A phulka swells because direct flame heats the dough, turning moisture into steam. The steam expands inside, inflating the roti like a balloon while the outer layers cook and trap the steam inside.
Class 8 Science Curiosity Textbook Chapter 1 Exploring the Investigative World of Science question answer
Class 8 Science Curiosity Grade 8 Chapter 1 Exploring the Investigative World of Science solutions
When a phulka is placed on direct flame, the heat rapidly turns water in the dough into steam. Since the outer layers are partly cooked, the steam gets trapped inside, pushing the layers apart and making the phulka puff like a balloon. This shows how heat transforms water into gas, creating internal pressure that changes the roti’s shape. It’s a simple kitchen process with deep science behind it involving states of matter and pressure.
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