Question

Hot water in an ideal thermos flask is an example for (This question may have one or more correct answers)
A. Isolated system
B. Open system
C. Closed system
D. Adiabatic system

Answer 1

The question is based on the concept of the properties of the types of systems. In the case of an isolated system, no exchange of energy and matter takes place, in an open system exchange of energy and matter takes place, in a closed system only exchange of energy takes place and in the adiabatic process, no exchange of heat and matter takes place.

Complete answer:
First, let us know the definitions of the systems given in options.
Isolated system – Neither the exchange of energy nor the exchange of the matter takes place in this type of system. The total amount of energy remains constant.
Open system – The exchange of both, that is, energy and matter take place in this type of system. The total amount of energy will be variable, as the exchange of energy and matter takes place.
Closed system – The exchange of only, that is, energy takes place in this type of system. The total amount of energy will be variable, as the exchange of energy and matter takes place.
Adiabatic system – No exchange of the heat and mass takes place between the thermodynamic system and its surrounding in this type of system.
Now consider the given example.
Neither the heat transfer nor the mass transfer takes place in the system of hot water ideal thermos flasks.
The statement in terms of the expressions is as follows,

& dm=0 \\\ & dE=0 \\\ \end{aligned}$$ This represents an isolated system. The heat remains constant inside the system of hot water ideal thermos flasks. The statement in terms of the expressions is as follows, $$dQ=\text{constant}$$ This represents an adiabatic system. As, the hot water in an ideal thermos flask is an example for the isolated and the adiabatic system., **Thus, the options (A) and (D) are correct.** **Note:** In this case, the question was a combination of systems, as in the given example, the properties of two systems were combined, such as the constant heat energy property of the adiabatic system and no exchange of the energy and the matter between the system and its surrounding property of the isolated system. Even, they can combine the properties of other systems, to confuse the students.