First Law Of Thermodynamics: Problem-Solving

The first law of thermodynamics states that the heat added to a system is utilized in performing the work and increasing the system's internal energy.

Consider an example where 100 grams of water at one atmospheric pressure converts into steam at 100 degrees Celsius. What is the change in the internal energy for this thermodynamic process?

This thermodynamic system changes from the initial liquid to the final gaseous state at constant temperature and pressure when water converts to steam.

The heat transfer into the system is the product of mass and the latent heat of the vaporization of water.

The work done is equal to the product of pressure and volume change. Using the value of mass and density of the steam and water, the volume change and so the work done is estimated.

Here the unknown quantity is the change in the internal energy, while the known quantities are heat supplied and work done by the system. So, applying the first law of thermodynamics, a change in internal energy can be estimated.