 2 · Variant 1

1 Units can be expressed with a prefix which changes the size of the unit. Table 1.1 gives some examples. Table 1.1 prefix symbol power of ten centi c 10–2 10–6 M giga Complete the table. [3]

Mark scheme: 1 prefix symbol power of ten centi C 10–2 micro µ 10–6 [1] mega M 106 [1] giga G 109 [1] [3] award 1 mark for each correct row

2 Briefly describe how iron obtained from a blast furnace is purified before it is made into steel. .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[2]

Mark scheme: 2 any two from: [2] iron is melted/molten and treated with magnesium to remove sulphur oxygen blown through to oxidise carbon and phosphorus limestone added to remove the acidic oxides [2]

3 Fig. 3.1 shows a circuit diagram. The battery of electromotive force 12 V and negligible internal resistance, is used to light a filament lamp. When switch S is closed, the current initially rises to a peak before decreasing to a steady value. S A Fig. 3.1 Explain why the current rises to a peak and then decreases. .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[2]

Mark scheme: 3 idea that the filament is cool and takes time to warm up [1] resistance of metals increases with (increasing) temperature [1] [2]

4 An alkane burns completely in oxygen. The resulting gaseous mixture contains seven times as many moles of carbon dioxide as there were moles of the alkane. Write a balanced chemical equation for this combustion reaction. ......................................................................................................................................................[2]

Mark scheme: 4 C7H16 + 11O2 → 7CO2 + 8H2O (allow multiples/fractions) C7H16 [1] balanced equation [1] [2]

5 A sound wave passes through a medium. Fig. 5.1 shows the displacement of particles in the medium at a given moment in time. Fig. 5.2 shows the displacement of particles in the same medium as the sound wave passes a point. displacement 0 0 0.5 1.0 1.5 2.0 position / m Fig. 5.1 displacement 0 0 2.0 4.0 6.0 8.0 time / ms Fig. 5.2 (a) Determine the wavelength of the sound wave. wavelength = .......................................................m [1] (b) Determine the frequency of the sound wave. frequency = .................................................... Hz [2] (c) Determine the speed of the sound wave through the medium. speed = ................................................. m s–1 [1]

Mark scheme: 5 (a) 1.3 (m) [1] (b) T = 4.0 ms [1] (f =1/4.0 × 10–3) = 250 (Hz) [1] for ecf it must be a clearly expressed value of T (c) 325 (m s–1) ecf from (a) and (b) [1] [4]

6 When chlorine is bubbled into dilute sodium hydroxide, a solution containing sodium chlorate(I) is formed. This is a redox reaction. Cl2 + 2NaOH NaCl + NaCl O + H2O (a) Deduce the oxidising agent and the reducing agent in this reaction. Explain your answers in terms of changes in oxidation numbers. oxidising agent .......................................................................................................................... explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... reducing agent .......................................................................................................................... explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... [3] (b) When sodium chlorate(I) reacts with hydrogen peroxide, oxygen gas is produced. Balance the equation for this reaction. ........... NaClO + ........... H2O2 ........... NaOH + ........... Cl2 + ........... O2 [1]

Mark scheme: 6 (a) chlorine quoted as both oxidising and reducing agents [1] reducing agent = chlorine, as oxidation state goes from 0 to +1 [1] oxidising agent = chlorine as oxidation state goes from 0 to –1 [1] allow 1 mark for correctly deducing oxidation states or correctly deducing oxidising and reducing behaviour from incorrect oxidation states (b) 2NaCl O + H2O2 → 2NaOH + Cl2 + O2 allow multiples / fractions [1] [4]

7 (a) Define electric field strength. ................................................................................................................................................... ...............................................................................................................................................[1] (b) Fig. 7.1 shows the path of a β-particle as it moves in a uniform electric field. electric `-particle field Fig. 7.1 (i) Complete Fig. 7.2 to show the path that a proton, travelling at a similar speed to the β-particle, would take in the same electric field. [2] electric proton field Fig. 7.2 (ii) Complete Fig. 7.3 to show the path that a neutron, travelling at a similar speed to the β-particle, would take in the same electric field. [1] electric neutron field Fig. 7.3

Mark scheme: 7 (a) (electric field strength =) (electric) force on a (stationary) unit positive charge [1] (b) (i) curved upwards within field [1] good curve and significantly less deflection than beta e.g. hits plate in last 1/3 of plate [1] (ii) no deflection [1] [4]

8 Consider the reaction scheme below. H CH3 CH3 H CH3 CH3 C C CH3 CH2 CH C CH3 CH3 C C CH3 + Z Br CH3 CH3 OH CH3 W X Y (a) Briefly describe how compound W can be converted into compound X. ................................................................................................................................................... ...............................................................................................................................................[1] (b) Give the systematic name for compound X. ...............................................................................................................................................[1] (c) Compound Z is a structural isomer of Y. Draw the structural formula of Z. [1]

Mark scheme: 8 (a) (hot) KOH dissolved in alcohol [1] (b) 3,3-dimethylbut-1-ene [1] (c) structure for 3,3-dimethylbutan-1-ol [1] [3]

9 Fig. 9.1 shows a satellite orbiting the Moon in a circular orbit. satellite Moon orbital path Fig. 9.1 (a) Draw an arrow on Fig. 9.1 to show the direction of the resultant force on the satellite. [1] (b) Explain why the work done by the satellite as it orbits is zero. ................................................................................................................................................... ...............................................................................................................................................[1]

Mark scheme: 9 (a) arrow pointing towards the centre of the circle (Moon) [1] (b) force is (always) perpendicular to the (direction of) motion / displacement in one orbit = 0 [1] [2]

10 (a) Draw a dot-and-cross diagram to show the outer electrons in a molecule of NH3. [1] (b) Ammonia reacts with oxygen to produce nitrogen monoxide. 4NH3 + 5O2 4NO + 6H2O ΔH = –900 kJ mol–1 Use this equation, and data from the Data Booklet, to determine a value for the bond energy in a nitrogen monoxide molecule. bond energy in NO = ............................................ kJ mol–1 [3]

Mark scheme: 10 (a) diagram showing three single covalent bonds and one lone pair on N [1] (b) extracts correct bond energy data for N–H, O=O, O–H [1] –900 = 7160 – (5520 + 4b.e.) [1] (4b.e. = 2540) b.e. = 635 [1] [4] [Total: 30]