Caloric

There is one version of the caloric theory that was introduced by Antoine Lavoisier. Prior to Lavoisier's caloric theory, published references concerning heat and its existence, outside of being an agent for chemical reactions, were sparse only having been offered by Joseph Black in Rozier's Journal (1772) citing the melting temperature of ice.[2] In response to Black, Lavoisier's private manuscripts revealed that he had encountered the same phenomena of a fixed melting point for ice and mentioned that he had already formulated an explanation which he had not published as of yet.[3] Lavoisier developed the explanation of combustion in terms of oxygen in the 1770s. In his paper "Rflexions sur le phlogistique" (1783), Lavoisier argued that phlogiston theory was inconsistent with his experimental results, and proposed a 'subtle fluid' called caloric as the substance of heat.[4] According to this theory, the quantity of this substance is constant throughout the universe,[citation needed] and it flows from warmer to colder bodies. Indeed, Lavoisier was one of the first to use a calorimeter to measure the heat released during chemical reaction. Lavoisier presented the idea that caloric was a subtle fluid, obeying the common laws of matter, but attenuated to such a degree that it is capable of passing through dense matter without restraint; caloric's own material nature is evident when it is in abundance such as in the case of an explosion.[2]

Since heat was a material substance in caloric theory, and therefore could neither be created nor destroyed, conservation of heat was a central assumption.[5] Heat conduction was believed to have occurred as a result of the affinity between caloric and matter thus the less caloric a substance possessed, thereby being colder, attracted excess caloric from nearby atoms until a caloric, and temperature, equilibrium was reached.[6]

Caloric

Download 🔥 https://urlca.com/2y3Bh3 🔥

Chemists of the time believed in the self-repulsion of heat particles as a fundamental force thereby making the great fluid elasticity of caloric, which does not create a repulsive force, an anomalous property which Lavoisier could not explain to his detractors.[7]

Radiation of heat was explained by Lavoisier to be concerned with the condition of the surface of a physical body rather than the material of which it was composed.[6][8] Lavoisier described a poor radiator to be a substance with a polished or smooth surface as it possessed its molecules lying in a plane closely bound together thus creating a surface layer of caloric which insulated the release of the rest within.[6] He described a great radiator to be a substance with a rough surface as only a small amount of molecules held caloric in within a given plane allowing for greater escape from within.[6] Count Rumford would later cite this explanation of caloric movement as insufficient to explain the radiation of cold becoming a point of contention for the theory as a whole.[6]

The introduction of the caloric theory was influenced by the experiments of Joseph Black related to the thermal properties of materials. Besides the caloric theory, another theory existed in the late eighteenth century that could explain the phenomenon of heat: the kinetic theory. The two theories were considered to be equivalent at the time, but kinetic theory was the more modern one, as it used a few ideas from atomic theory and could explain both combustion and calorimetry. Caloric theory's inability to explain evaporation and sublimation further led to the rise of kinetic theory through the work of Count Rumford. Count Rumford observed solid mercury's tendency to melt under atmospheric conditions and thus proposed that the intensity of heat itself must stem from particle motion for such an event to occur where great heat was not expected to be.[3]

Quite a number of successful explanations can be, and were, made from these hypotheses alone. We can explain the cooling of a cup of tea in room temperature: caloric is self-repelling, and thus slowly flows from regions dense in caloric (the hot water) to regions less dense in caloric (the cooler air in the room).

We can explain the expansion of air under heat: caloric is absorbed into the air, which increases its volume. If we say a little more about what happens to caloric during this absorption phenomenon, we can explain the radiation of heat, the state changes of matter under various temperatures, and deduce nearly all of the gas laws.

Sadi Carnot, who reasoned purely on the basis of the caloric theory, developed his principle of the Carnot cycle, which still forms the basis of heat engine theory. Carnot's analysis of energy flow in steam engines (1824) marks the beginning of ideas which led thirty years later to the recognition of the second law of thermodynamics.

Caloric was believed to be capable of entering chemical reactions as a substituent inciting corresponding changes in the matter states of other substances.[2] Lavoisier explained that the caloric quantity of a substance, and by extent the fluid elasticity of caloric, directly determined the state of the substance.[9] Thus, changes in state were a central aspect of a chemical process and essential for a reaction where the substituents undergo changes in temperature.[9] Changes of state had gone virtually ignored by previous chemists making the caloric theory the inception point for this class of phenomena as a subject of interest under scientific inquiry.[2]

In 1798, Count Rumford published An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction, a report on his investigation of the heat produced while manufacturing cannons. He had found that boring a cannon repeatedly does not result in a loss of its ability to produce heat, and therefore no loss of caloric. This suggested that caloric could not be a conserved "substance", though the experimental uncertainties in his experiment were widely debated.

