*Solution:*

Cp = 4.19 KJ/(kg·C)

This is the specific heat of water at 15 °C and 101.325 kPa atmospheric pressure.

This is the amount of energy required to raise the temperature of 1 kg ( 1 Liter ) of water by 1 °C.

Density of water:

Density of water:

1 kg/Liter

1000 kg/cubic meter

1 metric ton/cubic meter

1 g/cubic centimeter

1 g/ml

Boiling water for coffee/tea:

Boiling water for coffee/tea:

1 Liter is approximately 4 cups (good for a family of four)

100 °C is the boiling point of water at a pressure of 1 atm (101.325 kPa)

Temperature of cold tap water and hot water:

Temperature of cold tap water and hot water:

cold tap water is around 15 °C

in most homes, hot water heaters are set at 60 °C (140 °F)

Heat Calculation Formula:

Heat Calculation Formula:

Q = m x Cp x (T2-T1)

where:

Q = heat energy required to boil water, KJ

m = mass of water, kg

Cp = specific heat of water, 4.19 KJ/(kg·C)

T2 = boiling point of water, 100 C

T1 = temperature of cold tap water, 15 C

Q = 1 kg x 4.19 KJ/(kg·C) x (100 C - 15 C)

Q = 357 KJ

Black and Decker Kettle Power Rating:

Black and Decker Kettle Power Rating:

1500 watts heating power

1500 watts is equal to 1.5 KW (KJ/sec)

Time to boil 1 Liter (1 kg) of water from 15 C:

Time to boil 1 Liter (1 kg) of water from 15 C:

assuming no heat is lost,

time = Q/Power of kettle

time = 357 KJ/1.5 KJ per second

time = 238 seconds

time = 4 minutes

Note: under the same conditions,

Note: under the same conditions,

a. boiling 2 Liters of water would double the time to boil --> 8 minutes

b. using twice the kettle power (3000 watts) requires only half the boiling time --> 2 minutes

Time to raise 1 Liter of water 1 degree Celsius

Time to raise 1 Liter of water 1 degree Celsius

using the same 1500-watt kettle, and assuming no heat loss

Q = 1 kg x 4.19 KJ/(kg·C) x (1 C)

Q = 4.19 KJ

time = 4.19 KJ/1.5 KJ per second

time = 3 sec

Note:

Note:

The time required to raise the temperature of water 1 degree C is dependent on,

a. amount (mass) of water

b. power rating of kettle

your missing the energy required to make the phase change. this only gets the water to 100 liquid...

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