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.
Last updated
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.
Practise Thermodynamics
714 free Thermodynamics MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Physics questions like this
Physics is on 13 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
Related questions
100 W heater is switched on for 5 minutes to melt ice. What is the mass of ice that melts at 0oC? ( The specific latent heat of fusion of ice is 334 J/g).
100 W heater is used for 5 minutes to heat 500 g of water. What is the change in the temperature of the water? (The specific heat capacity of water is 4.2 J/gC).
100 W heater is used to melt 50 g of ice at 0°C. How long should the heater be switched on? (Specific latent heat of fusion of ice is 334 J/g)
100 W heater is used to melt 50 g of ice at OC. How long should the heater be switched on? (Specific latent heat of fusion of ice is 334 J/g)
100W heater is used for 5 minutes to heat 500g of water. What is the change in the temperature of water? (Specific heat capacity of water is 4.2 J/gC)