Isotopes — Paper 3 · IGCSE Sciences - Co-ordinated (Double) 0654

11 (a) A house has solar panels fitted on the roof. State one disadvantage of generating electricity from solar energy. … … [1] (b) Fig. 11.1 shows a hot water storage tank in the house. hot water out tank water electric heater cold water in Fig. 11.1 Complete the sentence below. The electric heater is placed near the bottom of the tank so that all the water can be heated by the process of … . [1] (c) The house is fitted with a smoke detector. The smoke detector contains a radioactive isotope of americium-241, which emits α-particles. (i) State the meaning of the term isotope. … … … [1] (ii) State the composition of α-particles. … … [1] (iii) α-particles are ionising radiation. Explain why ionising radiation is hazardous. … … … [2] (iv) Suggest why the α-particle source poses little or no danger to people passing by the smoke detector. … … [1] (d) Fig. 11.2 shows a woman standing in front of a mirror mounted on a wall in the house. mirror Fig. 11.2 Describe the image formed in the mirror by choosing three words or phrases from the list below. laterally inverted magnified not upside down real same size smaller upside down virtual 1 … 2 … 3 … [2]

9 marks

Mark scheme: 11(a) doesn’t work at night / when there is little light ; 1 11(b) convection ; 1 11(c)(i) atoms of the same element that have same proton number but different neutron number etc. ; 1 11(c)(ii) 2p + 2n / helium nucleus ; 1 11(c)(iii) ionises atoms / molecules in cells ; causes mutation / cancer ; 2 11(c)(iv) alpha particles are absorbed by 5cm of air ; 1 11(d) laterally inverted same size not upside down virtual one correct one mark ; all three correct two marks ; 2

This question in 0654/33 May/June 2017

4 (a) A radioactive isotope of iodine is used by a doctor to examine the thyroid gland of a patient. The patient takes a tablet containing the iodine, which is absorbed by the thyroid gland. The iodine emits γ-rays, that are detected outside the body. (i) Name a suitable detector for γ-rays. … [1] (ii) State the meaning of the term isotope. … … [1] (b) α-particles, β-particles and γ-rays are ionising. (i) Place these three radiations in order of their ionising ability. … … … [1] most ionising least ionising (ii) State one effect of ionising radiation on the human body. … … [1] (c) Fig. 4.1 shows a special thermometer used in hospitals to take the temperature of babies. The temperature reading is produced using thermal radiation from the human body. Thermal radiation is part of the electromagnetic spectrum. SCAN Fig. 4.1 (i) Suggest the part of the electromagnetic spectrum used by this thermometer. … [1] (ii) Fig. 4.2 shows an incomplete electromagnetic spectrum. Add the part of the electromagnetic spectrum you have suggested in (c)(i) in the correct place in Fig. 4.2. γ -rays ultraviolet microwaves Fig. 4.2 [1] (d) Endoscopes are used by doctors to observe inside a patient. An endoscope uses optical fibres. Complete Fig. 4.3 to show how a ray of light travels down an optical fibre by total internal reflection. Fig. 4.3 [1]

7 marks

Mark scheme: 4 4( 4 4( 4 4( 4 Que (a)(i) solid s (a)(ii) existen (b)(i) (b)(ii) mutatio (c)(i) infra-re (c)(ii) infra-re 4(d) total in estion 14.5 (° state detector / S nce of an eleme α on of cells / canc ed ; ed in correct box nternal reflection ° C) ; SSD / GM tube / p nt that has atom β cer etc. ; x ; n at the wall of th photographic film ms with same pro γ ; he fibre througho m ; oton number but out the fibre ; Answer Infra-red t different neutro on number / mas ss number ; Ma 1 1 1 1 1 1 1 arks

