Question

Internal energy does not include (1) vibrational cnergy (2) rotational cncrgy (3) cnergy arising duc to gravitational pull (4) nuclear cnergy

Short answer

Energy arising due to gravitational pull and nuclear energy are not included in internal energy.

Step-by-step solution

Understand the Concept of Internal Energy

Internal energy is the total energy contained within a system, which includes kinetic energy (due to the movement of particles) and potential energy (due to the interactions between particles).

Identify Components of Internal Energy

The internal energy of a system typically includes vibrational energy, rotational energy, and energy due to intermolecular forces.

Exclude Non-Components

Internal energy does not account for energy due to external factors like gravitational pull or nuclear energy, as these energies are not part of the internal aspects of the system.

Conclusion

Given the options, the correct choice is the type of energy not included as part of internal energy.

Key concepts

Vibrational Energy

Vibrational energy is a fundamental component of internal energy in many systems. It is the energy associated with the periodic movement of molecules within a system. When molecules oscillate or vibrate, they create vibrational energy. Each molecule has specific vibrational energy levels it can occupy, depending on its nature and the forces acting on it.
Vibrational energy plays a critical role in the thermal properties of materials. For instance, when you heat a substance, some of the heat energy is converted into vibrational energy, causing the molecules to vibrate more vigorously.
In summary, vibrational energy is an internal property and contributes to the overall internal energy of a system.

Rotational Energy

Rotational energy is another key aspect of internal energy. This type of energy is associated with the rotation of molecules around their center of mass. Just like vibrational energy, rotational energy depends on the specific properties of molecules and how they interact.
Molecules can spin around various axes, and each possible way of spinning corresponds to different rotational energy levels. The faster a molecule spins, the higher its rotational energy.
Rotational energy is especially important in gases, where molecules have more freedom to rotate, contributing significantly to the internal energy and affecting the gas's overall temperature.

Nuclear Energy

Nuclear energy is the energy stored in the nucleus of an atom. Unlike vibrational and rotational energy, nuclear energy is not considered part of a system's internal energy in most contexts. This is because internal energy focuses on molecular and atomic interactions, not nuclear ones.
Nuclear energy comes from the binding energy that holds protons and neutrons together in the nucleus. It can be released through nuclear reactions such as fission (splitting heavy nuclei) or fusion (combining light nuclei), processes involved in nuclear reactors and stars.
While immensely powerful, nuclear energy involves changes at the nuclear level, distinguishing it from the electronic, vibrational, and rotational energies that constitute internal energy.

Gravitational Pull

Gravitational pull refers to the force of attraction between two masses. Unlike vibrational and rotational energies, gravitational pull is an external force and does not contribute to a system's internal energy.
The energy arising from gravitational pull can affect the potential energy of a system as a whole, especially in larger systems like planets and stars. However, for typical internal energy considerations in a smaller, localized system, such as a gas in a container, gravitational effects are negligible.
Hence, in the context of internal energy, gravitational pull is considered an external energy factor. It influences the system's position in space but does not directly impact the energy contained within the molecules or atoms of the system.