Question

5 examples of heat fusion in physics with complete solution

Answer 1

Example 1

A piece of metal at 20oC has a mass of 60g. When it is immersed in a current of steam at 100∘C, 0.5g of steam is condensed on it. Determine the specific heat of metal, given that the latent heat of steam = 540 cal/g.

Solution:

Let c be the specific heat of the metal.

Heat gained by the metal

= m c Δt

= 60 × c × (100 – 20)

= 60 × c × 80 cal

Heat given by steam = mL = 0.5 × 540 cal

By the principle of mixtures,

Heat given is equal to Heat taken

0.5 × 540 = 60 × c ×80

c = 0.056 cal/g ∘C.

Example 2

Calculate the result if 64500 calories of heat are extracted from 100 g of steam at 100∘C. Latent heat of ice and steam are given as 80 cal/g and 540 cal/g respectively.

Solution:

If the full steam is converted into the water at 100∘C, then the temperature of water falls from 100∘C to 10∘C and then a part of water at 0∘C is turned into ice.

If the water converted into ice = mg

The heat gained to bring the steam at 100∘C to water at 100∘C = mL steam

= 100 × 540 cal

= 54000 cal.

The heat gained to bring water at 100∘C into water at 0∘C

= 100 × 1 × (100-0)

= 10000

 The total heat extracted,

= 54000 + 10000

= 64000 cal.

Heat still remained

= 64500 – 64000

= 500 cal.

Amount of water converted to ice,

m = Q / L

= 500 / 80

= 6.25g.