This question in 0654/33 Oct/Nov 2017

2 (a) Fig. 2.1 shows the symbols of six elements and six statements about these elements. On Fig. 2.1 draw one straight line from each symbol to the correct statement. One line has already been drawn for you. symbol statement a halogen Al the metal obtained Ca from bauxite the metal combined F in limestone the element used to C make sulfuric acid the element in diamond K a very reactive metal S Fig. 2.1 [3] (b) The chemical symbols of an atom of beryllium and an atom of boron are shown in Fig. 2.2. nucleon number 9 11 Be B proton number 4 5 Fig. 2.2 Complete Table 2.1 to show the numbers of neutrons and electrons in these atoms. Table 2.1 neutrons electrons Be B [2] (c) Sodium and chlorine combine to form sodium chloride. Fig. 2.3 shows the electronic structure of an atom of sodium and of an atom of chlorine. sodium atom chlorine atom Fig. 2.3 Complete Fig. 2.4 to show the electronic structures of the ions that form from these atoms. sodium ion chloride ion Fig. 2.4 [2] (d) Fig. 2.5 shows apparatus a student uses to produce a neutral solution of sodium chloride. Apparatus F contains a dilute acid which is added slowly to an alkaline solution contained in the beaker. pH meter apparatus F pH dilute acid tap to allow acid to run out beaker alkaline solution Fig. 2.5 (i) Name apparatus F. … [1] (ii) State the alkaline solution and the dilute acid that react to produce sodium chloride. alkaline solution … dilute acid … [2] (iii) Suggest a value of the pH of the solution in the beaker before any acid is added. pH = … [1] [Total: 11]

11 marks

Mark scheme: 2(a) 1 correct ; 3 correct ;; 5 correct ;;; 3 2(b) n e Be 5 4 B 6 5 ;; 2 2(c) sodium ion correct ; chloride ion correct ; 2 2(d)(i) burette ; 1 Question Answer Marks 2(d)(ii) sodium hydroxide ; hydrochloric (acid) ; 2 2(d)(iii) >7 up to 14 ; 1

This question in 0654/33 Oct/Nov 2019

12 (a) Fig. 12.1 shows a circuit containing a battery of 4 cells. A2 A1 P V Q Fig. 12.1 (i) Name the components P and Q. component P … component Q … [2] (ii) The battery is a source of electromotive force (e.m.f.). State the unit of e.m.f. unit = … [1] (iii) The switch is closed and both lamps light up. Readings are recorded on ammeters A1 and A2. Describe the difference, if any, in the readings of A1 and A2. Explain your answer. difference … explanation … … [2] (b) Fig. 12.2 shows a mains operated d.c. power source. + AC-DC – transformer Fig. 12.2 Identify one electrical hazard on Fig. 12.2. … [1] (c) Argon gas is used in some types of lamp. An argon atom has the chemical symbol 41 8Ar.0 State the composition of the nucleus of an atom of Argon. … … … [2] (d) A sample of radioactive rock was tested to see if it emitted α-particles. (i) Describe how a radiation detector could be used to show that α-particles were being emitted. … … … … [2] (ii) When the sample of radioactive rock is removed from the detector, the detector continues to record some radiation. Explain this observation. … … [1] [Total: 11]

11 marks

Mark scheme: 12(a)(i) P – variable resistor; Q – voltmeter; 2 Question Answer Marks 12(a)(ii) volt; 1 12(a)(iii) ammeter 1 will be lower than ammeter 2; current from the source is larger than the current in each branch; 2 12(b) damaged cable, insulation damaged; 1 12(c) 18 protons ; 22 neutrons; 2 12(d)(i) counts recorded (without paper); put paper in front of sample to see if counts reduce ; 2 12(d)(ii) background radiation; 1

