How much energy (in J) is lost when a sample of iron with a mass of 28.9 g cools from 74.0 °C to 21.0 °C?

Question

I dont understand how to do this

Answer 1

Q = m c ΔT

 

m = mass = 28.9 g = 0.0289 kg

 

ΔT = (21 - 74) degrees C = -53 degrees C

 

c = specific heat of iron, which you can find in a table of specific heats

 

c = 0.47 kJ / (kgC) = 470 J / (1000 gC) = 0.47 J/(gC)

 

Q = (28.9 g)[0.47 J/(gC)](-53 C) = -719.9 J

 

So it loses 719.9 J