A cup of rather dilute hot tea initially at 140 degrees F is served to a customer at Howard Johnson's. Unfortunately, before they get around to drinking it, it has spontaneously cooled off to 100 degrees F. Suppose that our customer complains about the cold tea and is given a second cup of hot tea. Feeling especially hungry (for tea?) they mix the hot tea and the cold tea together so that they will have twice as much tea (albeit luke warm). Assuming that the mixing occurs spontaneously and adiabatically, what is the final temperature of the tea, the change in entropy of the tea, and the change in entropy of the universe for the mixing process? The temperature of the restaurant (the surroundings) is 70 degrees F. The tea has a mass of 200g.
Energy transfer
The flow of energy from one region to another region is referred to as energy transfer. Since energy is quantitative; it must be transferred to a body or a material to work or to heat the system.
Molar Specific Heat
Heat capacity is the amount of heat energy absorbed or released by a chemical substance per the change in temperature of that substance. The change in heat is also called enthalpy. The SI unit of heat capacity is Joules per Kelvin, which is (J K-1)
Thermal Properties of Matter
Thermal energy is described as one of the form of heat energy which flows from one body of higher temperature to the other with the lower temperature when these two bodies are placed in contact to each other. Heat is described as the form of energy which is transferred between the two systems or in between the systems and their surrounding by the virtue of difference in temperature. Calorimetry is that branch of science which helps in measuring the changes which are taking place in the heat energy of a given body.
As the mixing process is adiabatic, no heat is lost to the surroundings.
So, , where is the change in enthalpy.
Enthalpy , where
m is the mass
is the specific enthalpy.
Here, as the values for tea is not given, we consider the values for water instead.
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