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An unknown substance has a specific heat of 4.2 kJ/kg °C. How much heat would be needed to change the temperature of 15.0 kg of this substance from 56°C to 14°C? Let (+) indicate that heat is being added to the substance and (-) indicate that heat is being taken from the substance.

Respuesta :

Answer : The amount of heat needed to change the temperature of the substance would be, -2646 kJ

Explanation :

Formula used :

[tex]Q=m\times c\times \Delta T[/tex]

or,

[tex]Q=m\times c\times (T_2-T_1)[/tex]

where,

Q = heat needed = ?

m = mass of substance = 15.0 kg

c = specific heat of substance = [tex]4.2kJ/kg^oC[/tex]

[tex]T_1[/tex] = initial temperature  = [tex]56^oC[/tex]

[tex]T_2[/tex] = final temperature  = [tex]14^oC[/tex]

Now put all the given value in the above formula, we get:

[tex]Q=15.0kg\times 4.2kJ/kg^oC\times (14-56)^oC[/tex]

[tex]Q=-2646kJ[/tex]

Therefore, the amount of heat needed to change the temperature of the substance would be, -2646 kJ

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