Question

1.0 kg of water is contained in 1.25 kW kettle. Calculate the time taken for the temperature of water to rise from 25°C to its boiling point 100°C . Specific heat capacity of water.

Answer 1

Let the time taken is t

heat loss by kettle = heat gain by water
1.25 × 10³ × t = Q = mC∆T
C is the specific heat capacity of water e.g., C = 42J/Kg/K
∆T = (100 - 25)°C
1250 × t = 1 × 4200× ( 100 - 25)
1250 × t = 4200 × 75
50t = 12600
t = 1260/5 = 252 sec

hence, time taken = 252 sec

Answer 2

Hey there!

Heat energy required for 1 kg of water to raise its temperature from 25°C to 100°C = mCΔt

here,

m = 1 kg = 1000 g

C = 4.2 J/( g . K)

Δt = 100° - 25° = 75°

Heat required = 1000 * 4.2 * 75 = 315000 J

Now,

Power = 1.25 kW = 1250 W

Power = Heat / time

1250 = 315000 / t

t = 315000 / 1250

t = 252 sec

t = 252 / 60 minute

t = 4.2 min

t = 4 min 2 sec