re-Lab Questions strange reason, you place a block of cement and a block of wood
ID: 552424 • Letter: R
Question
re-Lab Questions strange reason, you place a block of cement and a block of wood near a fire. Which will feei the hottest after five minutes? Explain 1. For some strange reason, Ya material rplacing an unknown material in 50g of water, the temperature of the water increases from 23.0°C to 25.1, what is the amount of heat that was absorbed by the water? 3. If in the previous problem 24g of the unknown material was added to the water at an initial temperature of 963°C, what was the mystery material?Explanation / Answer
1) The heat capacity of a substance is defined as the amount of heat energy needed to raise the temperature of 1 g of the substance by 1°C. Cement has a lower heat capacity as compared to wood. Consequently, for the same amount of heat energy supplied to the same masses of cement and wood for the same time, cement will show a higher rise in temperature. Therefore, cement will get hotter than wood.
2) Mass of water = 50 g; temperature change of water = (25.1 – 23.0)°C = 2.1°C.
The heat capacity of water is 1 cal/g.°C.
Heat energy gained by the water = (mass of water)*(heat capacity of water)*(temperature change of water) = (50 g)*(1 cal/g°C)*(2.1 °C) = 105 cal (ans).
3) Mass of the mystery material = 24 g; initial temperature of the material = 96.3°C; therefore, change in temperature of the material = (96.3 – 25.1)°C = 71.2°C.
As per the principle of thermochemistry,
(24 g)*(S)*(71.2°C) = 105 cal (S = heat capacity of the material)
====> 1708.8*S g.°C = 105 cal
====> S = (105/1708.8) cal/g.°C = 0.0614 cal/g.°C.
Next look up a table of materials where the heat capacity values are listed.
The heat capacity value matches that of cadmium, charcoal and palladium. Out of these three, charcoal (coal) is a common material encountered easily and the mystery material is most likely charcoal.
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