A student investigated the effect of changing ph and temperature on the digestion of lactose in milk

Transcription

1 Q1. Fresh milk is a mixture of compounds including fat, protein and about 5 % lactose sugar. Lactose must be digested by the enzyme lactase, before the products can be absorbed. Lactase can be added to fresh milk to pre-digest the lactose. This makes lactose-free milk, which is suitable for people who do not produce enough lactase of their own. A student investigated the effect of changing ph and temperature on the digestion of lactose in milk. The results are shown in Tables 1 and 2. Table 1 Effect of ph Table 2 Effect of temperature ph Time taken to digest lactose in minutes Temperature in C Time taken to digest lactose in minutes (a) The label on a carton of lactose-free milk states: Lactase is normally produced in the stomach of mammals. The results in Table 1 show that this statement is unlikely to be true. Explain how Page 1 of 32

2 (b) Explain as fully as you can the results shown in Table (3) (c) Bile is produced in the liver and is released into the small intestine. Explain how bile helps the digestion of milk (Total 7 marks) Page 2 of 32

3 Q2. The diagram shows the apparatus used to investigate the digestion of milk fat by an enzyme. The reaction mixture contained milk and the enzyme. In Experiment 1, bile was also added. In Experiment 2, an equal volume of water replaced the bile. In each experiment, the ph was recorded at 2 minute intervals. The results of the two experiments are given in the table. Time in minutes Experiment 1: with bile ph Experiment 2: without bile (a) Milk fat is a type of lipid. Explain why the ph changed in experiment Page 3 of 32

4 (b) For Experiment 1, calculate the average rate of fall in ph per minute, between 4 minutes and 8 minutes. Show clearly how you work out your final answer.... ph units per minute The average rate of fall in ph per minute for Experiment 2 was 0.1 units of ph per minute. Explain the difference in the rate of fall in ph when bile is present. (Total 5 marks) Q3. The table shows the number of chromosomes found in each body cell of some different organisms. Animals Plants Species Number of chromosomes in each body cell Species Number of chromosomes in each body cell Fruit fly 8 Tomato 24 Goat 60 Potato 44 Human 46 Rice 24 (a) Nearly every organism on earth has an even number of chromosomes in its body cells. Suggest why Page 4 of 32

5 (b) Chromosomes contain DNA molecules. Describe the function of DNA (c) Gametes are made in the testes by meiosis. Look at the diagrams. Which diagram, A, B, C or D, represents how cell division by meiosis produces gametes in the testes? How many chromosomes will each goat gamete contain? Page 5 of 32

6 (d) Body cells divide by mitosis. Why is the ability of body cells to divide important? When a body cell of a potato plant divides, how many chromosomes will each of the new cells contain? (Total 7 marks) Q4. A gardener grows tomatoes. He wants to find out how to get the biggest mass of tomatoes. He plants different varieties of tomato against different walls in his garden. Use these results to answer the questions. (a) The gardener wants his test to be fair. Name one condition which he should keep the same for all his tomato plants Page 6 of 32

7 (b) The table shows the gardener s results. Variety of tomato plant Wall they were planted against Mean mass of tomatoes produced in kilograms per plant Sungold Sungold Sungold Sungold Nugget Champion North West South East East East To obtain the biggest mass of tomatoes, against which wall is it best to grow the tomato plants? Tick ( ) one box. North wall South wall East wall West wall To obtain the biggest mass of tomatoes, which variety of tomato plant would it be best to grow?... (c) From the information in the table, the gardener s test was not fair. Give one way in which the test was not fair (Total 4 marks) Page 7 of 32

8 Q5. Diagram 1 shows a cell from a leaf. Diagram 1 (a) How is the leaf cell specialised to carry out photosynthesis? Tick ( ) one box. It has a permanent vacuole. It has many chloroplasts. It has cytoplasm. It has many mitochondria. Page 8 of 32

9 (b) Diagram 2 shows another type of plant cell. Diagram 2 Give two ways in which this cell is different from an animal cell (Total 3 marks) Q6. Cystic fibrosis is an inherited disorder that can seriously affect health. (a) Which one of these is affected by cystic fibrosis? Draw a ring around your answer. blood cell membranes kidneys nervous system Page 9 of 32

10 (b) The diagram shows the inheritance of cystic fibrosis in a family. The allele that produces cystic fibrosis is recessive. Explain why Alice inherited cystic fibrosis Explain why Ted did not inherit cystic fibrosis Page 10 of 32

11 (c) Bob and Carol know that there is a risk that their next baby will have cystic fibrosis. Embryos can be screened for the allele that produces cystic fibrosis. Many people support the screening of embryos, but others do not. Suggest one reason why many people support the screening of embryos for the cystic fibrosis allele Suggest one reason why many people are against the screening of embryos for the cystic fibrosis allele (Total 7 marks) Q7. Humphrey Davy was a professor of chemistry. In 1807 Humphrey Davy did an electrolysis experiment to produce potassium. (a) Humphrey Davy was the first person to produce potassium. Draw a ring around the correct answer to complete each sentence. Humphrey Davy s experiment to produce this new element was quickly accepted by had a lot of money. other scientists because he had a lot of staff to help. was well qualified. Page 11 of 32

