AQA GCSE · Question 02.5 · Atomic structure and the periodic table
Estimate the density (X) of krypton.
Use your plotted graph and Table 1.
How to approach this question
1. Draw a smooth curve of best fit through the points you plotted on the graph.
2. Find the atomic number of Krypton from Table 1 (it is 36).
3. Locate 36 on the x-axis of your graph.
4. Draw a line up from 36 to your curve of best fit.
5. From that point on the curve, draw a horizontal line across to the y-axis.
6. Read the value from the y-axis. This is your estimate for the density of Krypton.
Full Answer
3.2 mg/cm³ (Accept answers in the range 3.0 - 3.4)
The points on the graph show a clear trend: as the atomic number increases, the density increases. By drawing a smooth curve of best fit through the plotted points, we can interpolate to find the value for krypton. Krypton has an atomic number of 36. Finding 36 on the x-axis and reading up to the curve, then across to the y-axis, gives a density value of approximately 3.2 mg/cm³. Any value within a reasonable range (e.g., 3.0 to 3.4) is acceptable as it depends on the exact curve drawn.
Common mistakes
✗ Just guessing a number without using the graph.
✗ Reading the value from the wrong axis.
✗ Drawing a poor line of best fit that does not follow the trend of the points.
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