Physics Unit P2 Physics For Your Future'

Transcript

1 Physics Unit P2 Physics For Your Future' Study and Revision Pack (Foundation Paper) Content Page number P2 overview and assessment 2 tracking P2.1 Specification statements 3 P2.1 Exam Questions 5 P2.2 Specification statements 18 P2.2 Exam Questions 19 P2.3 Specification statements 29 P2.3 Exam Questions 31 P2.4 Specification statements P2.4 Exam Questions P2.5 Specification statements P2.5 Exam Questions P2.6 Specification statements P2.6 Exam Questions Name: Form: 1

2 Overview and assessment tracking Please use the table below to keep track of your revision. Revision complete? Questions completed? Marks in first try % in first try Marks in second try % in second try P2.1 P2.2 P2.3 P2.4 P2.5 P2.6 Use the grade boundaries below as a guide to the grade you are achieving: % Grade 90 A* 80 A 70 B 60 C 50 D <50 U 2

3 Topic 1: Static and Current Electricity Current RAG P2.1 Specification statements P2 Specification Revised Describe the structure of the atom, limited to the position, mass and charge of protons, neutrons and electrons 1.2 Explain how an insulator can be charged by friction, through the transfer of electrons 1.3 Explain how the material gaining electrons becomes negatively charged and the material losing electrons is left with an equal positive charge 1.4 Recall that like charges repel and unlike charges attract 1.5 Demonstrate an understanding of common electrostatic phenomena in terms of movement of electrons, including: a shocks from everyday objects b lightning c attraction by induction such as a charged balloon attracted to a wall and a charged comb picking up small pieces of paper 1.6 Explain how earthing removes excess charge by movement of electrons 1.7 Explain some of the uses of electrostatic charges in everyday situations, including paint and insecticide sprayers 1.8 Demonstrate an understanding of some of the dangers of electrostatic charges in everyday situations, including fuelling aircraft and tankers together with the use of earthing to prevent the build-up of charge and danger arising 1.9 Recall that an electric current is the rate of flow of charge 1.10 Recall that the current in metals is a flow of electrons 1.11 Use the equation: charge (coulomb, C) = current (ampere, A) time (second, s) Q = I t 1.12 Recall that cells and batteries supply direct current (d.c.) 1.13 Demonstrate an understanding that direct current (d.c.) is movement of charge in one direction only 3

4 P2.1 Exam Questions- 36 marks, 36 minutes. Questions Q1. An atom contains electrons, neutrons and protons. (a) Use words from the box to complete the sentences. (i) The charge on an electron is (ii) An electron has a mass that is (b) At a petrol station, a pipe is used to transfer petrol to the storage tanks. The pipe is earthed. There is friction between the petrol and the end of the pipe. (i) Explain why it is dangerous not to earth the pipe. (ii) Explain how earthing the pipe makes this process much safer. 4

5 *(c) The photographs show some electrostatic effects. Explain in terms of electric charges how one of these effects is caused. You may include diagrams to help with your answers. (6) (Total for Question is 12 marks) 5

6 Q2. (a) Vicky combs her hair with a plastic hair comb. The comb now has a negative charge. (i) Complete the sentence by putting a cross ( ) in the box next to your answer. The comb has a negative charge because it has A gained electrons B lost electrons C gained protons D lost protons (ii) Vicky's hair has also become charged. Explain how Vicky's hair has become charged. (iii) Vicky holds the comb over a small piece of metal foil. The foil jumps up and sticks to the comb. Show on the diagram where the foil is negatively charged. (b) Vicky combs her hair with a metal comb. Then she tries to pick up some small pieces of metal foil with the comb. The metal comb does not pick up any pieces of metal foil. Explain why the metal foil is not picked up by the comb. 6

7 (c) The picture shows an electrostatic paint sprayer about to be used to paint a metal object. When the paint particles leave the sprayer, they are negatively charged. Explain the benefits of using this sprayer compared with one that does not charge the paint. (6) (Total for Question is 12 marks) 7

