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

Calorimetry Numerical Question: 13 [ Reference: Selina Class 10 ICSE physics book exercise]

1.0 kg of water is contained in a 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 = 4.2 J g-1 K-1.

Solution:

Specific heat capacity of water = 4.2 J g-1 K-1 = 4200 J Kg-1 K-1

Heat energy contained by water = m c △t =1× 4200 × 75

Heat energy = Power × time ……………………[1]

P = 1.25 kW = 1250 W

1× 4200 × 75 = 1250 × time

time = (1 × 4200 × 75) / 1250

=>time = 315000 / 1250

=>time = 252 sec

=>time = 4 min 12 sec