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AQA · GCSE · Chemistry · Higher

Drawing intersecting best-fit lines

Q04.1 2 marks

A student investigated the energy change of the reaction between zinc and copper sulfate solution.

  1. Measure 25 cm³ of copper sulfate solution into a polystyrene cup.
  2. Measure the temperature of the copper sulfate solution.
  3. Add 0.20 g of zinc powder to the copper sulfate solution.
  4. Stir the reaction mixture.
  5. Record the highest temperature reached.
  6. Repeat steps 1 to 5 with different masses of zinc powder.

Figure 3 shows the results.

Draw two lines of best fit on Figure 3. The lines should cross.

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Marking points

  1. 1 A suitable best-fit line represents the first five plotted points.
  2. 2 A suitable best-fit line represents the last four plotted points and intersects the first line.

Why this answer loses marks

I drew one smooth curve through all the points.

The graph has separate rising and plateau regions, each needing its own crossing fitted line.