Examples of Internal Energy

The internal energyAccording to the First Principle of Thermodynamics, it is understood as that linked to the random movement of particles within a system. For example: batteries, stir a liquid, water vapor. It differs from the ordered energy of macroscopic systems, associated with moving objects, in that it refers to the energy contained by objects on a microscopic and molecular scale.

A) Yes, an object may be in complete rest and lack apparent energy (nor potential, neither kinetics), and yet be abuzz with molecules in motion, moving at high speeds per second. In fact, these molecules will be attracting and repelling each other depending on their conditions. chemical and microscopic factors, even though there is no movement to the naked eye observable.

Internal energy is considered a extensive magnitude, that is, related to the amount of matter in a given particle system. For it comprises all other forms of electrical, kinetic, chemical and potential energy contained in the atoms of a substance determined.

This type of energy is usually represented by the sign U.

Internal energy variation

The internal energy of the particle systems may vary, regardless of its spatial position or acquired shape (in the case of liquids Y gases). For example, when entering hot To a closed system of particles, thermal energy is added that will affect the internal energy of the whole.

However, internal energy is astatus function, that is to say, it does not attend to the variation that connects two states of matter, but to the initial and final state of it. That is why the calculation of the variation of the internal energy in a given cycle will always be zero, since the initial and final states are one and the same.

The formulations to calculate this variation are:

All these cases and others can be summarized in an equation that describes the Principle of Conservation of Energy in the system:

ΔU = Q + W

Examples of internal energy

1. Batteries. In the body of the charged batteries a usable internal energy is housed, thanks to the chemical reactions between the acids and the metals heavy inside. Said internal energy will be greater when its electrical charge is complete and less when it has been consumed, although in In the case of rechargeable batteries, this energy can be increased again by introducing electricity from the electrical outlets.
2. Compressed gases. Considering that gases tend to occupy the total volume of the container in which they are contained, since their Internal energy will vary as this amount of space is greater and will increase when it is less. Thus, a gas dispersed in a room has less internal energy than if we compress it in a cylinder, since its particles will be forced to interact more closely.
3. Increase the temperature of matter. If we increase the temperature of, for example, one gram of water and one gram of copper, both at a base temperature of 0 ° C, we will notice that despite being the same amount of matter, ice will require a greater amount of total energy to reach temperature desired. This is because its specific heat is higher, that is, its particles are less receptive to the energy introduced than those of copper, adding heat much more slowly to its internal energy.
4. Shake a liquid. When we dissolve sugar or salt in water, or we promote mixtures similar, we usually shake the liquid with an instrument to promote a greater dissolution. This is due to the increase in the internal energy of the system produced by the introduction of that amount of work (W) provided by our action, which allows greater chemical reactivity between the particles involved.
5. Steamof water. Once the water is boiled, we will notice that the steam has a higher internal energy than the liquid water in the container. This is because, despite being the same molecules (the compound has not changed), to induce transformation physics we have added a certain amount of caloric energy (Q) to the water, inducing a greater agitation of its particles.

Other types of energy

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