8 Q3. Electrostatic discharge (a) Marie works in an office which has a nylon carpet. She walks across the carpet towards her filing cabinet. There is friction between her shoes and the carpet. When she touches the metal handle of her filing cabinet she feels an electric shock. (i) State the name of the charged particles which have been transferred between the carpet and her shoes. (ii) The following sentences explain how Marie got the electric shock. The sentences are in the wrong order. Put them in the correct order by numbering the boxes. Two have been done for you. actions order in which the actions happen Marie walks across the nylon carpet 1 charge flows from Marie to the filing cabinet Marie touches the handle 4 charge is transferred by friction on to Marie Marie has lost her negative charge a negative charge builds up on Marie (b) Marie has another filing cabinet which has a black conductive strip at the top. This black strip helps to prevent electric shocks. This strip has a high resistance but still conducts charge. If Marie touches the strip before touching the handle she does not feel a shock. Explain, using the idea of electric current, why Marie does not feel a shock. (3) 8

9 *(c) Sparks from electrostatic discharge can sometimes be very dangerous. They can cause a fire or an explosion. Safety precautions are taken to reduce risks. Explain how safety precautions, in a particular situation, reduce the risks of fire or explosion. You may draw a labelled diagram to help with your answer. (6) 9

10 Topic 2: Controlling and using electric current Current RAG Revised 1 Revised 2 Revised 3 P2.2 Specification statements P2 Specification 2.1 Describe how an ammeter is placed in series with a component to measure the current, in amps, in the component 2.2 Explain how current is conserved at a junction 2.3 Explain how the current in a circuit depends on the potential difference of the source 2.4 Describe how a voltmeter is placed in parallel with a component to measure the potential difference (voltage), in volts, across it 2.6 Investigate the relationship between potential difference (voltage), current and resistance 2.7 Explain how changing the resistance in a circuit changes the current and how this can be achieved using a variable resistor 2.8 Use the equation: potential difference (volt, V) = current (ampere, A) resistance (ohm, Ω) V = I R 2.9 Demonstrate an understanding of how current varies with potential difference for the following devices: a filament lamps b diodes c fixed resistors 2.15 Describe tests to show the following ions are present in solids or solutions: a Na+, K+, Ca2+, Cu2+ using flame tests b CO3 2- using dilute acid and identifying the carbon dioxide evolved c SO4 2- using dilute hydrochloric acid and barium chloride solution d Cl- using dilute nitric acid and silver nitrate solution 2.16 Recall that chemists use spectroscopy (a type of flame test) to detect the presence of very small amounts of elements and that this led to the discovery of new elements, including rubidium and caesium 10

11 P2.2 Exam Questions- 40 marks, 40 minutes Questions Q1. Using electrical heating Victor rides a motorbike. He buys a kit to heat its handlebars in winter. The kit has two handle bar grips. Each grip contains an electrical heating coil. (a) Complete the sentence by putting a cross ( ) in the box next to your answer. When the coils are switched on, they get hot because A current is lost in the coils B energy is transferred in the coils C resistance is transferred in the coils D atoms flow through the coils (b) The kit also has a three position switch and a 2.4 ohm resistor. The diagram shows how Victor connects the parts. 11

12 Victor wants to check the voltage of the battery. Add a meter to the diagram to show how to measure the battery voltage. (c) Victor moves the switch to the high heat position. The 12 V battery produces a current of 2.5 A in the circuit. (i) Calculate the electrical power produced. (ii) R = V / I Calculate the total resistance of the circuit. electrical power =... W total resistance =... Ω (d) Victor moves the switch to the low heat position. The grips do not get as hot. Explain why the grips are not as hot. (e) The 2.4 ohm resistor must be fixed somewhere on the motorbike frame where it cannot be touched by the rider. Suggest a reason why. Q2. An inventor is designing a battery-powered torch. She wants the torch to have a brightness control. (a) Which of these could she use in this control? Put a cross ( ) in the box next to your answer. A a diode B a light-dependent resistor C a thermistor D a variable resistor 12

