Chemical energy

“ When this condition is fulfilled, energy is at once manifest. We must admit that it existed in the latent state, in the state of chemical potential energy. Under the impulse received, the carbon combines with the oxygen and forms carbonic acid, C + 2O becomes CO2; potential energy is changed into actual chemical energy, and immediately afterwards into thermal energy. We should have only a very incomplete and fragmentary view of the reality of things if we were to consider this phenomenon of combustion in isolation. ”

“ The two previous varieties of energy may be viewed as associated with molecules rather than with atoms, and with the force of cohesion rather than with that of chemical affinity. Proceeding now to atomic force, we have a species of energy of position due to the separation of different atoms under the strong chemical attraction they have for one another. Thus, when we possess coal or carbon and also oxygen in a state of separation from one another, we are in possession of a source of energy which may be called that of chemical separation. ”

“ This in turn may be changed into the energy of motion, as when the current is used for propelling the cars, or into the energy of heat and light, as when it is used for heating and lighting the cars. Again, the energy of coal may be converted into energy of heat and subsequently of motion, as when it is used as a fuel in steam engines.
Since the energy possessed by coal only becomes available when the coal is made to undergo a chemical change, it is sometimes called chemical energy. It is this form of energy in which we are especially interested in the study of chemistry. ”

“ We have, in fact, the familiar act of combustion, and, as its consequence, the chemical union of the carbon or coal with the oxygen of the air, carbonic acid being the result. Here, then, we have a very powerful force acting only at a very small distance, which we name chemical affinity, inasmuch as it represents the attraction exerted between atoms of different bodies in contradistinction to cohesion, which denotes the attraction between molecules of the same body. ”

“ The example is typical: nature and art abound with cases where a little energy, rightly directed, controls energy vastly, perhaps infinitely, greater in quantity. Often in a chemical compound the poise of attraction is so delicate that it may be disturbed by a breath, or by a note from a fiddle, as when either of these induces iodide of nitrogen to explode. A beam of light works the same result with a mixture of chlorine and hydrogen. One of the most [338] familiar facts of chemistry is that a fuel, such as coal, may remain intact in air for ages. ”

“ From the standpoint of the law of conservation of energy, the relation between chemical and thermochemical action bears the following aspect:—A given amount of any substance under given conditions possesses a perfectly definite amount of intrinsic energy, and, no matter what chemical and physical transformations the substance may undergo, it will, when it returns to its original state, possess the original amount of intrinsic energy. ”

“ Hydrogen and oxygen gases in separate receivers might remain tranquil and unchanged for ages, and it depends upon the choice of the experimenter, when he wishes to render their energy available, whether their intense chemical force shall take the form of heat or give forth an electric current. ”

“ Oxygen and nitrogen, nitrogen and hydrogen, hydrogen and carbon, which show no affinity for each other under ordinary circumstances, readily unite when one or both are in a nascent condition. The reason seems to be that, when the elements of a compound are torn asunder, the chemical affinity which previously bound them together is set free, ready and eager to unite the nascent elements with whatever they come in contact with. ”

“ Chemical affinity depends entirely upon the energy with which particles of different kinds attract each other. Oxygen and hydrogen are particles of different kinds, and it is their attraction to each other which makes them chemically combine and produce water. ”

“ The store of force or energy going to the formation of new compounds may, after several combinations, accomplished with an absorption of heat, at last diminish to such a degree that indifferent compounds will be obtained, although these sometimes, by combining with energetic elements or compounds, give more complex compounds, which may be capable of entering into chemical combination. Among elements, gold, platinum, and nitrogen have but little energy, whilst potassium, oxygen, and chlorine have a very marked degree of energy. ”

“ In coal we have the energy which plants absorbed from the sun ages ago, stored up in a potential form. The carbon atoms are ready to rush into union with oxygen atoms, and convert their energy of position into the energies developed by chemical action, viz., heat, light, &c. Energy is thus constantly shifting its form from actual to potential, and vice versâ, and exhibiting itself under the various transformations of force, as when sun-force changes to chemical action, chemical action to heat, heat to electricity, &c. ”

“ While every element present in living substance may assist in the work, the energy-traffic is carried on chiefly amongst the four elements, nitrogen, oxygen, carbon and hydrogen. Nitrogen is remarkable for the instability of its chemical compounds—the readiness with which they change their composition—and there is little doubt that on this property depends the extreme sensitiveness of living substance. Carbon and hydrogen have the property of combining together to build up complex compounds, with great storage of potential energy ”

“ A man, like a steam-engine, can not move without his appropriate fuel; and if the fuel is not supplied, the fire goes out and the man dies. The exact manner in which the materials are utilized for keeping up this vital flame is the question to which we must now address ourselves.
Food-stuffs and coal agree essentially in the chief characteristics of their chemical constitution. Both consist mainly of hydrogen and carbon, and both possess energy in virtue of the fact that their affinities for oxygen are not satisfied. Water contains hydrogen, and carbonic acid contains carbon ”

“ There is yet another consideration, and one of vital importance, to be taken into account, viz., that—whether we use the electric light derived from a dynamo-electric source, or coal-gas—our primary source of illuminating power is coal, or rather the chemical energy derivable from the combination of its hydrogen and carbon with oxygen. Now this chemical energy is a limited quantity, and the progress of Science can no more increase this quantity than it can make a ton of coal weigh 21 cwts. ”

