Probe and Ponder
Q1. Why is one side of a puri thinner than the other?
Answer:
This is a question to spark curiosity. The chapter suggests that when a puri is fried in hot oil, the dough expands due to the rapid production of steam from the moisture inside. The side that is in contact with the hot oil first becomes crispy and sets before it can puff up fully, while the other side (which may be exposed to oil later or less directly) puffs up more, resulting in a thinner side. However, the chapter also mentions that even this simple phenomenon is not completely understood by scientists today, encouraging further investigation. Factors like the thickness of the dough, the temperature of the oil, and the way the puri is dropped into the oil all play a role.
Q2. Are there more grains of sand on all the beaches and deserts of the world, or more stars in our galaxy?
Answer:
This is a question designed to spark wonder and curiosity. Scientific estimates suggest that the number of stars in our galaxy (the Milky Way) is roughly 100 billion to 400 billion. The total number of grains of sand on all the beaches and deserts of the world is estimated to be around 7.5 x 10^18 (7.5 quintillion). This number is far greater than the number of stars in our galaxy. So, there are more grains of sand on Earth than stars in our galaxy.
Let's Explore
Q1. Is there such a question that makes you curious about the world? Write it here!
Answer:
This is a personal reflection question. Students are encouraged to write down a question that sparks their curiosity about the world. Examples include: "Why do we dream?", "What causes earthquakes?", "How do plants make their food?", or "Why is the sky blue?"
In-Text Activities
Q1. To help you think like a scientist, let us go back to a question we asked on the first page: Why is one side of a puri thinner than the other? Firstly, remember that science is everywhere! You don't need a fancy laboratory to do simple experiments. Even your kitchen at home is a wonderful place to observe and ask questions. All you need is to start with curiosity, careful observation, and asking what happens if...? Have you noticed how a puri or a batura puffs up when placed in hot oil? Or how a phulka swells when put directly on the flame. Why does it puff up like a balloon? And why is one side thinner than the other? These are questions a scientist might ask—and you can too! Let's see how we can investigate this simple everyday phenomenon like a scientist would. First, we will try to ask a scientific question. What are the different things that may change the way a puri puffs up when fried? To answer this, we may want to do some simple experiments. For that, we try and find out two main things—what all can we change or control when we do the experiment, and what all can we observe to see if these changes made any difference. In this case, we can perhaps think of changing the thickness and the size of the rolled dough. We could also try to use different types of flour (atta, maida, etc.). While frying the puri, we can also change the temperature of the hot oil, or try and drop the rolled dough into the oil in different ways (drop it vertically? slide it at an angle? slide it slowly?) Notice that these are things that we can control. However, to make sense of the changes, we also need to think of what we can observe or measure. Some of these may have just yes/no answers, in some cases there might be a number we can measure. Maybe we can start by checking whether the puri puffs up (yes/no), or we can measure the time it takes to puff up (seconds). We can check whether a very thick layer of dough still gives a thin side to the puri. Further, while doing such experiments, it is better to change only one thing at a time while keeping the other conditions same. For example, if we wanted to see the effect of boiling hot, hot, and not very hot oil, we would use circles of dough of the same thickness, and drop them in the same way. It is also a good idea to keep notes of everything that you see and sense when doing an experiment. Did the oil splatter, smell, or smoke? And after doing one round of experiments, you may think of more questions. Do puris puff better when made fresh or from stored dough? What happens if I prick a hole in the puri before frying? This is exactly how all scientific experiments, from simple to the most complicated are done. This is the idea of systematic investigation. And just so you know, even this simple everyday observation—of a puri puffing—is not really completely understood by scientists today! So, whether it is the puffing of a puri or the shrinking bright part of the Moon after purmina, let your careful observations guide you along your explorations into the investigate world of science.
Answer:
Activity: Investigating the Puffing of a Puri
This activity encourages students to think like scientists. The key steps are:
- Ask a Scientific Question: What affects the way a puri puffs up when fried?
- Identify Variables (Things to Change/Control):
- Thickness of the rolled dough
- Size of the dough circle
- Type of flour (atta, maida)
- Temperature of the oil
- Way the dough is dropped into the oil (vertically, at an angle, slowly)
- Freshness of the dough
- Whether a hole is pricked in the puri
- Identify Observations/Measurements:
- Does the puri puff up? (Yes/No)
- Time taken to puff up (seconds)
- Is one side thinner than the other? (Yes/No)
- Color and texture of the puri
- Did the oil splatter, smoke, or smell?
- Conduct Experiments Systematically: Change only one variable at a time while keeping all other conditions the same. For example, to test the effect of oil temperature, keep the dough thickness and size the same, and drop the puris in the same way, but use oil at different temperatures.
- Record Observations: Keep a notebook to record everything you observe and sense during the experiment.
- Draw Conclusions: Analyze your observations to see what factors make a puri puff up better or result in a thinner side.
- Ask New Questions: Based on your findings, think of new questions to investigate (e.g., "Does adding a little sugar to the dough change anything?").
This is exactly how systematic scientific investigation works—through careful observation, controlled experimentation, and recording results.