13 (b) She builds this circuit to test the lamp in the torch. (i) Add a voltmeter to the circuit which will measure the potential difference (voltage) across the lamp. She sets the control at the "bright" position. The current is 0.26 A and the potential difference (voltage) across the lamp is 6.0 V. Calculate the resistance of the lamp. (c) The inventor takes readings of the potential difference (voltage) across the lamp and the current at different positions of the control from "dim" to "bright". She plots a graph of the readings. (i) Complete this graph by plotting the missing point and drawing the curve of best fit. (ii) Describe what this graph shows about how the current changes as the voltage changes. 13

14 (iii) The lamp gives no light when the brightness control is at its lowest setting. Suggest why the torch would still need an on/off switch as well as the brightness control. (Total for Question = 10 marks) Q3. (a) Some students investigate electric circuits. They set up this circuit. What can the students do to increase the brightness of the lamp? Put a cross ( ) in the box next to your answer. A add another lamp in series B add another lamp in parallel C increase the resistance of the variable resistor D decrease the resistance of the variable resistor (b) The students want to measure both the current in the lamp and the potential difference (voltage) across the lamp. (i) Complete the circuit below with an ammeter and a voltmeter correctly connected. The power supply, variable resistor and lamp symbols are already drawn for you. (3) (ii) The current in a lamp is 0.5 A. Its resistance is 8 Ω. Calculate the potential difference (voltage) across the lamp. (c) Some electrical energy is transferred to light energy in the lamp. Explain why only some of the electrical energy is transferred to light energy in the lamp. 14

15 (d) The students use a different lamp in the circuit. The current in this lamp is 0.4 A. The potential difference (voltage) across the lamp is 5 V. Calculate the power being supplied to the lamp. (Total for Question is 10 marks) Q4. A student sets up an experiment to measure the potential difference (voltage) across a filament lamp. She changes the current through the lamp. The diagram shows the circuit she used. (c) Complete the sentence by putting a cross ( (i) The component X in the circuit diagram is a A diode B fixed resistor C thermistor D variable resistor (ii) The meter that measures potential difference is ) in the box next to your answer. A in parallel with the power supply B in parallel with the lamp C in series with the lamp D in series with the component X (iii) Describe how the student should increase the current in the lamp. 15

16 (b) The student recorded these readings. current / A Four points are plotted on the graph. (i) Plot the points for 2.0 V and 8.0 V. (ii) Draw the line of best fit. potential difference / V (c) Calculate the resistance of the lamp when the current is 0.44 A and the potential difference is 10.0 V. (d) Describe the energy transfer that takes place in the lamp. resistance = Ω (Total for Question is 10 marks) 16

17 Topic 3: Covalent Compounds and Separation Techniques Current Revised RAG Revised 1 Revised 2 3 C2.3 Specification statements C2 Specification 3.1 Describe a covalent bond as a pair of electrons shared between two atoms 3.2 Recall that covalent bonding results in the formation of molecules 3.3 Explain the formation of simple molecular, covalent substances using dot and cross diagrams, including: a hydrogen b hydrogen chloride c water d methane 3.4 Classify different types of elements and compounds by investigating their melting points and boiling points, solubility in water and electrical conductivity (as solids and in solution) including sodium chloride, magnesium sulfate, hexane, liquid paraffin, silicon(iv) oxide, copper sulfate, and sucrose (sugar) 3.5 Describe the properties of typical simple molecular, covalent compounds, limited to: a low melting points and boiling points, in terms of weak forces between molecules b poor conduction of electricity 3.6 Demonstrate an understanding of the differences between the properties of simple molecular, covalent substances and those of giant molecular, covalent substances, including diamond and graphite 3.8 Describe the separation of two immiscible liquids using a separating funnel 3.9 Describe the separation of mixtures of miscible liquids by fractional distillation, by referring to the fractional distillation of liquid air to produce nitrogen and oxygen 3.10 Describe how paper chromatography can be used to separate and identify components of mixtures, including colouring agents in foodstuffs 3.11 Evaluate the information provided by paper chromatograms, including the calculation of Rf values, in a variety of contexts, such as the food industry and forensic science 17

