case study based on the chapter “Matter in Our Surroundings” (Class 9 Science), along with related questions:
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Case Study:
Riya observed that during the summer season, water kept in an earthen pot (matka) remains cooler than water in a steel container. She also noticed that when her mother sprinkled water on the rooftop in the evening, the surroundings felt cooler. Meanwhile, her brother was boiling water in the kitchen, and she noticed steam escaping from the pot and disappearing into the air.
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Based on the above case, answer the following questions:
Q1. Why does water kept in an earthen pot remain cool even in hot summer?
Q2. What is the reason behind the cooling effect when water is sprinkled on the rooftop?
Q3. What process is involved when steam disappears into the air?
Q4. What property of matter is shown when water changes to steam?
Q5. Which of the following statements is not true? (a) Evaporation causes cooling
(b) Steam is a gaseous state of water
(c) Water kept in steel container evaporates faster than in an earthen pot
(d) Particles of matter have spaces between them
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Answer Key:
A1. Water in an earthen pot remains cool due to evaporation. The porous surface allows water to seep through and evaporate, using the heat from the water, thus cooling it.
A2. Sprinkling water on the rooftop leads to evaporation. This process absorbs heat from the surroundings, causing a cooling effect.
A3. The process is diffusion of steam (gas) into air, after condensation turns it back to water droplets that evaporate again.
A4. It shows the change of state of matter (liquid to gas), specifically evaporation and boiling.
A5. (c) is not true. Water in an earthen pot evaporates faster than in a steel container due to its porous nature.
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