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Grade 8 science asks more of you than remembering facts. The first chapter of the new book says it plainly: the aim is not just to learn new facts but to learn how to find them. This guide is for students and parents. It explains what the chapter covers, what the research says about learning to run a fair test, a worked example using the chapter's own puri question, and a routine to use all year.
What is in the first chapter of Class 8 Curiosity?
Exploring the Investigative World of Science is Chapter 1 of Curiosity, the NCERT science textbook for Grade 8 (reprint 2026-27), which has 13 chapters. The chapter 1 PDF is short. It opens with questions meant to spark curiosity, not to test you: why is one side of a puri thinner than the other, and are there more grains of sand on Earth's beaches and deserts or more stars in our galaxy?
It then previews the year: microbes, health, electricity, forces, pressure and cyclones, particles, elements and mixtures, solutions, light, the Moon's phases and calendars, ecosystems, and finally what makes Earth suitable for life. It links back to Grade 6, where science began with wonder, and Grade 7, where science was shown to keep changing.
What does investigating mean in this chapter?
The chapter walks through the puri question step by step:
Ask a scientific question: what changes how a puri puffs up when fried?
List what you can change: dough thickness and size, type of flour (atta or maida), oil temperature, and how you drop the dough in.
List what you can observe or measure: whether it puffs (yes or no), how many seconds it takes, whether a thick puri still has a thin side.
Change only one thing at a time and keep everything else the same.
Write down everything, including splatter, smell and smoke, and note new questions.
The chapter adds that even the puffing of a puri is not completely understood by scientists today.
Can the fair-test habit be taught?
Yes, and directly. Psychologists call it the control of variables strategy. Chen and Klahr (1999) worked with 87 children aged 7 to 10. Children who got explicit teaching on designing unconfounded experiments, along with probe questions, learned the strategy and transferred it to new contexts. Probe questions alone, without the teaching, did not improve their designs.
A later study by Klahr and Nigam (2004) with 112 third and fourth graders found that many more children learned the strategy from direct instruction than from discovering it alone. Those children then judged science-fair posters as well as the few who had discovered it themselves.
For a Class 8 student, the lesson is simple: you do not have to stumble on good experimental design by luck. Learn the rule, then practise it on real questions.
Worked example: a fair test with puris (sample numbers)
Question: does oil temperature change how fast a puri puffs? This must be done with an adult in charge of the hot oil.
What you change: oil heat, at three settings: warm, hot and very hot.
What you keep the same: the same dough, rolled to the same thickness and size, dropped in the same way.
What you measure: whether it puffs within 60 seconds, and the time to puff.
Repeat: three puris at each setting.
Here are sample readings, made up to show the method:
Warm oil: none of the three puffed within 60 seconds.
Hot oil: 14 s, 12 s and 13 s. Average = (14 + 12 + 13) ÷ 3 = 39 ÷ 3 = 13 s.
Very hot oil: 7 s, 5 s and 6 s. Average = 18 ÷ 3 = 6 s.
With these numbers, hotter oil gave faster puffing, and warm oil gave none at all. Because only the oil changed, that conclusion is fair. Repeating each setting three times shows the results are steady, not a fluke.
Now a confounded version: a thick puri in hot oil and a thin puri in very hot oil. If the thin one puffs faster, was it the thinness or the heat? You cannot tell.
Which mistakes do students make?
Changing two things at once, as above.
Doing one trial. A single reading can be a fluke; repeat and average.
Recording only what you expected. Note surprises too, such as a puri that puffs on one side only.
Mixing up what you change and what you measure. Write them as two separate lists before you start.
Stopping at the answer. The chapter suggests asking the next question: does pricking a hole change the result?
A routine to use all year
Keep a question notebook. The chapter invites you to write your own question on the first page; add one each week.
For each chapter, plan one small test using the four lists: question, change, keep the same, measure.
Repeat each reading three times and write the average.
Write one line on what the result means and one new question it raises.
If a term in a later chapter, such as particle or solution, is unclear, the Fermi Concept Library covers every concept in physics, chemistry, biology, mathematics and computing. For the earlier steps in this journey, read our guides to the Class 6 opening chapter and the Class 7 opening chapter.
This week, pick one kitchen question and write its four lists before you test anything.
