Irreversible chemical and physical

Coatings that are exposed to weathering undergo aging. Aging is defined as the sum of all irreversible chemical and physical processes that occur in the coating over the course of time. Aging is mainly caused by radiation, temperature, and moisture (rain and atmospheric humidity). 

A thermosetting synthetic resin is one that undergoes an irreversible chemical and physical change during curing to become substantially infusible and insoluble. The term thermosetting is applied to the resin both... 

We have introduced the concept of dissipation in Chap. 2.3 it is related to the entropy production in irreversible chemical and physical systems, and has been discussed in the scientific literature and in texts extensively. Here we present some relatively new developments and return to the issue of dissipation and efficiency in chemical reactions in Chap. 13 and later. 

Chemical "affinity" remained part of the tool kit of the chemist, however badly defined and understood. Affinity cannot simply be explained away as heat, insisted Wurtz, a leading advocate of chemical and physical atomism in France in the generation following Dumas.58 As we will see in chapter 5, "energy" replaced "affinity" in the late 1800s as the driving force of chemical reactions. In addition, the concepts of spontaneity and irreversibility entered the domain of physics, undermining the classical mechanics of matter and force in which processes are, in principle, reversible. Conceptually, the notions of spontaneity and irreversibility were more closely allied with experimental results in classical chemistry than in classical physics. 

The adsorption process can be described as molecules leaving a solution and being held on the solid surface by chemical and physical bonding. If the bonds that form between the adsorbate and adsorbent are very strong, the process is almost always irreversible [97-99], and chemical adsorption (i.e., chemisorption) is said to have occurred. On the other hand, if the bonds that are formed... 

There are precautions that must be taken when attempting to separate heavy feedstocks or polar feedstocks into constituent fractions. The disadvantages in using ill-defined adsorbents are that adsorbent performance differs with the same feed and in certain instances may even cause chemical and physical modification of the feed constituents. The use of a chemical reactant such as sulfuric acid should only be advocated with caution since feeds react differently and may even cause irreversible chemical changes and/or emulsion formation. These advantages may be of little consequence when it is not, for various reasons, the intention to recover the various product fractions in toto or in the original state, but in terms of the compositional evaluation of different feedstocks, the disadvantages are very real. 

Quantitative and qualitative changes in chemisorption of the reactants in methanol synthesis occur as a consequence of the chemical and physical interactions of the components of the copper-zinc oxide binary catalysts. Parris and Klier (43) have found that irreversible chemisorption of carbon monoxide is induced in the copper-zinc oxide catalysts, while pure copper chemisorbs CO only reversibly and pure zinc oxide does not chemisorb this gas at all at ambient temperature. The CO chemisorption isotherms are shown in Fig. 12, and the variations of total CO adsorption at saturation and its irreversible portion with the Cu/ZnO ratio are displayed in Fig. 13. The irreversible portion was defined as one which could not be removed by 10 min pumping at 10"6 Torr at room temperature. The weakly adsorbed CO, given by the difference between the total and irreversible CO adsorption, correlated linearly with the amount of irreversibly chemisorbed oxygen, as demonstrated in Fig. 14. The most straightforward interpretation of this correlation is that both irreversible oxygen and reversible CO adsorb on the copper metal surface. The stoichiometry is approximately C0 0 = 1 2, a ratio obtained for pure copper, over the whole compositional range of the... 

The chemical and physical characteristics of phenolic resins and adhesives made from them suggest that formaldehyde emissions should be very minor ( 1 ). One reason for predicting low emissions is that very little residual free formaldehyde is present in prepared phenolic resins. This low free formaldehyde content is due to both the use of low formaldehyde to phenol mole ratios in resin preparation and to the tendency of nearly all the formaldehyde to react irreversably with the phenol. 

Catalytic deactivation may occur for a number of reasons, both chemical and physical in nature. Several authors have reported that chemical poisoning of the noble metal catalysts is the primary mechanism for phosphorus compounds. Nevertheless, inhibition also takes place. The difference between phosphorus inhibitors and poisons is that inhibitors absorb weakly on the surface and the process is often reversible. On the other hand poisoning is the irreversible loss of activity due to the strong chemisorption of the impurities in the feed on the catalytic active sites. 

The process of sterilisation is required for any product used in a situation where there is a risk of infection. Sterilisation requires the application of a chemical (biocide) to a product, or the physical removal of micro-organisms from the product. The objective is to kill the bacteria, the definition of bacterial death being the irreversible loss of reproductive ability. There are a number of chemical and physical methods available to achieve this objective. The physical methods... 

ATP is the universal energy carrier for life. It is ATP that stores energy to be used on demand, and this energy can actually take both chemical and physical forms (Pollack, 2001). The close proximity of its three phosphate complexes results in a high concentration of negative charge. Because of this, it has a high affinity for protein surfaces ATP association for the protein myosin, for instance, is practically irreversible. 

It can be proved that a system does maximum work when it is working reversibly. Real processes are irreversible, therefore there is always a loss of available energy due to chemical and physical irreversibihties. 

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