Equations
The heat energy associated with a change in temperature that does not involve a change in phase is given by
q=msΔT
where q is heat in joules, m is mass in grams, s is specific heat in joules per gram-degree Celsius, J/(g⋅°C), and ΔT is the temperature change in degrees Celsius. The heat energy associated with a change in phase at constant temperature is given by
q=mΔH
where q is heat in joules, m is mass in grams, and ΔH is the enthalpy in joules per gram.
Physical constants
The constants for H2O are shown here:
- Specific heat of ice: sice=2.09 J/(g⋅°C)
- Specific heat of liquid water: swater=4.18 J/(g⋅°C)
- Enthalpy of fusion (H2O(s)→H2O(l)): ΔHfus=334 J/g
- Enthalpy of vaporization (H2O(l)→H2O(g)): ΔHvap=2250 J/g
Part A:
How much heat energy, in kilojoules, is required to convert 52.0 g of ice at -18.0 °C to water at 25.0 °C ?
Express your answer to three significant figures and include the appropriate units.