18 P2.3 Exam Questions- 32 marks, 32 minutes. Questions Q1. Forces and motion (a) The diagram shows some of the forces acting on an airliner in flight. The airliner is flying at a constant height above the ground. Only two of the forces acting on the airliner are shown. (i) Use words from the box to label the diagram. thrust drag lift weight (ii) Draw another arrow on the diagram to show the friction forces acting on the airliner. (iii) The airliner is accelerating. Which of these statements is correct for the accelerating airliner? Put a cross ( ) in the box next to your answer. A the friction forces are zero B the thrust is greater than the friction forces C the thrust is smaller than the friction forces D the thrust is the same size as the friction forces (b) This is a photograph of one of the airliner s jet engines. (i) When the fuel burns, hot exhaust gases are forced backwards out of the engine. Explain why this creates a forward thrust. 18

19 (ii) When the airliner is taking off it accelerates along the runway. It starts from rest and takes off 50 seconds later. Its speed at take off is 60 m/s. Calculate its average acceleration along the runway. acceleration =... m/s 2 (iii) If the same airliner carries fewer passengers but uses the same engine thrust, it can take off in a shorter time. Explain why. Q2. (a) Here is the velocity-time graph for a car for the first 20 s of a journey. (i) Calculate the change in velocity of the car during the first 5 s. (ii) Calculate the acceleration of the car during the first 5 s. acceleration = m/s 2 (iii) State the size of the resultant force between 10 s and 15 s 19

20 (b) The mass of a car is 1200 kg. Calculate the resultant force on the car required to produce an acceleration of 0.8 m/s 2. *(c) A car, travelling at 20 m/s, with just the driver inside takes 70 m to stop in an emergency. The same car is then fully loaded with luggage and passengers as well as the driver. Explain why it will take a different distance to stop in an emergency from the same speed. (6) (Total for Question = 12 marks) 20

21 Q3. (a) A crane is lifting a heavy block from the ground to the top of a building. This is the velocity/time graph for the block as it travels upwards. (i) For how many seconds is the block moving at a constant velocity? This diagram shows one of the forces acting on the block. (ii) Draw an arrow on the diagram to represent the weight of the block. 21

22 (iii) Complete the sentence by putting a cross ( ) in the box next to your answer. When the block is moving upwards at a constant velocity, the resultant force on the block is A upwards and equal to its weight B downwards and equal to its weight C upwards and more than its weight D zero (iv) Use the velocity/time graph to calculate the acceleration of the block during the first 2 s. State the unit. (3) (v) Explain why the upward force from the cable during the first 2 s is greater than the upward force for the next 4 s. (b) A second crane lifts an identical block to the same height. This is the velocity/time graph for the second crane. The graph for the first crane is shown as a dotted line. The second crane has a larger power than the first crane. Explain how the graph shows that the second crane has the larger power. (Total for Question is 10 marks) 22

23 Topic 4: Groups in the periodic table Current Revised RAG Revised 1 Revised 2 3 C2.4 Specification statements C2 Specification 4.1 Classify elements as alkali metals (group 1), halogens (group 7), noble gases (group 0) and transition metals based on their position in the periodic table 4.2 Describe the structure of metals as a regular arrangement of positive ions surrounded by a sea of delocalised electrons 4.3 Describe and explain the properties of metals, limited to malleability and the ability to conduct electricity 4.4 Recall that most metals are transition metals and that their typical properties include: a high melting point b the formation of coloured compounds 4.5 Demonstrate an understanding that elements and compounds can be classified as a ionic, b simple molecular covalent, c giant molecular covalent, d metallic and that each type of substance has different physical properties, including relative melting point and boiling point, relative solubility in water and ability to conduct electricity (as solids and in solution) 4.6 Describe alkali metals as a soft metals b metals with comparatively low melting points 4.7 Describe the reactions of lithium, sodium and potassium with water to form hydroxides which are alkaline, and hydrogen gas 4.8 Describe the pattern in reactivity of the alkali metals lithium, sodium and potassium with water and use this pattern to predict the reactivity of other alkali metals and explain the pattern 4.9 Recall the colours and physical states of the halogens at room temperature 4.10 Describe the reaction of halogens with metals to form metal halides 4.11 Recall that halogens react with hydrogen to produce hydrogen halides which dissolve in water to form acidic solutions 4.12 Investigate displacement reactions of halogens reacting with halide ions in solution 4.13 Describe the relative reactivity of the halogens as shown by their displacement reactions with halide ions in aqueous solution 4.14 Describe the noble gases as chemically inert, compared with the other elements and demonstrate an understanding that this lack of reactivity can be explained by the electronic arrangements in their atoms 4.15 Demonstrate an understanding that the discovery of the noble gases was due to chemists: a noticing that the density of nitrogen made in a reaction differed from that of nitrogen obtained from air b developing a hypothesis about the composition of the air c performing experiments to test this hypothesis and show the presence of the noble gases 4.16 Relate the uses of the noble gases to their properties, including: a inertness (including providing an inert atmosphere for welding and in filament lamps) b low density (including filling balloons) c non-flammability 4.17 Use the pattern in a physical property of the noble gases, such as boiling point or density, to estimate an unknown value foranother member of the group 23

