Answer: 157.5 J
Step-by-step explanation:
To calculate the amount of energy used to heat the iron, we need to use the formula:
Q = m * c * ΔT
Where:
Q = the amount of energy used (in Joules)
m = the mass of the iron (in grams)
c = the specific heat capacity of iron (in J/g °C)
ΔT = the change in temperature (in °C)
Substituting the given values, we get:
Q = 20.7 g * 0.449 J/g °C * (82°C - 99°C)
Q = 20.7 g * 0.449 J/g °C * (-17°C)
Q = -157.5 J
Note that the negative sign indicates that the iron lost energy (in the form of heat) as it cooled down.
Therefore, the amount of energy used to heat the iron from 99°C to 82°C is 157.5 J.