Question

Q.3) A hot 1 kg chunk of copper is allowed to cool to 100°C. If the copper gave off 231 kJ of energy, what was the initial temperature of the copper? The specific heat of copper is 0.385 J/g°C.​

Answer 1

Given info : A hot 1 kg chunk of copper is allowed to cool to 100°C , if the copper gave off 231 kj of energy.

To find : the initial temperature of the copper is ..

solution : we know, heat, Q = msΔT

where m is mass of substance, s is specific heat of substance and ΔT is the change in temperature.

here, Q = -231 kJ = -231 × 10³ J [∵ energy is released so we should take it negative. ]

m = 1 kg = 1000g

s = 0.385 J/g/°C

ΔT = ( 100°C - T)

∴- 231 × 10³ J = 1000g × 0.385 J/g/°C × (100°C - T)

⇒ -231/0.385 = 100°C - T

⇒ -600°C  = 100°C  - T

⇒T = 700°C

therefore the initial temperature of the copper is 700°C.