95.6 cal are needed. Explanation: Use the following equation: q = m c Δ T , where: q is heat energy, m is mass, c is specific heat capacity, and Δ T is the change in temperature. Δ T = T final − T initial Known m = 125 g c Pb = 0.130 J g ⋅ ∘ C T initial = 17.5 ∘ C T final = 42.1 ∘ C Δ T = 42.1 ∘ C − 17.5 ∘ C = 24.6 ∘ C Unknown q Solution Plug the known values into the equation and solve. q = ( 125 g ) × ( 0.130 J g ⋅ ∘ C ) × ( 24.6 ∘ C ) = 400. J
(rounded to three significant figures) Convert Joules to calories 1 J = 0.2389 cal to four significant figures. 400 . J × 0.2389 cal 1 J = 95.6 cal
(rounded to three significant figures) 95.6 cal are needed.