12 Other scientists were able to repeat Davy s experiment. Draw a ring around the correct answer to complete each sentence. Being able to repeat Davy s experiment is important because check the results of the experiment. other scientists can see if the experiment is safe. take the credit for the discovery. (b) A student tried to electrolyse potassium chloride. Potassium chloride contains potassium ions (K + ) and chloride ions (Cl ). The student found that solid potassium chloride does not conduct electricity. Use the correct answer from the box to complete the sentence. are too big cannot move have no charge Solid potassium chloride does not conduct electricity because the ions.... What could the student do to the potassium chloride to make it conduct electricity? (iii) During electrolysis why do potassium ions move to the negative electrode? Page 12 of 32

13 (iv) Draw a ring around the correct answer to complete the sentence. When the potassium ions reach the negative electrode atoms. they turn into potassium electrodes. molecules. (Total 6 marks) Q8. This question is about salts of ammonia and salts of lead. (a) Ammonia dissolves in water to make an alkaline solution. Draw a ring around the correct answer to complete each sentence. The ph of a solution of ammonia is (b) Ammonia can be reacted with an acid to produce the salt ammonium nitrate. Name the acid used to produce ammonium nitrate.... Draw a ring around the correct answer to complete each sentence. neutralisation The reaction of ammonia with an acid is a polymerisation reaction. reduction (c) Why do farmers use ammonium nitrate on their fields? (d) Lead iodide is a salt that can be produced without using an acid. Lead iodide is produced by mixing two solutions. Complete the word equation. lead... + potassium... lead iodide + potassium nitrate Page 13 of 32

14 The lead iodide is produced as a solid. Complete the sentence. A solid that is produced when two solutions are mixed is called a.... (iii) How could the solid lead iodide be separated from the solution? (iv) A student mixed two solutions to make sodium chloride. The equation for the reaction the student used is: HCl(aq) + NaOH(aq) NaCl(aq) + H 2 O(l) How could the student obtain solid sodium chloride from the solution? (Total 9 marks) Page 14 of 32

15 Q9. Scientists have recently developed a method to produce large sheets of a substance called graphene. Graphene is made from carbon and is a single layer of graphite just one atom thick. The properties of graphene include: it conducts electricity it is transparent since it is only one atom thick it is strong and durable. These properties make it suitable to overlay a monitor screen to make it a touchscreen. The photograph below shows the structure of graphene. Photographs supplied by istockphoto/thinkstock Use your knowledge of the bonding in graphite and the photograph of the structure to help you to explain, as fully as you can: (a) why graphene is strong; (3) Page 15 of 32

16 why graphene conducts electricity. (b) Suggest why a sheet of graphite which has a large number of carbon layers would not be suitable for the touchscreen (Total 6 marks) Q10. Hand warmers use chemical reactions. (a) The table shows temperature changes for chemical reactions A, B and C. Reaction Starting temperature in C Final temperature in C Change in temperature in C A B C What is the final temperature for reaction B? Write your answer in the table. (b) What name is given to reactions that heat the surroundings?... Page 16 of 32

17 Which reaction, A, B or C, would be best to use in a hand warmer? Reaction Give a reason why you chose this reaction (c) A student added water to some anhydrous copper sulfate. The equation for the reaction is shown. anhydrous copper sulfate + water hydrated copper sulfate CuSO H 2 O CuSO 4.5H 2 O The student measured the temperature before and after the reaction. The measurements showed that this reaction can be used for a hand warmer. Draw a ring around the correct answer to complete the sentence. When water is added to anhydrous copper sulfate the temperature increases. of the mixture decreases. stays the same. Anhydrous copper sulfate is white. What colour is seen after water is added to the anhydrous copper sulfate?... Page 17 of 32

18 (iii) What does the symbol mean?... (iv) The student heated a tube containing hydrated copper sulfate. Name the solid substance produced.... (Total 8 marks) Q11. Aluminium is extracted from aluminium oxide. (a) The formula of aluminium oxide is Al 2 O 3 The relative formula mass (M r ) of aluminium oxide is 102. Calculate the percentage of aluminium in aluminium oxide. Relative atomic masses (A r ): O = 16; Al = Percentage of aluminium =... % Page 18 of 32

19 (b) Aluminium is extracted from aluminium oxide using electrolysis. The diagram shows a cell used for the extraction of aluminium. The electrolyte contains cryolite. Explain why. Oxygen is formed at the positive electrode. Complete and balance the equation for this reaction.... O 2- O (iii) The positive electrode in the cell is used up during the process. Explain why. (Total 8 marks) Page 19 of 32

