A molten metal of mass 150 g is kept at its melting point 800oC. When it is allowed to freeze at the same temperature, it gives out 75000 J of heat energy.

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A molten metal of mass 150 g is kept at its melting point 800^oC. When it is allowed to freeze at the same temperature, it gives out 75000 J of heat energy.

Calorimetry | Class 10 | ICSE | Physics | Selina

A molten metal of mass 150 g is kept at its melting point 800^oC. When it is allowed to freeze at the same temperature, it gives out 75000 J of heat energy.

(a)What is the specific latent heat of the metal?

(b) If the specific heat capacity of metal is 200 J kg^-1K^-1, how much additional heat energy will the metal give out in cooling to – 50^oC?

Solution:

According to the question, mass of metal = 150 g

and the specific latent heat of metal is

L = Q / m = 75000 / 150

Therefore, L = 500 J g^-1

and the specific heat capacity of metal is 200 J kg^-1 K^-1

In this case, the change in temperature = 800 – (-50) = 800 + 50

= 850⁰ C (or 850 K)

We know that the expression for heat energy is given by => △Q = mc△T

△Q = 0.15 × 200 × 850 = 25500 J

i

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