Tuesday, February 17, 2009

Which will feel hotter to touch: holding 10.0 g of aluminum at 95 degrees Celsius, or 10 g of lead at the same temperature? Assume each material is...

The substance that will release more heat as it cools down from 95 degrees Celsius to the skin temperature of 34 degrees Celsius will be hotter to touch. We can calculate the amount of heat released for each of the two materials, aluminum and lead, using specific heat capacity. The amount of heat required to raise the temperature of 1 gram of a substance by 1 degrees Celsius is known as its specific heat capacity. The specific heat capacities of aluminum and lead are 0.9 J/gm/K and 0.128 J/gm/K. Since the specific heat capacity of lead is less than aluminum, it will release less heat as it cools down.


We can also calculate the amount of heat released as the materials cool down by using the following equation:


Heat released = mass of substance x specific heat capacity x change in temperature


Heat released in the case of aluminum = 10 g x 0.9 J/g/K x (95 - 34) C = 549 J


Heat released in the case of lead = 10 g x 0.128 J/g/K x (95-34) C = 78.08 J


Thus, aluminum will release more heat than lead when it is held until it reaches the skin temperature. And it will feel hotter to touch as compared to lead.

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