His results were not seen as a "threat" to caloric theory at the time, as this theory was considered to be equivalent to the alternative kinetic theory.[11] In fact, to some of his contemporaries, the results added to the understanding of caloric theory.

In later combination with the law of energy conservation, the caloric theory still provides a valuable analogy for some aspects of heat, for example, the emergence of Laplace's equation and Poisson's equation in the problems of spatial distribution of heat and temperature.[citation needed]

Study objectives: To assess the consistency of caloric intake with American College of Chest Physicians (ACCP) recommendations for critically ill patients and to evaluate the relationship of caloric intake with clinical outcomes.

Measurements and results: On ICU admission, severity of illness (ie, simplified acute physiology score II) and markers of nutritional status (ie, serum albumin level and body mass index) were recorded. The route of feeding (ie, enteral or parenteral), actual caloric intake (ie, percentage of ACCP recommendations: 0 to 32% [tertile I]; 33 to 65% [tertile II]; >/==" BORDER="0"> 66% [tertile III]), and evidence of GI intolerance (ie, gastric aspirate levels, >/==" BORDER="0"> 100 mL) were recorded daily. The following outcomes were assessed: status on hospital discharge (alive vs dead); spontaneous ventilation before ICU discharge (yes vs no); and ICU discharge without developing nosocomial sepsis (yes vs no). The average caloric intake among 187 participants was 50.6% of the ACCP targets and was similar in both hospitals. Caloric intake was inversely related to the mean number of gastric aspirates >/==" BORDER="0"> 100 mL/d (Spearman rho = -0.04; p = 0.06), but not to severity of illness, nutritional status, or route of feeding. After accounting for the number of gastric aspirates >/==" BORDER="0"> 100 mL, severity of illness, nutritional status, and route of feeding, tertile II of caloric intake (vs tertile I) was associated with a significantly greater likelihood of achieving spontaneous ventilation prior to ICU discharge. Tertile III of caloric intake (vs tertile I) was associated with a significantly lower likelihood of both hospital discharge alive and spontaneous ventilation prior to ICU discharge.

Conclusions: Study participants were underfed relative to ACCP targets. These targets, however, may overestimate needs, since moderate caloric intake (ie, 33 to 65% of ACCP targets; approximately 9 to 18 kcal/kg per day) was associated with better outcomes than higher levels of caloric intake.

Patients and methods: We analyzed 24-hour dietary recalls from children and adolescents (aged 2-19) in 2 nationally representative population surveys: National Health and Nutrition Examination Survey III (1988-1994, N = 9882) and National Health and Nutrition Examination Survey 1999-2004 (N = 10 962). We estimated trends in caloric contribution, type, and location of sugar-sweetened beverages and 100% fruit juice consumed.

Results: Per-capita daily caloric contribution from sugar-sweetened beverages and 100% fruit juice increased from 242 kcal/day (1 kcal = 4.2 kJ) in 1988-1994 to 270 kcal/day in 1999-2004; sugar-sweetened beverage intake increased from 204 to 224 kcal/day and 100% fruit juice increased from 38 to 48 kcal/day. The largest increases occurred among children aged 6 to 11 years ( approximately 20% increase). There was no change in per-capita consumption among white adolescents but significant increases among black and Mexican American youths. On average, respondents aged 2 to 5, 6 to 11, and 12 to 19 years who had sugar-sweetened beverages on the surveyed day in 1999-2004 consumed 176, 229, and 356 kcal/day, respectively. Soda contributed approximately 67% of all sugar-sweetened beverage calories among the adolescents, whereas fruit drinks provided more than half of the sugar-sweetened beverage calories consumed by preschool-aged children. Fruit juice drinkers consumed, on average, 148 (ages 2-5), 136 (ages 6-11), and 184 (ages 12-19) kcal/day. On a typical weekday, 55% to 70% of all sugar-sweetened beverage calories were consumed in the home environment, and 7% to 15% occurred in schools. 2351a5e196