24 P2.4 Exam Questions- 32 marks, 32 minutes. Questions Q1. A pilot begins to land an aircraft. (a) The height of the aircraft decreases from 200 m above the ground to 100 m. (i) What happens to the gravitational potential energy of the aircraft? Put a cross ( ) in the box next to your answer. A it becomes zero B it decreases C it does not change D it increases (ii) The velocity of the aircraft remains constant. What happens to the kinetic energy of the aircraft? Put a cross ( ) in the box next to your answer. A it becomes zero B it decreases C it does not change D it increases (b) The aircraft lands with its wheels on the runway as shown. The aircraft is moving forwards. (i) Draw an arrow on the diagram to show the direction of the momentum of the aircraft. (ii) The velocity of the aircraft when it lands is 75 m/s. The mass of the aircraft is kg. Calculate the momentum of the aircraft. (iii) The aircraft comes to a stop. State the momentum change of the aircraft from when it lands to when it stops. (c) When the aircraft lands, the momentum of each passenger also changes. (i) Explain why it is more comfortable for a passenger if the aircraft takes a longer time to slow down. 24

25 (ii) Suggest why some aircraft need a very long runway to land safely. Q2. The photograph shows a man dropping an egg inside a padded box from a height. (Total for Question is 10 marks) He is investigating to see if the padding stops the egg from breaking. (a) State the type of energy which the egg gains as it falls. (b) The weight of the egg is 0.6 N. Calculate the work done on the egg to lift it up by 20 m. State the unit. (3) (c) The velocity of the container was 18 m/s as it hit the floor. The mass of the container was 0.5 kg. Calculate the momentum of the container. 25

26 *(d) A student stands on the ground with an egg in his hand. He throws the egg vertically upwards. The egg rises to a height of 10 m. Then the egg falls and lands on the ground. Describe the energy changes of the egg during this sequence of events. (6) (Total for Question = 12 marks) Q3. Stopping a car (a) The chart shows how the speed of a car affects the thinking distance and the braking distance. (i) When the speed is 40 km/h, what is the thinking distance? thinking distance =... m (ii) Calculate the thinking distance when the speed is 80 km/h. thinking distance =... m (iii) The total stopping distance of the car is the thinking distance plus the braking distance. Calculate the total stopping distance at 60 km/h. total stopping distance =... m 26

27 (b) As a car becomes old, its braking system wears. This makes the brakes less effective. Describe the effect, if any, that worn brakes have on both the thinking distance and the braking distance. (c) A car takes 9 m to stop after the driver applies the brakes. The brakes exert a force of 2000 N. Calculate how much work is done by this force. work done =... J 27