“ Heat, as we have seen, is very frequently influential in performing this separation, and its energy is spent in so doing; but other energetic agents produce chemical decomposition as well as heat. For instance, certain rays of the sun decompose carbonic acid into carbon and oxygen in the leaves of plants, and their energy is spent in the process ”

“ An ounce of radium salt will give out enough heat in one hour to melt an ounce of ice and in the next hour will raise this water to the boiling point, and so on again and again without cessation for years, a fire without fuel, a realization of the philosopher's lamp that the alchemists sought in vain. The total energy so emitted is millions of times greater than that produced by any chemical combination such as the union of oxygen and hydrogen to form water. ”

“ The present view requires that the energy of chemical constitution shall be very great compared with the thermal energy; but for this very reason our means of chemical decomposition are limited, so that only a part of that energy is experimentally realizable. ”

“ What the chemical ether is capable of effecting in a gentle manner, so to speak, in cooperation with the inertness-overcoming power of the warmth-ether, can be imitated physically only by an extraordinary concentration of external energy and the use of masses of material substance. ”

“ It was that vital energy alone which not only built up the living tubes and cells, but which filled them with the living organic matter capable of resisting the chemical affinities of the inorganic world. But when that energy became feeble, and when at last it ceased, the once powerful structure descended again to that lower level of the inorganic, and subject to all its laws. ”

“ We know that, floating around us, these volatilized bodies exist in some material form, and numerous experiments in chemistry are calculated to convince us, that the most attenuated air is capable, with a slight change of circumstances, of being converted into the condition of solid masses. Hydrogen gas, the lightest, the most ethereal of the chemical elements, dissolves iron and zinc, arsenic, sulphur, and carbon; and from the transparent combinations thus formed, we can with facility separate those ponderous bodies. Such substances must exist in our own atmosphere ”

“ To take a simple example:—oxygen and hydrogen are two gases which may be mixed in all proportions at ordinary temperatures, and it is easy to show that the properties of the products are simply those of mixtures of the two free gases. If, however, an electric spark be passed through the mixtures, powerful chemical union ensues, with its concomitants, great evolution of heat and consequent rise of temperature, and a compound, water, is formed which presents physical and chemical properties entirely different from those of its constituents. ”

“ When oxygen combines with a single element, what is the compound called? We have found that O makes up a certain portion of the air; later, we shall see how large the proportion is. Its tendency to combine with almost everything is a reason for the decay, rust, and oxidation of so many substances, and for conflagrations, great and small. New compounds are thusformed, of which O constitutes one factor. Water, H2O, is only a chemical union of O and H. Iron rust, Fe2O3 and H2O, is composed of O, Fe, and water. The burning of wood or of coal gives rise to carbon dioxide, CO2, and water. ”

“ When we burn wood for heat, we are using energy that the tree took from the sun. When we burn coal or oil, we are using the energy of sunlight that was stored many millions of years ago.
All of this energy is stored in the atoms of the wood, coal, or oil. But when we burn these materials for fuel, we release only the energy of the electrons. ”

“ When we take a piece of coal and a lot of free oxygen, we possess energy in the dormant state. But though the oxygen has strong attractions for the carbon and hydrogen, they can not unite, because their atoms do not come into close contact with one another, and because the two last-named substances are bound up in the solid form of the coal. ”

“ If the plant is burned, the changes which took place in the formation of the compounds present are largely reversed. The carbon and hydrogen present combine with oxygen taken from the air to form carbon dioxide and water, while the energy absorbed from the sun's rays is liberated in the form of energy of heat. ”

“ It is clear that were any texture known which would permit a heat-impulse to pass through it in one direction only, nothing more would be necessary than to place a portion of gas in such a receptacle of this substance, so faced as to permit egress but not entrance of the heat, and the gas thus enclosed, were it hydrogen itself, would very soon become liquid and solid, through spontaneous giving off of its energy, without any manipulation whatever. ”

“ From these experiments, both analytical and synthetic, we may now affirm that we have ascertained, with as much certainty as is possible in physical or chemical subjects, that water is not a simple elementary substance, but is composed of two elements, oxygen and hydrogen; which elements, when existing separately, have so strong affinity for caloric, as only to subsist under the form of gas in the common temperature and pressure of our atmosphere. ”

“ There are numerous well-known cases, in which substances, such as oxygen and hydrogen, act readily in their nascent state, and produce chemical changes which they are not able to effect if once they have assumed the gaseous condition. ”

“ Charcoal and those complex non-volatile organic substances which represent the gradual transitions to charcoal [19] and form the principal [355] solid substances of organisms, contain a store or accumulation of internal power in the form of the energy binding the atoms into complex molecules. When charcoal or complex compounds of carbon burn, the energy of the carbon and oxygen is turned into heat, and this fact is taken advantage of at every turn for the generation of heat from fuel. [20]
No other two elements are capable of combining together in such variety as carbon and hydrogen. ”

“ The third of the fundamental laws of chemistry stated above (generally known as the law of Gay-Lussac) declares that, when two or more of the factors or products of a chemical process are aëriform, the volumes of these gaseous substances bear to each other a very simple ratio. Here, again, numerous experiments may be contrived to illustrate the law. Water, when decomposed by electricity, yields hydrogen and oxygen gases whose volumes bear to each other the ratio of two to one. ”

“ Just analogous is our action when we apply a match to the coal. The heat first disintegrates or disunites little atoms of the hydrocarbons which make it up, and sets them in a state of rapid vibration among themselves. This vibration brings them into contact with the atoms of oxygen, which at once unite with them, causing a fresh development of heat, and a liberation of all the dormant energy, which immediately assumes the active form. ”