Question

A kettle used at a building site is filled with 25 liters of water at 16°C. The water is heated until it reaches 90°C. Calculate the amount of heat required in KJ

Answer 1

Given:

A kettle used at a building site is filled with 25 liters of water at 16°C. The water is heated until it reaches 90°C.

To find:

Heat required in kJ.

Calculation:

General expression for heat required for change in temperature of a body:

$\boxed{ \sf{H = m \times c \times \Delta \theta}}$

[m is the mass , c is the specific heat capacity whose value is approx 4.2 J/g °C]

Putting available values:

$= > \sf{H = (25 \times 1000) \times 4.2\times (90 - 16)}$

$= > \sf{H = 25000\times 4.2 \times (90 - 16)}$

$= > \sf{H = 25000\times 4.2 \times 74}$

$= > \sf{H =7770 \times {10}^{3} \: joule}$

$= > \sf{H =7770 \:kilo joule}$

So, final answer is:

$\boxed{\sf{H =7770 \:kilo joule}}$

Answer 2

The amount of heat required is H = 7770 KJ

Explanation:

We are given that:

• Amount of water = 25 liters
• Temperature = 16°C

Solution:

The formula is given below

H = m x c x Δθ

Here

• M = mass
• c = specific heat

The value of specific heat is approximate = 4.2 J/g  

Now put the values in the formula:

H = [ 25 x 1000] x 4.2 x (90 - 16)

H = 2500 x 4.2 x 74

H = 7770 x 10^3 Joules

H = 7770 kJ