This question in 0654/31 May/June 2020

8 (a) Two isotopes of iron are iron-54 and iron-56. Both isotopes have a proton number of 26. Iron-54 has a nucleon number of 54 and iron-56 has a nucleon number of 56. (i) State the number of electrons in one atom of iron-54. … [1] (ii) Determine the difference in the number of neutrons between an atom of iron-54 and an atom of iron-56. … [1] (b) Iron is extracted from iron oxide using carbon monoxide. Carbon dioxide is also made. (i) Write the word equation for this reaction. + + [1] (ii) State the substance that is oxidised in this reaction. … [1] (c) Iron reacts with two other substances to make rust. (i) Name the element and the compound that react with iron when it rusts. element … compound … [2] (ii) Iron is coated with a material to prevent rusting. Suggest one suitable material to use. … [1] [Total: 7]

7 marks

Mark scheme: 8(a)(i) 26 ; 1 8(a)(ii) 2 ; 1 8(b)(i) iron oxide + carbon monoxide → iron + carbon dioxide ; 1 8(b)(ii) carbon monoxide ; 1 8(c)(i) (element) – oxygen ; (compound) – water ; 2 8(c)(ii) paint ; 1

This question in 0654/33 Oct/Nov 2021

5 (a) An isotope of magnesium has a proton number (atomic number) of 12 and a nucleon number (mass number) of 26. Complete Table 5.1 to show the numbers of neutrons and electrons in an atom of this isotope. Table 5.1 number of number of number of isotope protons neutrons electrons magnesium-26 12 [2] (b) Fig. 5.1 shows part of the reactivity series of metals. potassium sodium calcium magnesium aluminium increasing reactivity zinc iron copper Fig. 5.1 Magnesium reacts slowly with cold water. Use the reactivity series to predict the result when calcium reacts with cold water. Explain your answer. prediction … … explanation … … [2] (c) Magnesium reacts with carbon dioxide. Magnesium oxide and carbon are made. (i) Write the word equation for this reaction. + + [1] (ii) The reaction between magnesium and carbon dioxide is exothermic. State what is meant by the term exothermic. … … [1] (d) Platinum is a transition metal. Magnesium is not a transition metal. State two properties of platinum that are not properties of magnesium. 1 … 2 … [2] (e) Table 5.2 shows the composition of an alloy of magnesium. Table 5.2 element % by mass aluminium 6.0 calcium 2.0 magnesium manganese 0.4 zinc 0.1 Complete the table with the % by mass of magnesium. Calculate the mass of magnesium in 1.0 kg of the alloy. mass = … kg [2] [Total: 10]

10 marks

Mark scheme: 5(a) 2 isotope number of number of number of protons neutrons electrons magnesium-26 12 14; 12; 5(b) calcium reacts quickly/quicker ; 2 calcium is higher in reactivity series than magnesium ; 5(c)(i) magnesium + carbon dioxide → magnesium oxide + carbon ; 1 5(c)(ii) releases (thermal) energy ; 1 5(d) any two from: 2 forms coloured compounds ; acts as catalyst ; variable valency ; 5(e) 91.5 (%) ; 2 0.915 (kg) ;

This question in 0654/32 Oct/Nov 2022

11 (a) State the name given to mixtures made from a metal with other elements. … [1] (b) Iron is an element in Period 4 of the Periodic Table. State the name of the collection of metals in Period 4 that contains iron. … [1] (c) Describe the test used to identify iron(II) ions and give the observation for a positive result. test … … observation … … [2] (d) State the two substances that react with iron to make rust. 1 … 2 … [2] (e) An isotope of iron has a proton number of 26 and a nucleon number of 58. (i) Deduce the number of neutrons and the number of electrons in this isotope of iron. neutrons = … electrons = … [2] (ii) State the meaning of the term isotope. … … [1] (f) A teacher reacts dilute hydrochloric acid with four metals. The observations are shown in Table 11.1. Table 11.1 metal observation calcium bubbles quickly iron only a few bubbles lithium bubbles very quickly silver no bubbles Place the four metals in order of their reactivity from the most reactive to the least reactive. most reactive … … … least reactive … [2] [Total: 11]

