A 100-watt heater is used for 5 minutes to heat some water from 20 °C to 50°C. What is the mass of water that is heated? The specific heat capacity of water is 4.2 J/g°C.
Correct answer: C. 240 g
- A. 4 g
- B. 40 g
- C. 240 g
- D. 24 g
Explanation
An explanation for this question is given below: We know that P = 100W, t = 5 x 60 = 300s, T = 30 C, and c = 4.2 We will use the formula Q = mcΔT Pt = mcΔT m = Pt/cΔT m = (100x300)/(4.2x30) m = 238 g It is very close to 240g of mass, hence, we may say that 240 g of water were heated, so option C is the correct option.
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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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