Plot Twist

Plot Twist: plot real results, draw the line of best fit and watch a stunt robot ride it

This free game is part of our AQA GCSE Chemistry (8462) course for exams in EXAM YEARS 2027-2029.

Presenting and processing data for AQA GCSE Chemistry

Every AQA GCSE Chemistry (8462) paper has marks for working with data: plotting a graph, drawing a line of best fit, spotting an anomaly, calculating a mean and a range, giving an answer to the right number of significant figures and finding a slope or a tangent. These are the Working Scientifically skills WS 3.1 to 3.4. Reading the rules is easy. Doing them well on a real set of results is where marks are lost.

In Plot Twist you work in Fizz Lab with Lena, the Head of Data. Each experiment runs on the lab bench and its readings go into a results table. You turn them into a graph on a giant graph wall, and then ACE, the lab's stunt robot, rides whatever line you drew.

Plot the points and draw a line of best fit, not dot to dot

You plot each reading by tapping the graph, with a magnifier to help you aim. A cross within half a small square of the right place scores; anything further out turns red and a card shows exactly how to read that scale, because one small square is rarely worth 1. You also choose which variable goes on the x-axis (the independent variable), the right axis label with its unit, and a scale that uses more than half the grid.

Then you draw the line of best fit. Draw one smooth curve through the trend and ACE glides along it, collecting every point. Join the dots and he hits a jolt at every corner and wipes out. Bend your line towards the anomaly (the bung popped out, so gas escaped) and he gets thrown off. Use the ruler when the points lie in a straight line, and the pen when they curve. A fit score compares your line with the best one.

Bar charts, histograms and frequency tables

The kind of data decides the kind of chart. Temperature rises for magnesium, zinc, iron and copper in dilute acid are categories, so you build a bar chart by pulling each bar to its value, and ACE has to jump the gaps between the bars. Twenty soil pH readings are groups of numbers, so you sort them Tetris-style into pH groups. The blocks stack up into a histogram with bars that touch, and the tally and frequency table fill in as you go. The frequencies add up to 20: a quick check that nothing was missed.

Mean, range, uncertainty and significant figures

Five repeat masses of a precipitate sit on a balance beam at their values. Drag the pivot until the beam is level and you have found the mean: it is the balance point. One reading, 1.62 g, is an anomaly that drags the mean up to 1.456 g. Knock it off, rebalance, and the mean of the four good readings is 1.415 g. A calculator display then asks you to cut 1.415 to 3 significant figures, the same as the readings, giving 1.42 g. The range is 1.38 g to 1.45 g, and half of it about the mean shows the uncertainty: 1.42 g ± 0.04 g. Two lightning rounds practise rounding numbers like 0.004052 and 3078.

Slope, intercept, tangents and the area under a curve

On a straight-line graph you drag a big gradient triangle along the line: slope = change in y ÷ change in x, about 1000 cm³ of hydrogen per gram of magnesium, and the intercept is 0. For Higher tier, you turn a launch ramp until it is the tangent to a curve, then ACE launches off it. The slope of the tangent is the rate of reaction at that moment, not the volume divided by the time. You also rearrange mean rate = quantity ÷ time, and watch ACE paint the area under a rate–time curve: rate × time gives the total volume of gas, counted in squares.

The game takes about 8 minutes, starts with a guided first move, works with a mouse, touch screen or keyboard, is readable on a projector and saves your best score.