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प्रश्न
Give scientific reasons for the following:
Bottled drinks are cooled more effectively when surrounded by lumps of ice than by cold water at 0°.
उत्तर १
Lumps of ice cool better than cold water because each gram of ice requires additional 80 calories of heat to get converted into water. Hence, cooling capacity of lumps of ice is more than cold water.
उत्तर २
Every 1 kg of ice at 0°C absorbs 336,000 J of heat energy to form water at 0°C. As ice can extract 336,000 J of heat energy, more than water at 0°C, therefore it cools the bottled drinks more effectively.
संबंधित प्रश्न
Name the law on which the principle of mixture is based.
A piece of iron of mass 2.0 kg has a heat capacity of 966 J K-1. Find heat energy needed to warm it by 15°C.
1 kg of ice at 0°C is heated at a constant rate and its temperature is recorded after every 30 s till steam is formed at 100℃. Draw a temperature time graph to represent the change of phase.
The melting point of naphthalene, a crystalline solid is 80℃ and the room temperature is 30℃. A sample of liquid naphthalene at 100℃ is cooled down to the room temperature. Draw a temperature time graph to represent this cooling.
A bucket contains 10 liters of water at 80°C. Cold water at 25°C is run from a tap into the bucket of hot water for 20 seconds and the temp. Of the water in the bucket falls to 50°C.
(a) Calculate the rate at which cold water came out of the tap.
(b) State an assumption made in the above calculation.
40 g of ice at -16°C is dropped into water at 0°C, when 4 g of water freezes into ice. If specific heat capacity of ice is 2100 J/kg°C, what will be the latent heat of fusion of ice?
Ice is more effective in cooling than the ice-water. Explain.
State two impacts of global warming on the life on earth.
A copper calorimeter of mass 50g contains 100g of water at 20°C. A metallic piece of mass 250 g is heated to 100°C and is then dropped into the calorimeter. The contents of the calorimeter are well stirred and its final highest temperature is recorded to be 28 °C. If the specific heat capacity of water is 4.2 J/g°C and of copper is 0.4 J/g°C, find:
(i) the heat gained by water,
(ii) the heat gained by calorimeter,
(iii) total heat supplied by the metal piece, and
(iv) the specific heat capacity of metal.
