Internal Energy of an Atom: Heat as Change of Internal Energy

Emmanuel J. Chamorro Rivera

Energy, the ability to do work, and the concept that keeps every particle in the universe moving, reacting; for us this concept is difficult to understand, but it can be calculated. Kinetic energy and potential energy are two basic types of energy that are particular to the system, but those two are derivatives of an even greater energy, the contact between electrons of an atom. In other words when we touch something, the electrons of the tip of our fingers have contact with the electrons of the object. That is precisely the source of sounds and transference of heat. If that is the case, then the atoms carry an internal energy which makes possible for them to do work, and exert forces to different directions. This means that this energy can be transferred and used, but even more important this energy can describe the elements and the components in matter.

The only thing that is missing is an equation, only a formula to calculate this energy; but it is not simple as it sounds. To find it, speed, acceleration, and position have to be known, which to find for an atom is extremely hard to find. Also Heisenberg’s uncertainty principle can explains that finding those for an electron is impossible at the same time, so the choice of using electrons to measure it also becomes complicated. Although there is another approach, for example, water vapor in a sealed refrigerator.  We know that water then would eventually turn to liquid, or solid, so if viewed from a chemical point we know that the water vapor is releasing energy, which can be measured. Now must we ask what type of energy is it liberating. Is it only thermal? Well, yes, it is thermal, but also it can be seemed as internal energy. The state is a property of matter which atoms move a different speed. So the thermal energy can be seemed like a conversion from internal energy to thermal energy. Which thermodynamics help to resolve these problems as seen in:

∆E_int=Q=mC_s ∆T ,for changes of temperature in same phase

∆E_int=Q=n∆H,for changes of phases

m=mass

C_s=constant of specific heat

T=temperature

n=moles

H=entalpy associated to the change of phase

But what exactly does internal energy implies, well we can use the knowledge of chemistry to define the term of internal energy. Now let’s remember heating curves, when a compound is solid, it needs to absorb internal energy in order to change phases. Well this may mean that compounds that are gas at room temperature have more internal energy than an abject which is solid at room temperature. For example, we have one gram of ice in a closed system, if we heat it up and have the same amount of water vapor in the same closed system; the vapor exerts more force in terms of pressure than the solid. Ergo the internal energy is larger when a compound is in gaseous state.  Now what may this imply? In chemistry there is a term to describe why does certain elements are in different phases, known as intermolecular forces. The larger the forces, stronger are the bonds between the atoms; the more likely the compound would be solid at certain temperature. Well this can give us a proportion to internal energy:

E_int∝(1/F_(inter ) ),F_inter=intermolecular forces

This proportion may seem easy at first, but the term of intermolecular forces is not yet defined as a number; it is defined as a theoretical term. Finding that number is the key to finding the internal energy of a compound in any time in a specific temperature, and from this then the composition can be known. To find the value of the forces, as well as the dimension, experiments have to be conducted for further analysis.

Internal energy is the fundamental energy of all particles, how it changes can be calculated, but the exact value is a mystery. Atoms contain this energy which allows them to make work. This energy is a property of matter itself. The understanding of this energy may drive us to understand more about atoms and how they react. Needless to say this energy is present at all times of our daily lives. Measuring it like another type of energy should be possible, even if now it seems improbable to do so.  The proportions are theoretically easy to find, but the true values are far from being, found. With the adequate equipment and extensive knowledge of composition of matter, eventually should lead to the value of intermolecular forces, which is key to understanding the energy which exist in every atom in the universe: internal energy.