Calculate heat transfer and temperature changes using the fundamental equation q = mcΔT
Heat Equation: q = mcΔT
Calculate heat absorbed or released during temperature changes
grams (g)
J/(g·°C)
°C
°C
Calorimetry measures heat transfer during physical and chemical processes using the relationship between heat energy, mass, specific heat, and temperature change.
q = mcΔT
q > 0 (Positive)
Heat absorbed, endothermic
Temperature increases
q < 0 (Negative)
Heat released, exothermic
Temperature decreases
Problem:
How much heat is required to raise the temperature of 250 g of water from 20°C to 100°C? (cwater = 4.184 J/(g·°C))
Given:
m = 250 g
c = 4.184 J/(g·°C)
Ti = 20°C, Tf = 100°C
Calculate ΔT:
ΔT = 100 - 20 = 80°C
Apply q = mcΔT:
q = (250)(4.184)(80)
q = 83,680 J = 83.7 kJ
Result:
83.7 kJ of heat is required. This is endothermic (q > 0) because temperature increases.
Specific heat is the energy needed to raise 1 g by 1°C:
| Substance | c (J/(g·°C)) |
|---|---|
| Water (l) | 4.184 |
| Ice | 2.09 |
| Steam | 2.01 |
| Ethanol | 2.44 |
| Aluminum | 0.897 |
| Copper | 0.385 |
| Iron | 0.449 |
| Gold | 0.129 |
Water has one of the highest specific heats, making it excellent for temperature regulation.