How much heat is absorbed by 100 g of water when its temperature decreases from 25oC to 5oC? (Heat capacity is 4.2 J/g K)
Correct answer: D. -8400
- A. 84,000 J
- B. -2000/4.2 J
- C. 2000/4.2 J
- D. -8400
Explanation
To calculate the heat absorbed by a substance, we can use the formula:q = m * C * ΔTWhere:q is the heat absorbed or released,m is the mass of the substance,C is the specific heat capacity of the substance, andΔT is the change in temperature.In this case, we are calculating the heat absorbed by 100 g of water when its temperature decreases from 25°C to 5°C, and the specific heat capacity of water is given as 4.2 J/g·K.ΔT = (Final temperature - Initial temperature) = (278 - 298°C) = -20KNote: The change in temperature is negative because the water is decreasing in temperature.Now we can plug in the values into the formula:q = 100 g * 4.2 J/g·K * (-20K)q = -8400 JThe negative sign indicates that heat is being released or lost by the water. Therefore, 100 g of water releases 84,00 J of heat when its temperature decreases from 25°C to 5°C.
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About Thermal Equilibrium and Heat
Thermal equilibrium means that bodies in contact have the same temperature and no net heat flows between them. The topic distinguishes heat from temperature, uses the zeroth law of thermodynamics, and covers heat transfer, specific heat capacity, thermal expansion and the conditions for reaching equilibrium.
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