Worked Example
Question: How much energy does it take to heat 1 L of water from 10oC to 100oC?
To answer this question we need to know the specific heat capacity of liquid water (4.184 J·g-1·K-1) as well as the formula that describes energy flow and a change in temperature, Q=mcΔT. Q represents the heat energy, measured in Joules; m represents the mass; c represents the specific heat capacity; and ΔT represents the change in temperature, measured in Kelvin.
Q=mcΔT
Q=(1000 g)(4.184 J·g-1·K-1)(90K)
Q=376.6 kJ
To put this in perspective, 376 kJ of energy would warm a similar mass of air approximately 370oC!
Your Turn
True or False: A sample of liquid water at 20oC will not evaporate.
Click here to show answer
Even though a liquid may not be boiling, it still exists in dynamic equilibrium with its surroundings. In this case, water is constantly moving back and forth across the liquid-gas interface. In most cases, if the air is not saturated with water vapour, the water will continue to evaporate until equilibrium is reached.