The puri investigation

The idea

Scientific investigation starts from a focused question, tests it with simple, carefully designed trials, and uses the observations to improve understanding; working through these steps is systematic investigation.

The puffing puri

A puri dropped into hot oil puffs up like a balloon. And one side of it is thinner than the other. Why?

You want to find out. What would a scientist do first?

• Guess an answer and stop there
• Ask a small, focused question and test it
• Read the answer somewhere and never try anything

Build the investigation

Here are four steps of the puri investigation, mixed up. Tap them in the order a scientist does them.

Systematic investigation

Start from a focused question. Test it with simple, carefully designed trials. Use the observations to improve understanding. This is systematic investigation.

All scientific experiments, from the simplest to the most complicated, are done this way.

• Step | In the puri story
• Focused question | What may change the way a puri puffs?
• Simple, careful trials | Dough circles of the same thickness, dropped in the same way, into oil of different temperatures
• Observations | Does it puff? How many seconds does it take?
• Better understanding | New questions: do puris puff better from fresh dough or stored dough?

Notes

A systematic investigation starts from a focused question, tests it with simple, carefully designed trials, and uses the observations to improve understanding.

Check yourself

Which one is a focused question that we can test with trials?

Meera asks: does the amount of water change how tall a bean plant grows? Which plan is a careful trial?

Scientists say even a puffing puri is not completely understood yet. What does this tell us about investigation?

• Why is food so wonderful?. Too wide. We cannot plan a trial for it.
• Does the oil temperature change how many seconds a puri takes to puff? — correct. Yes! One thing to change (oil temperature) and one thing to measure (seconds).
• Who first made the puri?. That is a question about history. Dough and oil trials cannot answer it.
• Ask her classmates to vote for the amount of water they like best.. A vote shows opinions. A trial shows what the plants really do.
• Write "more water, taller plant" in her notebook, without growing anything.. That is a guess, not a trial. A trial needs observations.
• Give bean plants different amounts of water, keep everything else the same, and measure their heights every week. — correct. Yes. The trial is simple, planned with care, and gives observations (heights) to learn from.
• Only big, complicated things can be investigated.. No. Even an everyday puri can be investigated, and it still has puzzles.
• The scientists who tried it were careless.. Not so. Even careful trials can leave questions open.
• Investigation goes on: each answer can lead to new questions. — correct. Yes. Better understanding raises new questions, and the next round begins.