Chemical property The ability of a substance

Chapters 1 through 3 present the basic mathematics and the language of chemistiy, including an explanation of the metric system and significant figures. In Chapter 4 we present chemical properties—the ability of a substance to form new substances. Then, in Chapter 5, students encounter the history and language of basic atomic theory. 

Chemistry is concerned with the properties of matter, its distinguishing characteristics. A physical property of a substance is a characteristic that we can observe or measure without changing the identity of the substance. For example, a physical property of a sample of water is its mass another is its temperature. Physical properties include characteristics such as melting point (the temperature at which a solid turns into a liquid), hardness, color, state of matter (solid, liquid, or gas), and density. A chemical property refers to the ability of a substance to change into another substance. For example, a chemical property of the gas hydrogen is that it reacts with (burns in) oxygen to produce water a chemical property of the metal zinc is that it reacts with acids to produce hydrogen gas. The rest of the book is concerned primarily with chemical properties here we shall review some important physical properties. 

If the combination of a high-resolution separation system with a physicochemical detection principle is specific to properties of many harmful (toxic) chemicals, then a straightforward approach may be possible (27). Electron capture detection (ECD) registers electronegative compounds. Since the early 1960s, Lovelock (28) has pointed at the possible link between the ability of a substance to capture electrons and its biological action. 

Chemical property A type of property that characterizes the ability of a substance to change into a different substance. 

Polymorphism refers to the ability of a substance to exist in more than one crystalline structure, which has different arrangements in space (i.e., different cell dimensions and cell packing) of the same structural unit(s) (i.e., same chemical composition). Polymorphs can display widely different physical and chemical properties, including melting point, spectroscopic behavior, solubility, density, hardness, crystal shape, physical and chemical stability, and dissolution-time profile. 

Physical properties alone are not enough to describe a substance. For a complete description, you need to know about another set of properties called chemical properties. Chemical properties are those that can be observed only when there is a change in the composition of the substance. Chemical properties describe the ability of a substance to react with other substances or to decompose. A chemical property of iron, for example, is that it rusts at room temperature. Rusting is a chemical reaction in which iron combines with oxygen to form a new substance, iron oxide. Aluminum reacts with oxygen too, but the compound formed, aluminum oxide, coats the aluminum and protects it from further oxidation. Platinum does not react with oxygen at room temperature. Lack of reactivity is also a chemical property. 

It is now evident that the ideal two-dimensional gas equation of state, eq. (11.16), can be applied to dilute adsorption layers of both soluble and insoluble surfactants. At the same time, the similar behavior of surfactants in the dilute adsorption layers, regardless of the nature of the constituent molecules and their interactions with the solution underneath the adsorption layer, leads to the conclusion that the relationship between the adsorption and the two-dimensional pressure, 7r(T), is the principal characteristic of the adsorption layer, independent of the bulk properties of the surfactant solution. Conversely, the dT/dc value, characterizing the ability of a substance to adsorb, significantly depends on the nature of both the surfactant and the solvent. This value increases sharply as we move from one member of a homologous series to the other. Different abilities of surfactants to adsorb, on the one hand, and the identity of their behavior in the dilute adsorption layer itself, on the other hand, indicate that the increase in the dT/dc value in the homologous series is related to the differences in behavior of the members of homologous series in the solution and not in the adsorption layer. The latter indicates that for dilute adsorption layers the q0 - q(0s) value is determined by the state of energy of surfactant molecules in the bulk. In the other words, the standard part of the chemical potential of molecules in the adsorption layer, qj,s), (eq. (II. 14)) can be considered to be constant at low adsorption, and thus... 

Some properties of a substance are not obvious unless the substance has changed composition as a result of its contact with other substances or the application of thermal or electric energy. The ability of a substance to combine with or change into one or more other substances is called a chemical property. 

How do we recognize substances Each substance has a set of properties that are characteristic of that substance and give it a unique identity. Properties— the personality traits of substances—are classified as either physical or chemical. Physical properties are the inherent characteristics of a substance that can be determined without altering its composition they are associated with its physical existence. Common physical properties include color, taste, odor, state of matter (solid, liquid, or gas), density, melting point, and boiling point (see Figure 4.1). Chemical properties describe the ability of a substance to form new substances, either by reaction with other substances or by decomposition. 

Chemical properties describe the ability of a substance to interact with other substances to form different substances. 

There is clearly a conceptual relationship between the properties called nucleophilicity and basicity. Both describe a process involving formation of a new bond to an electrophile by donation of an electron pair. The pKa values in Table 5.5 refer to basicity toward a proton. There are many reactions in which a given chemical species might act either as a nucleophile or as a base. Scheme 5.4 lists some examples. It is therefore of great interest to be able to predict which chemical species Y " will act as nucleophiles and which will act as bases under a given set of circumstances. The definition of basicity is based on the ability of a substance to remove protons and refers to an equilibrium. 

The physical properties of the material depend on the phase of the material. When undergoing a phase change, the substance remains chemically identical, but its appearance (the way it appears to the naked eye) is different. The physical state, size, or shape may have changed but there is no creation of a new substance in a physical change. The identity of the substance is preserved. Important physical properties in engineering and chemistry include density, thermal conductivity (the ability of a substance to transfer heat energy), and specific heat (the ability of the substance to retain energy). 

A change of state is a physical change that does not alter chemical properties. It usually takes place by increasing or decreasing the temperature of a substance. The ability to change the state of substances is important in the synthesis and purification of chemicals. 

The ability of a material to resist chemical attack (the attack is dependent on the method of test and its severity and is measured by determining the changes in physical properties [ASTM, 1982]. Reaction of a substance with oxygen with release of heat, generally accompanied by flaming and/or emission of smoke. Any chemical process that produces light and heat, either as glow or flame. 

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