Calculate change in entropy when a 3.5kW electrical immersion heater is switched on for 15s in a large tank of water at 10°C

Answer 1

We can solve for the change in entropy for the water using the equation ΔS = Q/T, where ΔS is change in entropy, Q is the heat transferred (in J), and T is the temperature (in K).

Let's assume that 3.5kW refers to the output of the heater and not the amount of power it uses.

3.5kW is equivalent to 3500W, which means the same thing as 3500 J/s. This means that it transfers 3500J each second into the water. Over 15 seconds, this is a heat transfer of 3500J/s*15s = 52500J.

Convert 10°C to Kelvin: 10°C = 283K

Now we can plug those values into the equation ΔS = Q/T

ΔS = Q/T

ΔS = 52500J / 283K = 185.5J/K