28 Topic 5: Chemical Reactions Current Revised RAG Revised 1 Revised 2 3 P2.5 Specification statements C2 Specification 5.1 Measure temperature changes accompanying some of the following types of change: a salts dissolving in water b neutralisation reactions c displacement reactions d precipitation reactions 5.2 Define an exothermic change or reaction as one in which heat energy is given out, including combustion reactions or explosions 5.3 Define an endothermic change or reaction as one in which heat energy is taken in, including photosynthesis or dissolving ammonium nitrate in water 5.4 Describe the breaking of bonds as endothermic and the making of bonds as exothermic 5.5 Demonstrate an understanding that the overall heat energy change for a reaction is a exothermic if more heat energy is released making bonds in the products than is required to break bonds in the reactants b endothermic if less heat energy is released making bonds in the products than is required to break bonds in the reactants 5.7 Investigate the effect of temperature, concentration and surface area of a solid on the rate of a reaction such as hydrochloric acid and marble chips 5.8 Recall that the rates of chemical reactions vary from very fast, explosive reactions to very slow reactions 5.9 Describe the effect of changes in temperature and concentration on the rate of reaction 5.10 Describe how reactions can occur when particles collide 5.12 Recall the effect of a catalyst on the rate of reaction 5.13 Demonstrate an understanding that catalytic converters in cars: a have a high surface area, to increase the rate of reaction of carbon monoxide and unburnt fuel from exhaust gases with oxygen from the air to produce carbon dioxide and water b work best at high temperatures 28

29 P2.5 Exam Questions- 45 marks, 45 minutes. Questions Q1. Nuclear fission (a) A student produced this poster to give information about a typical nuclear fission. One word is incorrect in each of the numbered boxes. (i) Circle the incorrect word in each box. Box 1 has been done for you. (ii) Write the correct word in the space under each box. Box 1 has been done for you. 29

30 (b) The diagram shows an outline of a nuclear reactor. When the control rods are lowered the reactor does not produce much thermal energy. Explain what happens when the control rods are raised. *(c) Used nuclear fuel is removed from a reactor for reprocessing. The workers who remove the fuel are at risk. Explain how the safety precautions the workers take help to reduce the risks. (3) (6) 30

31 Q2. Radioactivity is used to sterilise medical equipment such as syringes. The syringes are sealed in strong packets. They are then sent past a source of gamma rays. Explain why gamma rays are used for sterilising medical equipment. Q3. Beryllium-9 is a stable isotope of beryllium. (a) (i) State the meaning of the term stable. (ii) Beryllium-9 has an atomic number of 4 and a mass number of 9. A nucleus of this isotope can be described using this symbol. Complete the sentence by putting a cross ( The number of neutrons in this nucleus is ) in the box next to your answer. A 4 B 5 C 9 D 13 (iii) Which one of these symbols describes the nucleus of a different isotope of beryllium? Put a cross ( ) in the box next to your answer. (b) A beryllium-9 nucleus absorbs a neutron. After a short time the new nucleus splits into two neutrons and two alpha particles. (i) Complete the flow chart for this reaction. 31

32 (ii) Compare this nuclear reaction with the fission of a uranium nucleus. (iii) A fission reaction can be the start of a chain reaction. Describe what needs to happen next to produce a chain reaction. (3) (Total for Question = 10 marks) Q4. (a) The diagram represents an atom of beryllium (Be). (i) State the name of the particle labelled X. (ii) Which of these is the correct symbol for this nucleus of beryllium? Put a cross ( ) in the box next to your answer. (iii) Explain how a beryllium atom can become a positive ion. (b) Nuclear fusion is one type of nuclear reaction. Nuclear fusion reactions release energy in the Sun. Describe what happens during nuclear fusion. 32

33 *(c) Nuclear fission is another type of nuclear reaction. In some nuclear reactors, the controlled fission of uranium-235 (U-235) is used to release thermal energy. Describe the process of fission and its control in a nuclear reactor. You may draw a labelled diagram to help with your answer. (6) (Total for Question is 12 marks) Q5. (a) A student watches a radioactivity demonstration. The demonstration uses this arrangement. The teacher puts different materials in the holder. Then she measures the radiation entering the detector. Here are the results. material in the holder nothing (only air) 121 paper 17 aluminium 17 thick lead 17 radiation entering detector (counts per minute) 33

34 (i) Complete the sentence by putting a cross ( The radiation from the source is A alpha particles B beta particles C gamma rays D X-rays (ii) The teacher returns the radioactive source to the box. Suggest why the box is lined with lead. ) in the box next to your answer. (iii) The counter still gives a reading. The teacher says this is caused by background radiation. State one source of background radiation. (iv) The teacher takes precautions to protect her students from the radiation emitted by the radioactive sources. State two suitable precautions that protect the students. (b) Radon is a radioactive gas which emits alpha particles. (i) A sample of air contains 6 mg of radon. Radon has a half-life of 4 days. Calculate the mass of the radon remaining after 8 days. (ii) Some places have rocks which release radon gas. Explain why people living in these places may have an increased risk of long-term health problems. (Total for Question is 9 marks) 34