20 Q12. (a) The diagram shows a builder using a plank to help load rubble into a skip. The builder uses a force of 220 N to push the wheelbarrow up the plank. Use information from the diagram and the equation in the box to calculate the work done to push the wheelbarrow up the plank to the skip. work done = force applied distance moved in the direction of force Show clearly how you work out your answer Work done =... J Page 20 of 32

21 (b) A student investigated how the force needed to pull a brick up a slope, at a steady speed, depends on the angle of the slope. The apparatus used by the student is shown in the diagram. The student used the results from the investigation to plot the points for a graph of force used against the angle of the slope. Draw a line of best fit for these points. How does the force used to pull the brick up the slope change as the angle of the slope increases? Page 21 of 32

22 (iii) Consider the results from this experiment. Should the student recommend that the builder use a long plank or a short plank to help load the skip? Draw a ring around your answer. long plank short plank Explain the reason for your answer. (Total 6 marks) Page 22 of 32

23 Q13. The diagram shows the velocity-time graph for an object over a 10 second period. (a) Use the graph to calculate the distance travelled by the object in 10 seconds. Show clearly how you work out your answer Distance =... m Page 23 of 32

24 (b) Complete the distance-time graph for the object over the same 10 seconds. (Total 4 marks) Page 24 of 32

25 Q14. The diagram represents an atom of lithium. (a) Complete the following table of information for an atom of lithium. Number of protons Number of electrons Number of neutrons What is the mass number of a lithium atom? Draw a ring around your answer Give a reason for your answer. (b) Complete the following sentence by drawing a ring around the correct line in the box. an ion An atom that has lost an electron is called an isotope a positive atom Page 25 of 32

26 (c) When an alpha particle is emitted from the nucleus of a radon atom, the radon changes into polonium. An alpha particle consists of 2 protons and 2 neutrons. Complete the following sentence by drawing a ring around the correct line in the box. greater than The mass of a polonium atom is the same as the mass of a radon atom. smaller than Give a reason for your answer to part (c). (Total 7 marks) Q15. (a) In any collision, the total momentum of the colliding objects is usually conserved. What is meant by the term momentum is conserved? In a collision, momentum is not always conserved. Why? Page 26 of 32

27 (b) The diagram shows a car and a van, just before and just after the car collided with the van. Before collision After collision Use the information in the diagram and the equation in the box to calculate the change in the momentum of the car. momentum = mass velocity Show clearly how you work out your answer and give the unit. Change in momentum =... (3) Use the idea of conservation of momentum to calculate the velocity of the van when it is pushed forward by the collision. Show clearly how you work out your answer. Velocity =... m/s forward (Total 7 marks) Page 27 of 32

28 Q16. (a) The diagram shows a cable car used to take skiers to the top of a mountain. The total mass of the cable car and skiers is 7500 kg. Use the equation in the box to calculate the weight of the cable car and skiers. weight = mass gravitational field strength gravitational field strength = 10 N/kg Show clearly how you work out your answer and give the unit. Weight =... (3) The cable car moves at a constant speed. It lifts skiers through a vertical height of 800 metres in 7 minutes. Use the following equation to calculate the work done to lift the cable car and skiers. work done = force applied distance moved in the direction of force Show clearly how you work out your answer. Work done =... J Page 28 of 32

29 (b) The diagram shows a skier who is accelerating down a steep ski slope. Draw an arrow on the diagram to show the direction of the resultant force acting on the skier. How and why does the kinetic energy of the skier change? (c) Last year, skiers suffered a head injury. It is thought that nearly 8000 of these injuries could have been avoided if the skier had been wearing a helmet. However, at present, there are no laws to make skiers wear helmets. Suggest why skiers should be made aware of the benefits of wearing a helmet (Total 9 marks) Q17. In the UK mains electricity is a 230 volt a.c. supply. (a) What is the frequency of the a.c. mains electricity in the UK?... (b) What is an electric current? Page 29 of 32

30 Explain the difference between an a.c. (alternating current) electricity supply and a d.c. (direct current) electricity supply. (c) A householder has a 10.8 kw electric shower installed in the bathroom. Calculate the current drawn from the mains electricity supply by the shower. Write down the equation you use, and then show clearly how you work out your answer. Current =... A Page 30 of 32

31 The table gives the maximum current that can safely pass through electric cables of different cross-sectional area. Cross-sectional area in mm 2 Maximum safe current in amps The existing power sockets in the house are wired to the mains electricity supply using 2.5 mm 2 cable. Use the data in the table to explain why the shower must not be connected to the mains electricity supply using 2.5 mm 2 cable. (iii) The circuit connecting the shower to the mains electricity supply must include a residual current circuit breaker (RCCB) and not a fuse. Give two advantages of using a RCCB to protect a circuit rather than a fuse (Total 10 marks) Page 31 of 32

32 Page 32 of 32