The Chemical Properties of Substances

The chemical properties of a substance are those properties that relate to its participation in chemical reactions. 

Chemical reactions are the processes that convert substances into other substances. 

Thus sodium chloride has the property of changing into a soft metal, sodium, and a greenish-yellow gas, chlorine, when it is decomposed by passage of an electric current through it. It also has the property, when it is dissolved in water, of producing a white precipitate when a solution of silver nitrate is added to it and it has many other chemical properties. 

Iron has the property of combining readily with the oxygen in moist air, to form iron rust whereas an alloy of iron with chromium and nickel (stainless steel) is found to resist this process of rusting. It is evident from this example that the chemical properties of materials are important in engineering. 

Most substances have the power to enter into many chemical reactions. The study of these reactions constitutes a large part of the study of chemistry. Chemistry may be defined as the science of substances —their structure, their properties, and the reactions that change them into other substances. 

---

Now that we have considered some of the ways in which the idea of resonance has brought clarity and unity into modem structural chemistry, has led to the solution of many problems of valence theory, and has assisted in the correlation of the chemical properties of substances with the information obtained about the structure of their molecules by physical methods, we may well inquire again into the nature of the phenomenon of resonance.1... 

The Chemical Inherent Safety Index deals with the hazards which are related to the chemical properties of substances in the process. The Index has been divided into subindices for reaction hazards and hazardous substances. 

The chemical properties of substances allow them to transform to new substances. Both natural gas and baking soda transform to carbon dioxide and water. Copper transforms to patina. 

Because it is generally accepted that resonance influences the chemical properties of substances in which it occurs, consideration of the comparative stability of the free radicals, in terms of theory of resonance (P, 10), provides substantiation of the compounds relative efficiencies as antiozonants. 

The thermodynamic and physical properties of pure steam are well estabUshed over the range of pressures and temperatures used. The chemical properties of steam and of substances ia steam, their molecular stmctures, and iateractions with the soHd surfaces of containments need to be more fliUy explored. 

Paiistcnbach luas provided lui excellent review of the physical and chemical properties of substances uid how tliis information is used to predict tlie... 

But what would become of Mendeleev s periodic system which now seemed to consist of 300 or so "elements" To some chemists, the discovery of isotopes implied the end of the periodic system as it was known.3 These chemists suggested that it would be necessary to consider the individual new isotopes as the new "elements." But the chemist Paneth adopted a less reductionist approach, arguing that the periodic table of the familiar chemical elements should be retained because it dealt with the "elements" that were of interest to chemists. A justification for this view was provided by the fact that, with a few exceptions, the chemical properties of isotopes of the same element are indistinguishable.4 Moreover, Paneth appealed to Mendeleev s distinction between the two senses of the concept of an "element" in order to provide a philosophical rationale for the retention of the chemist s periodic table. Paneth argued that the discovery of isotopes of the elements represents the discovery of new elements as simple substances, whereas periodic... 

The chemical properties of this hypothetical benzene would be just those expected for the valence-bond structures I and II, and, indeed, the substance would be correctly described as a mixture of these two isomers or tautomers. 

We wish to thank Professor F. W. Bergstrom for the sample of pyrazine, Dr. W. E. Vaughan for that of tetrabromobutane, Dr. K. J. Palmer for his help with experimental work, Dr. Sidney Weinbaum for assistance in the preparation of the figures, and Dr. E. R. Buchman for discussion of the chemical properties of the substances. We are especially indebted to Professor L. O. 

Apart from the three broad categories of student conceptions discussed above, students displayed several inappropriate conceptions relating to the stractural properties of substances. For example, 14% of students suggested that Mg + ions were present in magnesium ribbon. A second example involved the chemical reaction between copper(II) oxide powder and dilute sulphuric acid. In this instance, 25% of students suggested that Cu + ions were present only in aqueous solution but not in the solid and liquid states. This view was rather unexpected because students had earlier been introdnced to ionic and covalent compounds. It is likely that students had merely rote-learned the general rale without sufficient understanding that ionic solids are formed between metallic and non-metallic elements. 

The physical properties of substances do not involve chemical changes. Color (see Textbox 17) and crystal structure (see Textbox 21), for example, are physical properties that are characteristic of a substance that serve to identify most substances. Other physical properties, such as density, hardness (see Table 3), refractive index (see Table 19), and heat capacity (see Table 101), are also useful for characterizing and identifying substances as well as distinguishing between different substances. 

Chemical Effects of Temperature. Changes in temperature also affect the chemical properties of materials. The rate at which most chemical reactions take place, for example, is roughly doubled when the temperature of the reactants increases by 10°C. Consequently, any increase in temperature intensifies the rate at which most materials react with substances in the environment such as oxygen, water, and atmospheric and soil pollutants, and hastens their chemical degradation. 

What was the distinction between quantum chemistry and chemical physics After the Journal of Chemical Physics was established, it was easy to say that chemical physics was anything found in the new journal. This included molecular spectroscopy and molecular structures, the quantum mechanical treatment of electronic structure of molecules and crystals and the problem of chemical binding, the kinetics of chemical reactions from the standpoint of basic physical principles, the thermodynamic properties of substances and calculation by statistical mechanical methods, the structure of crystals, and surface phenomena. 

In this section, you have used Lewis structures to represent bonding in ionic and covalent compounds, and have applied the quantum mechanical theory of the atom to enhance your understanding of bonding. All chemical bonds—whether their predominant character is ionic, covalent, or between the two—result from the atomic structure and properties of the bonding atoms. In the next section, you will learn how the positions of atoms in a compound, and the arrangement of the bonding and lone pairs of electrons, produce molecules with characteristic shapes. These shapes, and the forces that arise from them, are intimately linked to the physical properties of substances, as you will see in the final section of the chapter. 

To understand the overall biological activity of quinoid compounds, it is necessary to study the chemical properties of these substances. Inasmuch as the cellular damage that is induced by quinones resembles that seen after radiolysis, the most prominent reactions involving quinones are probably DNA damage and generation of oxygen free radicals. 

Chemical reactions take place when the reacting atoms, molecules or ions collide with each other. Therefore the outer electrons are Involved when different substances react together and we need to understand the electronic structure of atoms to explain the chemical properties of the elements. Much of the information about the electronic structure of atoms and molecules is obtained using spectroscopic techniques based on different types of electromagnetic radiation. 

Be properly dressed e.g., safety eyeglasses, long pants, labcoat, closed-toe shoes, gloves (these must be appropriate for the chemical properties of radiolabeled substances), lead apron (if recommended), and wrist guards. Dosimeters must be worn in recommended locations (wrist, finger, lapel, etc.). 

Little has yet been reported on the chemical properties of blood group B and 0 substances Table III (page 46) summarizes the information thus far obtained. 

---