1. (a) The diagrams below show the arrangement of atoms or molecules in five different substances A, B, C, D and E.

Transcription

1 Level 7 Chemistry Questions 1. (a) The diagrams below show the arrangement of atoms or molecules in five different substances A, B, C, D and E. Each of the circles, and represents an atom of a different element. Give the letter of the diagram which represents: (i) a mixture of gases;... (ii) a single compound.... (b) The diagram below shows a model of a chemical reaction between two substances. (i) How can you tell from the diagram that a chemical reaction took place between substance P and substance Q? Moulsham High School 1

2 (ii) Substance P is carbon. Suggest what substances Q and R could be. substance Q... substance R... (iii) How does the diagram show that mass has been conserved in this reaction? maximum 5 marks 2. In the eighteenth century, scientists had different ideas about what happens when metals burn in air. (a) Imagine you want to investigate the ideas of Priestley and Lavoisier. Assume you have been given three pieces of different metals. In a laboratory, metals are heated to high temperatures in crucibles. Moulsham High School 2

3 You would also have access to all the usual laboratory equipment. In your plan you must give: the one factor you would change as you carry out your investigation (the independent variable); one factor you would observe or measure to collect your results (the dependent variable); one of the factors you would keep the same as you carry out your investigation; the evidence that would support Lavoisier s idea marks Moulsham High School 3

4 (b) In the box below, draw and label a table you could use to record your results. maximum 5 marks Moulsham High School 4

5 3. Part of the reactivity series of metals is shown below. most reactive potassium sodium magnesium aluminium iron lead least reactive copper (a) Dan added a piece of magnesium to a solution of copper sulphate. A displacement reaction took place. The word equation for the reaction is shown below. magnesium + copper sulphate magnesium sulphate + copper Why is this called a displacement reaction? (b) Look at each pair of chemicals in the table below. Use the reactivity series to predict whether a displacement reaction would take place. Write yes or no in the second column and give the reason for your decision. pairs of chemicals Does a displacement reaction take place? yes or no reason iron + sodium chloride magnesium + lead nitrate 2 marks Moulsham High School 5

6 (c) Dan wanted to find out where zinc should be placed in the reactivity series. (i) What tests should Dan do to find the correct position of zinc in the reactivity series? (ii) How would Dan use his test results to decide where to put zinc in the reactivity series? maximum 5 marks 4. As apples become ripe they produce a gas called ethene. Ethene passes through the air from ripe apples to unripe apples. Ethene causes unripe apples to ripen more quickly. (a) Three effects of ethene on apples are listed below. The green substance, chlorophyll, breaks down. Starch breaks down to form glucose. Pectin, a substance which holds cells together, breaks down. Describe and explain the changes you would notice when apples become ripe as a result of any two of these effects. 1. change explanation change explanation Moulsham High School 6

7 (b) Give the name of the process by which gases such as ethene spread through the air in a room.... (c) The diagram below represents a molecule of ethene. Ethene is flammable and must be kept away from naked flames. Look at the diagram of the molecule of ethene. Give the name and chemical formula of the two compounds formed when ethene burns in oxygen. 1. name... formula name... formula... maximum 5 marks Moulsham High School 7

8 5. In the 19th Century, a scientist called John Dalton used symbols to represent atoms. The symbols he used for atoms of three different elements are shown below. The diagrams below show different combinations of these atoms. A B C D E (a) (i) Give the letter of the diagram which shows a mixture of two elements.... (ii) Give the letter of the diagram which shows a mixture of two compounds.... (iii) Give the letter of the diagram which shows a mixture of an element and a compound.... (b) Give one difference between a compound and a mixture Moulsham High School 8

9 (c) (i) Suggest a name and formula for the substance represented in diagram B. name... formula... (ii) Suggest a name and formula for the substance represented in diagram D. name... formula... maximum 6 marks 6. The chemical name for pure limestone is calcium carbonate. When calcium carbonate is heated to a temperature above 825 C it produces calcium oxide and carbon dioxide. (a) Complete the symbol equation for this reaction. CaCO marks (b) The photograph shows a limestone statue that has been changed by acid rain. Some gases which pollute the air dissolve in rainwater to form acids. Moulsham High School 9

10 (i) Give the name of a gas which dissolves in rainwater, leading to the formation of sulphuric acid. (ii) Complete the word equation for the reaction between calcium carbonate and sulphuric acid. calcium + sulphuric water carbonate acid 2 marks maximum 5 marks 7. A pupil used a sensor to record the change in ph of 10 cm 3 of an acid solution when an alkali solution was added a little at a time. The concentrations of the alkali and acid solutions were fixed. His results are shown in the table below. volume of alkali added (cm 3 ) ph of resulting mixture (a) Use his results to draw a graph on the grid below. Moulsham High School 10

