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Burns produced by steam at 100°C are much more severe than those produced by the same mass of 100°C water. To verify this, do the following.

Calculate the heat (in kcal) that must be removed from 6.00 g of 100°C water to lower its temperature to 52.0°C.
Calculate the heat (in kcal) that must be removed from 6.00 g of 100°C steam to condense it and lower its temperature to 52.0°C.
Calculate (in kg) the mass of human flesh that the heat produced in each case can raise from the normal 37.0°C to 52.0°C. (Flesh is badly damaged at 50.0°C.)
steam ____________ kgwater kg

User Dheinz
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1 Answer

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Final answer:

The heat that must be removed from 6.00 g of 100°C water to lower its temperature to 52.0°C is -292 kcal. The heat that must be removed from 6.00 g of 100°C steam to condense it and lower its temperature to 52.0°C is 32.7 kcal. The mass of human flesh that the heat produced in each case can raise from 37.0°C to 52.0°C is 20.5 kg for water burn and 2.3 kg for steam burn.

Step-by-step explanation:

To calculate the heat that must be removed from 6.00 g of 100°C water to lower its temperature to 52.0°C, we can use the equation Q = mcΔT, where Q is the heat, m is the mass, c is the specific heat capacity, and ΔT is the temperature change. The specific heat capacity of water is 1 cal/g °C, which is equivalent to 1 kcal/kg.°C. Therefore, the heat transfer for the water can be calculated as:

Qwater = (6.0 g)(1 kcal/kg.°C)(52°C - 100°C) = -292 kcal

To calculate the heat that must be removed from 6.00 g of 100°C steam to condense it and lower its temperature to 52.0°C, we can use the equation Q = mL, where Q is the heat, m is the mass, and L is the latent heat of vaporization. The latent heat of vaporization for steam is 22.6 kJ/g. Therefore, the heat transfer for the steam can be calculated as:

Qsteam = (6.0 g)(22.6 kJ/g) = 136.8 kJ = 32.7 kcal

The heat produced in each case can be used to raise the temperature of human flesh from 37.0°C to 52.0°C. To calculate the mass of human flesh, we can use the equation Q = mcΔT, where Q is the heat, m is the mass, c is the specific heat capacity of flesh, and ΔT is the temperature change. Assuming the specific heat capacity of the flesh is 0.83 kcal/kg.°C:

Mass of flesh for water burn = (292 kcal) / (0.83 kcal/kg.°C)(52.0°C - 37.0°C) = 20.5 kg

Mass of flesh for steam burn = (32.7 kcal) / (0.83 kcal/kg.°C)(52.0°C - 37.0°C) = 2.3 kg

Therefore, the heat produced by steam can raise a smaller mass of flesh to a higher temperature, resulting in more severe burns compared to the same mass of water at the same temperature.

User Mohsen Saremi
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