11 marks

Mark scheme: 11(a) alloy ; 1 11(b) transition elements / metals ; 1 11(c) aqueous sodium hydroxide ; 2 green precipitate ; 11(d) oxygen ; 2 water ; 11(e)(i) neutrons = 32 ; 2 electrons = 26 ; 11(e)(ii) atoms of the same element that have different numbers of neutrons ; 1 11(f) lithium 2 calcium iron silver lithium and / or silver correct ; all else correct ;

This question in 0654/32 Feb/March 2023

3 (a) A spacecraft carrying an astronaut travels 384 000 km from the Earth to the Moon in 78 hours. Calculate the average speed of the spacecraft in km / s. average speed = … km / s [3] (b) The mass of the astronaut on the Earth is 90 kg. (i) Calculate the weight of the astronaut on the Earth. The gravitational force on unit mass, g, is 10 N / kg. weight = … N [2] (ii) State the mass of the astronaut on the Moon. mass = … kg [1] (c) (i) The astronaut communicates with Earth using radio waves. Fig. 3.1 shows an incomplete electromagnetic spectrum. Write radio waves in the correct position in Fig. 3.1. increasing frequency visible X-rays light Fig. 3.1 [1] (ii) Explain why it is not possible for the astronaut to communicate with Earth using sound waves. … … [1] (d) The astronaut collects a lump of moon rock. The rock contains iron-60, a radioactive isotope. (i) State the meaning of the term isotope. … … [1] (ii) Iron-60 decays by the emission of β-particles. Complete the sentences to describe the nature of β-particles. β-particles are identical in nature to … . β-particles have a single … charge. [2] [Total: 11]

11 marks

Mark scheme: 3(a) speed = distance / time (in any form) or 384 000 / 280 800 ; = 1.37 (km / s) ; 3 3(b)(i) weight = mass  g (in any form) or 90  10 ; = 900 (N) ; 2 3(b)(ii) 90 (kg) ; 1 3(c)(i) radio (waves) in right hand box ; 1 3(c)(ii) sound waves need a medium / sound waves do not travel through a vacuum ; 1 3(d)(i) atoms of the same element that have different numbers of neutrons ; OR atoms which have the same number of protons and different numbers of neutrons ; OR atoms which have the same atomic number but different mass number ; 1 Question Answer Marks 3(d)(ii) electrons ; negative ; 2

This question in 0654/33 May/June 2023

5 (a) Table 5.1 shows some information about three Group VII elements. Complete Table 5.1. Table 5.1 element formula of molecules colour metal or non-metal? bromine orange non-metal chlorine iodine I2 grey-black [3] (b) State the name given to the Group VII elements in the Periodic Table. … [1] (c) An atom of one of the isotopes of iodine contains 53 protons and 74 neutrons. Some statements about iodine are shown below. Place a tick (3) to show the correct statements about iodine. All iodine atoms contain 53 electrons. All iodine molecules contain 148 neutrons. The protons are found in the nucleus. The neutrons are found in the nucleus. [2] (d) Describe what is observed when aqueous silver nitrate is added to aqueous potassium chloride and to aqueous potassium bromide. aqueous potassium chloride … … aqueous potassium bromide … … [2] (e) A gas jar filled with air is placed on top of a gas jar filled with orange bromine vapour. After several hours, the bromine vapour has mixed with the air. This is shown in Fig. 5.1. gas jar air + bromine air gas jar bromine at start after several hours Fig. 5.1 Explain why the bromine mixes with the air. Use ideas about the movement of molecules in your answer. … … … … [2] [Total: 10]

