Two Basic Questions:
1. A kettle holding 1lt. of water is boiling. Assuming water is evaporating at a constant evaporation rate of 1g/min, determine how long it will take for the kettle to dry out.
2. Another kettle holding 1lt. of water and 20g. of salt is also boiling. Again water evaporates at a rate of 1g/min. This time you are asked to derive a mathematical relationship for how the salt concentration in the kettle changes with respect to time.
Starting from these two basic questions, we can discuss some basic topics of Thermdynamics, exactly conservation of mass and energy. These two questions are about material balance in open and closed systems.