Recall the equation relating an object's change in thermal energy to its change in temperature:
ΔQ = mcΔT
ΔQ is the change in thermal energy.
m is the mass of the object.
c is the object's specific heat.
ΔT is the object's change in temperature.
Given values:
m = 0.5 kg = 500g
ΔT = (7-0)⁰C = 7°C
Online sources say the specific heat of silver is 0.240 J/g⁰C
Substitute the terms in the equation with the given values and solve for ΔQ:
ΔQ = 500×0.240×7
ΔQ = 840 J