A group of students uses the following method to investigate the change in mass that takes place when metal M combines with sulfur to form a metal sulfide. step 1 Weigh a clean crucible and lid using a balance. Record the mass. step 2 Place a coiled length of metal wire into the crucible and weigh the crucible, lid and wire. step 3 Cover the metal wire in the crucible with a large quantity of powdered sulfur and replace the lid. step 4 Heat the crucible in a fume hood until the crucible glows red. Continue heating strongly until no more sulfur can be seen. step 5 Allow the apparatus to cool and weigh the crucible, lid and residue.

1. (a)(i)Fig. 2.1 shows how the apparatus is set up when heating the crucible in step 4. Identify the missing piece of apparatus used to support the crucible during heating. [1][1]
2. (a)(ii)Suggest why the students heat their crucibles in a fume hood in step 4. [1][1]
3. (a)(iii)Suggest why a large quantity of powdered sulfur is used in step 3. [1][1]
4. (b)Five students each use a different mass of M. Their results are shown in Table 2.1. Complete Table 2.1 by inserting values for the mass of M and the mass of sulfur which reacts for each student. Table 2.1 student 1 student 2 student 3 student 4 student 5 mass of crucible and lid/g 34.15 38.28 35.68 33.70 36.84 mass of crucible, lid and M/g 35.58 39.42 36.54 34.27 37.13 mass of crucible, lid and residue after heating/g 36.04 39.70 36.74 34.42 37.19 mass of M/g mass of sulfur which reacts/g [1][1]
5. (c)Identify the independent variable in this experiment. [1][1]
6. (d)(i)Plot a graph on the grid in Fig. 2.2 to show the relationship between mass of sulfur which reacts and mass of M. Use a cross (x) to plot each data point. Draw a straight line of best fit which includes the origin. [2][2]
7. (d)(ii)Circle the point on the graph you consider to be most anomalous. Suggest one reason why this anomaly may have occurred during this experimental procedure. Assume no error was made in the measurement of any mass. [2][2]
8. (e)Determine the gradient of your line of best fit. State the coordinates of both points you used in your calculation. These must be selected from your line of best fit. Give your gradient to three significant figures. coordinates 1 .............................................. coordinates 2 .............................................. gradient = .............................................. [2][2]
9. (f)Use your line of best fit in Fig. 2.2 to determine if the results obtained by the students are reliable. Explain your answer. [1][1]
10. (g)(i)Deduce the gradient of the line of best fit for the graph of mass of sulfur which reacts against mass of strontium for the compound SrS. gradient .............................................. [1][1]
11. (g)(ii)Use your answer to (i) to explain if the results of the experiment support the student's suggestion. [1][1]

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