10 marks

Mark scheme: 5(a) 3 formula of metal or non- element colour molecules metal? bromine Br2 orange non-metal chlorine Cl2 (pale) green non-metal iodine I2 grey-black non-metal one mark for each column ;;; 5(b) halogens ; 1 5(c)  2 no tick /    3 ticks and 3 correct = 2 marks 4 ticks and 3 correct = 1 mark 3 ticks and 2 correct = 1 mark 2 ticks and 2 correct = 1 mark ;; 5(d) potassium chloride – white precipitate ; 2 potassium bromide – cream/off white precipitate ; 5(e) diffusion ; 2 molecules move randomly from place to place / spread out / from high to low concentration ;

This question in 0654/33 Oct/Nov 2023

5 (a) Table 5.1 contains information about 6 atoms or ions A, B, C, D, E and F. Table 5.1 number of number of number of electronic atom or ion protons neutrons electrons configuration A 1 0 1 1 B 6 6 6 2.4 C 6 8 6 2.4 D 10 10 10 2.8 E 17 18 17 2.8.7 F 17 18 18 2.8.8 State the letter or letters that: (i) is an atom of hydrogen … [1] (ii) is in Group VII of the Periodic Table … [1] (iii) is a noble gas … [1] (iv) is an ion … [1] (v) are isotopes of the same element … and … . [1] (b) The melting point of hydrogen is –259 °C. The boiling point of hydrogen is –253 °C. Suggest a temperature at which hydrogen would be a liquid. temperature = … °C [1] (c) The temperature of a fixed volume of hydrogen gas is increased. State the effect of this increase on the pressure of the hydrogen gas. … [1] (d) State the chemical test for hydrogen gas. Give the positive result. test … result … [2] (e) Some water is made by reacting hydrogen gas with oxygen gas. Describe how to test for the purity of the water made by using boiling point information. … … [1] [Total: 10]

10 marks

Mark scheme: 5(a)(i) A ; 1 5(a)(ii) E ; 1 5(a)(iii) D ; 1 5(a)(iv) F ; 1 5(a)(v) B and C ; 1 5(b) between – 254 and – 258 °C ; 1 5(c) (pressure) increases ; 1 5(d) lighted splint ; 2 goes pop ; 5(e) pure water will boil at 100°C / ora ; 1

This question in 0654/31 May/June 2025

9 Table 9.1 shows data about six metals. Table 9.1 melting point boiling point density metal / °C / °C kg / m3 aluminium 660 2470 2700 iron 1538 2862 7900 lead 328 1749 11400 mercury –39 357 13500 tin 232 2602 7300 uranium 1132 4131 19100 (a) (i) Identify the metal in Table 9.1 that has the greatest density. … [1] (ii) Water has a density of 1000 kg / m3. Use data from Table 9.1 to explain why all the metals in Table 9.1 sink when placed in water. … … [1] (b) (i) Mercury is a liquid at room temperature (20 °C). Explain how Table 9.1 shows this. … … [1] (ii) Describe the structure of liquid mercury in terms of the arrangement and separation of the particles. arrangement … … separation … … [2] (iii) Describe how the motion of particles in liquid mercury changes as the temperature decreases. … … [1] (c) Uranium-238 has the nuclide notation 23 8 9 2U. Describe the composition of the nucleus of a uranium-238 atom. … … [2] (d) An alloy of lead and tin is used to make fuse wire. The alloy has a melting point of 200 °C. A fuse contains fuse wire and is used to protect electrical devices in electrical circuits. Describe how the fuse protects the electrical circuit from the heating effect of an electric current. … … … … [2] [Total: 10]

10 marks

Mark scheme: 9(a)(i) uranium ; 1 9(a)(ii) (all the metals) have a density greater than water / (all the metals) have a density greater than 1000 (kg / m3) ; 1 9(b)(i) melting point is below 20 °C and boiling point is above 20 °C ; 1 9(b)(ii) irregular / random ; 2 close together / most touching ; 9(b)(iii) (move) more slowly 1 9(c) 92 protons ; 2 146 neutrons ; 9(d) any two from: 2 • if too much current ; • fuse wire melts ; • breaks circuit ;

This question in 0654/31 Oct/Nov 2025