35 Topic 6: Quantitative Chemistry Current Revised RAG Revised 1 Revised 2 3 C2.6 Specification statements C2 Specification 6.1 Calculate relative formula mass given relative atomic masses 6.2 Calculate the formulae of simple compounds from reacting masses and understand that these are empirical formulae 6.3 Determine the empirical formula of a simple compound, such as magnesium oxide 6.4 Calculate the percentage composition by mass of a compound from its formula and the relative atomic masses of its constituent elements 6.6 Recall that the yield of a reaction is the mass of product obtained in the reaction 6.7 Demonstrate an understanding that the actual yield of a reaction is usually less than the yield calculated using the chemical equation (theoretical yield) 6.8 Calculate the percentage yield of a reaction from the actual yield and the theoretical yield 6.9 Demonstrate an understanding of the reasons why reactions do not give the theoretical yield due to factors, including: a incomplete reactions b practical losses during the preparation c competing, unwanted reactions 6.10 Demonstrate an understanding that many reactions produce waste products which: a are not commercially useful b can present economic, environmental and social problems for disposal 35

36 P2.6 Exam Questions- 28 marks, 28 minutes. Questions Q1. Everyone is exposed to background radiation. Some of this radiation comes from natural sources. (a) (i) One example of a source of background radiation that does not occur naturally is radiotherapy. State one other source of background radiation that does not occur naturally. (ii) Radon gas is a natural source of background radiation. In some parts of the country, a lot of the background radiation comes from radon gas. Explain why there is no radon gas in some other parts of the country. (b) Technetium-99 is one of the radioactive isotopes in nuclear waste. The graph shows the decay curve for technetium-99. (i) Use the graph to show that the half-life of technetium-99 is about years. (ii) Technetium-99 emits beta particles. Give one reason that beta particles can cause harm to people. 36

37 *(c) There are many radioactive isotopes in nuclear waste. Technetium-99 is just one of these isotopes. People are worried about how we should deal with nuclear waste. Explain why it is difficult to deal with nuclear waste safely. (6) (Total for Question is 12 marks) Q2. (a) Here are four uses of radioactivity. Draw a line from each one of them to the type of radiation it uses. Each type of radiation may be chosen once, more than once or not at all. (4) 37

38 (b) Which graph best shows how the activity of a radioactive isotope changes with time? Put a cross ( ) in the box next to your answer. (c) Complete the sentence by putting a cross ( The unit of activity of a radioactive isotope is the A americium B becquerel C einstein D radium ) in the box next to your answer. 38

39 (d) Describe two precautions that scientists now take when they use radioactive materials. Q3. Using radiation (a) Complete the sentences by putting a cross ( ) in the box next to your answer. (i) Radioactive sources can emit alpha or beta or gamma radiation. An alpha particle is A a helium nucleus B a neutron C a proton D an electron (Total for Question = 8 marks) (ii) A gamma ray is A an electromagnetic wave B a stream of charged particles C emitted from stable nuclei D non-ionising radiation 39

40 (iii) The activity of a radioactive source changes with time. Which of these graphs is correct for a radioactive source? Put a cross ( ) in the box next to your answer. (b) In the past, people thought that radiation could cure many illnesses. Some people drank water from containers lined with the radioactive element radium. Complete the sentence by putting a cross ( ) in the box next to your answer. Today we have laws and rules about how radioactive sources are used and handled. This is because A doctors are better trained now B radioactive sources have become more dangerous C the dangers of radioactive sources are better understood now D we can work out the half-life of radioactive sources 40

41 (c) Radioactivity is used to sterilise medical equipment such as syringes. The syringes are sealed in strong packets. They are then sent past a source of gamma rays. Explain why gamma rays are used for sterilising medical equipment. (d) Describe one other use of a radioactive source. 41