How is Change in Internal Energy Related to Heat and Work

We get energy in various forms, including kinetic and potential energies of various types. When a system moves, we refer to it as having kinetic energy. However, even if we pin the system down and don’t allow it to move as a whole, kinetic energy is still present due to the random mobility of the system’s atoms. Furthermore, these atoms may exert forces on one another, implying that potential internal energies are connected with these “bonds.” There are no bonds in a perfect gas.

The combined total of the internal kinetic energies and the attenuated total potential energies due to atom bonding is defined as internal energy in thermodynamics.

Internal energy isn’t a brand-new notion but heat is a relatively new term in thermodynamics. Heat is a form of energy transfer. Heating occurs when two objects with different temperatures exchange energy because of the temperature difference.

In the mid-nineteenth century, the renowned Joule (mechanical equivalent of heat) experiment developed the mechanistic concept of heat. Before Joule, people thought of heat as an invisible, frictionless liquid that moved between two varying temperatures. The fluid was referred to as caloric. Hence this was dubbed the caloric model of heat.

Heat

Heat and temperature are sometimes used interchangeably, although this is incorrect. Consider sending the same quantity of heat energy to two different bodies. The temperature change will most significantly vary even if the bodies are made of the same composition (but vary in their sizes). The material’s heat capacity (C) is the source of this temperature differential. Heat capacity is a measure of a material’s ability to conserve heat without modifying the existing temperature; in other words, a substance with a low heat capacity (low C value) will experience a sharper increase in temperature when a fixed amount of heat is applied, compared to a substance with a high heat capacity (large C value).

Heat capacity trends have an interesting relationship with conductivity trends: materials with high heat capacity are often good electrical insulators, whereas those with low heat capacity are good electrical conductors. 

Two elements influence heat capacity. C grows as the mass (m) of the material present increases. The interior makeup of matter—its intermolecular forces (which define its phase) and intramolecular forces—is also a factor in its heat capacity (defining its bonding). These intrinsic contributions, which are intense or independent of the amount of matter present, are referred to as the substance’s specific heat (S.H.). The amount of energy required to elevate one gramme of material one degree in temperature is specific heat. Depending on the application, S.H. is presented in one of two preferred energy units.

These things are later transformed into molar specific heats by multiplying by the material’s molar mass, for example, in the case of liquid water.

Energy and Temperature

The temperature of matter is linked to internal energy. However, the two are not the same. The total energy of all the particles in an object or material is internal energy in thermodynamics. This contains the particles’ kinetic energy and the chemical potential energy of the bonds that connect them.

Temperature is used to determine the average particle speed. This is calculated using the kinetic energy of individual particles. When water is heated, the water molecules gain kinetic energy and accelerate. Raising the temperature of a large amount of water requires more energy since more molecules must have their speeds modified.

Example

Consider a teaspoon of boiling water heated to 100 degrees Celsius (°C) and a huge bowl of room-temperature water:

• Even though the particles have a lot of kinetic energy, there aren’t enough of them to melt an ice cube with a teaspoon of boiling water.

• An ice cube might be dissolved in a cup of room temperature water because, while each molecule has less kinetic energy, there are a lot more of them, resulting in a lot more total available power.

Conclusion

The internal energy in thermodynamics is the energy necessary to set a thermodynamic system in any given condition. The energy gained or lost due to changes in internal particle motion is used to calculate a system’s internal energy. Internal energy is a property or state function in thermodynamics that defines the energy of a substance in the absence of capillary effects and external electric, magnetic, and other fields. The value of the energy, like any other state function, is determined by the state of the material rather than the nature of the activities that led to that condition.