11 Label the axes. Plot the points. Draw a smooth curve. 4 marks (b) Look at the graph. What would be the likely ph of the solution if the pupil added a further 2 cm 3 of alkali solution?... maximum 5 marks Moulsham High School 11

12 8. The diagram shows an exhibit at a science museum. It has six blocks of metal connected to a voltmeter. (a) On the lines on the diagram, write the chemical symbols for magnesium and copper volts magnesium tin Sn copper zinc Zn aluminium Al nickel Ni 2 marks (b) When visitors place their hands on two blocks of metal at the same time, there is a reading on the voltmeter. Some examples are shown in the table. hands placed on reading on voltmeter (volts) magnesium + tin 2.1 magnesium + copper 2.5 magnesium + zinc 1.5 magnesium + aluminium 0.6 magnesium + nickel 2.0 The reading on the voltmeter depends on the reactivity of the two metals touched. The bigger the difference in reactivity, the higher the reading on the voltmeter. Moulsham High School 12

13 (i) Magnesium is the most reactive of these metals. Which metal is the least reactive?... (ii) If two blocks of magnesium are used in the experiment, instead of two different metals, what would the voltmeter read?... volts Explain your answer. 2 marks (iii) Look at the voltmeter readings in the table. On which two metals, other than magnesium, would a person put their hands to give the lowest reading on the voltmeter?... and... maximum 6 marks 9. (a) Magnesium chloride is formed when magnesium reacts with an acid. (i) Complete the word equation for the reaction between magnesium and this acid. magnesium +... magnesium +... chloride 2 marks (ii) Suggest why magnesium chloride can be made by mixing magnesium with this acid but copper chloride cannot be made by mixing copper with this acid. (b) Copper sulphate is made by adding copper oxide to a different acid. Give the name of the acid which is used.... Moulsham High School 13

14 (c) In the table below, write the name of the compound represented by each formula. formula name CuSO 4 MgCl 2 2 marks Maximum 6 marks 10. (a) Complete the word equation below for the reaction between calcium carbonate and hydrochloric acid. calcium hydrochloric carbon carbonate acid dioxide + water Limestone is mainly calcium carbonate. It is weathered by acids in the air or in soil. (b) In June 1990, a Year 9 class planned a long-term investigation into the chemical weathering of limestone by acids in soil. They put limestone chippings of similar size in three nylon mesh bags. They buried the bags outside in soils of different ph. (i) Chemical weathering took place in sample A, and the mass of the sample decreased. Give the reason for the decrease in mass. Use the word equation above to help you. Moulsham High School 14

15 (ii) The pupils predicted that chemical weathering would not take place in samples B and C. Give the reason for their prediction. (iii) Some chemical weathering did take place in samples B and C. What could have changed the conditions in these soils to cause weathering to take place? (c) The table shows how the mass of each sample changed between the years 1990 and year sample A, at ph 5 mass, in g sample B, at ph 7 sample C, at ph In 2000, a year 9 class buried another identical 1000 g sample of limestone chippings in soil of ph 6. (i) Use the results in the table to predict an approximate value for the mass of this sample in g (ii) Why is it not possible to be certain what the mass of this sample will be in 2010? Maximum 6 marks Moulsham High School 15

16 11. A group of pupils placed pieces of metal wire in different salt solutions. They recorded their observations in the table below. (a) From these observations, write the order of reactivity of the four metals, copper, lead, silver and zinc. most reactive least reactive... 2 marks (b) The pupils then dipped a new piece of each of the metal wires into dilute hydrochloric acid. Only one of the metals reacted. Which metal was this?... Moulsham High School 16

17 (c) One pupil predicted that there would be no reaction when he put a piece of zinc wire into a solution of silver nitrate. Was his prediction correct? Explain your answer (d) In nature, gold is never found combined with other elements. Where should gold be placed in the reactivity series in part (a)? Explain your answer Maximum 5 marks 12. A headline from a newspaper is shown below. British Power Stations cause Acid Rain in Scandanavia Some countries claim that acid rain caused by power stations in Britain damages their forests. Others argue that coal-burning power stations produce cheap electricity and that plants can stand some level of acid rain. Imagine you are planning a laboratory investigation of the claim: plants can stand some level of acid rain. Assume you have access to whatever laboratory equipment you need, including: seeds acid seed trays soil Plan a laboratory investigation to test the claim that plants can stand some level of acid rain. Moulsham High School 17

18 (a) Name a factor you would need to vary in your investigation. (This is the independent variable.)... (b) (i) What factor would you examine to see the effect? (This is the dependent variable.) (ii) How could you measure this dependent variable? (c) Suggest one factor you would control to ensure that your investigation is fair.... Maximum 4 marks Moulsham High School 18