Chapter 6, Problem 6.1P

Interpretation Introduction

Interpretation:

The reason for the positive and negative value of heat $\left(q\right)$ and work $\left(w\right)$ when enters a system or leaves a system respectively is to be determined.

Concept introduction:

Heat $\left(q\right)$ is the energy transferred as a consequence of the difference of the temperature between the system and surrounding.

Work $\left(w\right)$ is the energy needed to move an object in the opposite direction of the force applied.

Answer to Problem 6.1P

Heat and work of the process are determined from the perspective of the system. Therefore in case of work done on the system and heat taken by the system the final energy is less as compared to initial and in case of work done on the system and heat taken by the system the final energy is more as compared to initial.

Explanation of Solution

The work done by the system and heat released by the system is negative because the final energy of the system, in this case, is less than the initial energy of the system.

The work done on the system and heat taken by the system is positive because the final energy of the system, in this case, is more than the initial energy of the system.

Heat and work are defined from the perspective of the system and hence it is positive when enters the system and negative when leaves the system.

Conclusion

The work done by the system and heat released by the system is negative and the work done on the system and heat taken by the system is positive.