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प्रश्न
Explain the following
Fishes survive in ponds even when the atmospheric temperature is well below 0°C.
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उत्तर
The anomalous expansion of water helps preserve aquatic life during very cold weather. When temperature falls, the top layer of water in a pond contracts becomes denser and sinks to the bottom. A circulation is thus set up until water in the pond reaches its maximum density at 4°C. If the temperature falls further, then the top layer expands and remains on the top till it freezes. Thus, even though the upper layer are frozen, the water near the bottom is at 4°C and the fishes can survive in it easily.
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संबंधित प्रश्न
Calculate the time required to heat 20 kg of water from 10°C to 35°C using an immersion heater rated 1000 W. Assume that 80% of the power input is used to heat the water. Specific heat capacity of water = 42000 J kg−1 K−1.
Consider the situation of the previous problem. Assume that the temperature of the water at the bottom of the lake remains constant at 4°C as the ice forms on the surface (the heat required to maintain the temperature of the bottom layer may come from the bed of the lake). The depth of the lake is 1.0 m. Show that the thickness of the ice formed attains a steady state maximum value. Find this value. The thermal conductivity of water = 0.50 W m−1°C−1. Take other relevant data from the previous problem.
A calorimeter contains 50 g of water at 50°C. The temperature falls to 45°C in 10 minutes. When the calorimeter contains 100 g of water at 50°C, it takes 18 minutes for the temperature to become 45°C. Find the water equivalent of the calorimeter.
Explain the following
A hollow glass sphere which floats with its entire volume submerged in water at 4°C, sinks when water is heated above 4°C.
Explain the following
A glass bottle completely filled with water and tightly closed at room temperature is likely to burst when kept in the freezer of a refrigerator.
Give reasons for the following:
Even when the water in the lakes is frozen, fish can survive.
Write the name.
The instrument used to study anomalous behaviour of water.
Observe the following diagram and write the answers to the questions given below.
- Which process does the graph represent?
- What is the range of temperature responsible for the behaviour?
A graph between the volume and temperature of water is shown. Explain the anomalous behaviour of water.
