Lesson 1 of 7
Read unfamiliar data
Select evidence and connect it to a chemical principle.
SEC G2 Science K223 / K225 (2027)
I can interpret and evaluate data and observations.Syllabus
Syllabus K223 / K225, C3. Interpret and evaluate data and observations
Read unfamiliar data with a purpose
Separate the question, the evidence and the chemistry that connects them.
Start with the quantity or claim the question asks you to establish. Then locate the relevant measurements, conditions and any new definitions in the stem. An unfamiliar substance name does not make its data unusable: use the supplied information together with a familiar idea such as conservation of atoms, collision frequency or intermolecular attraction.
- Name the task
For a calculation, identify the required quantity and unit. For an explanation, identify the observation that needs explaining.
- Select the evidence
Extract the relevant rows, axes and conditions. Distinguish a measurement from a proposed explanation; do not use every number just because it is present.
- Connect a principle
State the chemical relationship that makes the evidence relevant. Check that the comparison holds other important variables constant.
- State the result and its limit
Give a numerical answer with units, or a conclusion supported by a specific comparison. State an assumption where the inference depends on it.
Worked exampleAssess a claim about a catalyst
Two runs use the same amount of reactant and the same temperature. Run A gives 40 cm3 of gas in 20 s; run B gives 40 cm3 in 50 s. Both eventually give 60 cm3. A report says: "A produces more product because it is faster."
Try it first. Then show the worked stepsHide the worked steps
- The time to reach the same volume is smaller for A: its average rate to 40 cm3 is 2.0 cm3 s-1, compared with 0.80 cm3 s-1 for B.
- The final volumes are the same under the same collection conditions, so these data do not show more final gaseous product in A.
- The evidence supports faster production, not a greater final amount. Identifying the cause as a catalyst also requires the stated experimental difference between the runs.
Compare rate using a time interval and final amount using the plateau. They answer different questions.
Check your understanding
A table gives temperature, concentration, reaction time and the colour of the laboratory bench. Which data belong in an explanation of the rate trend?
Show the answer
Temperature, concentration and reaction time, after checking which one was changed
Use the variables that can affect rate, and find out which one was varied. Bench colour has no chemical role, so do not invent a link just because a detail is given.
Exam-style question
Data-based questionA school is next to a bus interchange. Students used a sensor to measure two gases in the air at the school gate on one weekday. They also counted the buses that arrived each hour. The unit ppm means parts per million and ppb means parts per billion. Both are ways of measuring very small amounts of a gas in air.
Table 1. Air at the school gate time buses per hour carbon monoxide / ppm nitrogen dioxide / ppb 06:00 10 0.8 20 08:00 45 3.6 70 10:00 25 2.0 45 14:00 20 1.7 42 18:00 50 4.0 78 22:00 8 0.7 18
- (a) State the time when the carbon monoxide level was highest. Give the reading with its unit. [1]
- (b) Describe how the carbon monoxide level changes with the number of buses. Quote two pairs of readings. [2]
- (c) Explain how a bus engine produces carbon monoxide. [1]
- (d) Explain how nitrogen dioxide forms in a bus engine. [1]
- (e) State why carbon monoxide is harmful to the students. [1]
- (f) The principal says: "These readings prove that all the nitrogen dioxide at the gate comes from the buses." Use the data to explain whether you agree. [2]
[8]
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