Temperature and Phase Changes 5*10^6 J heat is removed from steam at 100 degree.
ID: 1489299 • Letter: T
Question
Temperature and Phase Changes 5*10^6 J heat is removed from steam at 100 degree. If there is 1.8kg of steam what is the final condition of it? Water is at 12 degree C with m= 3kg when a 1 kg piece of lead is dropped into it. If the lead is at 212 degree C what is the final temperature of both? 2kg of hot what (Ti=90 degree C is poured over a unknown material (Ti=5 degree C). The unknown melts to a liquid where the final temparature of everything is 20 degree C. The specific heat of the unknown is found to be 2000 J/Kg degree C. If there is 3Kg of the known what is the latent heat of fusion for it? A 7Kg box ides down a hill that is 3 m high where there is no friction. It then slides across a piece of aluminum where it comes to a stop. If all the energy was turned into heat what is the temperature rise of the aluminum? During long distance race, a runner loses 5 liters of water (1L + .001M^3) due to sweating. If all the sweat evaporates how much energy is transferred in the process? Where does the energy come from? What cools down? Assume the density of water is 1000kg/m^3.Explanation / Answer
Sweat is made up 99% of water, as specific heat of water is one of the highest nature, the heat need to cooling water
Q1 = m Ce Delt T
m = 5 Kg d = m/V m = d V = 1000 5 0.001 = 5 Kg
Ce = 4186 J/KG ° C
Delt T = 37-Tambiente 37°C human body temperature
Tambient Temperatura Ambient T = 25 ° C
Delt T = 37-25 = 12 ° C
Q1 = 5 4186 12 = 251160 J = 2.5 105 J
This heat must be absorbed in the body of the man, in addition then needs to evaporate the water, for which energy is needed through latent heat
Q2 = m L
L = 2257 J/Kg
Q2 = 5 2257 = 11285 J = 1.1 104 J
Elements dissolved in water will help lower the temperature of evaporation, but primarily heat loss is due to high specific heat of water. The aborvido of the body heat is
Qt = Q1 + Q2 Qt = 2.5 105 + 0.11 105 = 2.6 105 J
This expression see ordered most gives energy to sweat temperature decrease to room temperature.
Power is taken from the skin of the person that cools and by thermal conduction cool internal pairs of the body.
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