Calories , 721 measuring

For fuels it is quite usual to employ kilocalories per kilogram as a measure of calorific value while for foods the unit used is kilocalories per gram. This, however, is often abbreviated to Calories , so that a value for carbohydrates of 4-1 Calories per gram is 4100 calories per gram. 

The illustrative data presented in Table VII-3 indicate that the total surface energy may amount to a few tenths of a calorie per gram for particles on the order of 1 /xm in size. When the solid interface is destroyed, as by dissolving, the surface energy appears as an extra heat of solution, and with accurate calorimetry it is possible to measure the small difference between the heat of solution of coarse and of finely crystalline material. 

Fig. 4. The effect of temperature for Mng 6 Zng 3 Fe Fe on (a) initial magnetic permeabiUty, )J., measured on a polycrystalline toroid appHed as a core for a coil driven by a low (B <0.1 mT) ampHtude, low (10 kHz) frequency sinusoidal signal and (b) magnetocrystalline anisotropy constant, measured on a monocrystalline sphere showing the anisotropy/compensation temperature Tq and the Curie temperature, T. To convert joules to calories, divide by...

Heat is measured in term.s of the calorie, defined as the amount of heat necessary to raise the temperature of 1 gram of water at a pressure of 1 atmosphere firom 15 to 16 °C. This unit is sometimes called the small calorie, or gram calorie, to distinguish it from the large calorie, or kilocalorie, equal to 1000 small calories, which is used in nutritional studies. In mechanical engineering practice in the United States and the United Kingdom, heat is measured in British thermal units (Btu). One Btu is the quantity of heat required to raise the temperature of 1 pound of water 1 ° F and is equal to 252 calories. 

Body activity also adds to the metabolic rate. In general, the more strenuous the activity, the more work is done and the greater the increase in metabolic rate. Bor an adult male of average size, the BMR (measured lying down) accounts for 1,500-1,600 Calories per day. If this subject sat still but upright in a chair, he would use over 2,000 Calories per day, and if he engaged in... 

The metabolic rate can be measured in several ways. When no external work is being performed, the metabolic rate equals the heat output of the body. This heat output can be measured by a process called direct calorimetry. In this process, the subject IS placed m an insulated chamber that is surrounded by a water jacket. Water flows through the jacket at constant input temperature. The heat from the subject s body warms the air of the chamber and is then removed by the water flowing through the jacketing. By measuring the difference between the inflow and outflow water temperatures and the volume of the water heated, it is possible to calculate the subject s heat output, and thus the metabolic rate, in calories. 

Measurements of energy are made in terms of absolute joules, but engineering practice has persistently retained the thermochemical calorie as the unit of energy. The two are related by the definition ... 

The measurement of reaction heats is called calorimetry—a name obviously related to the unit of heat, the calorie. You already have some experience in calorimetry. In Experiment 5 you measured the heat of combustion of a candle and the heat of solidification of paraffin. Then in Experiment 13 you measured the heat evolved when NaOH reacted with HC1. The device you used was a simple calorimeter. 

The zero calorie is 0 06 per cent, larger than the 15° calorie, whilst the mean calorie is 008 per cent. (Behn) — 0 2 per cent. (Dieterici) larger than the 15° calorie. All temperatures are supposed to be measured on the constant pressure hydrogen thermometer. 

Definition.—The heat absorbed in producing a change of physical state or chemical composition of a system, at constant temperature and pressure, is called the latent heat of the given transition, and is measured by the number of calories absorbed during the transition of unit mass of the substance from the initial to the final state. 

There is a fixed relation between the measure of a quantity of work and that of the quantity of heat obtained from it by complete conversion. If these- two measures are expressed in terms of the erg and the calorie respectively as units, there will also be a relation between the erg and the calorie. Heat, considered as a form of energy, may be measured in ergs, i.e., in work units, and to convert the measure of a quantity of heat expressed in calories into the measure. of the same quantity expressed in ergs, we must find the number of times the erg is contained in the calorie, and multiply this by the measure of the given quantity of heat in calories. It is a relation between units which is involved. 

Incidentally, air blast effects correlate much better with computed Q s rather than calori-metrically measured Q s (Ref 6)... 

Professor Bothwell determined from the wrapper the number of calories in a candy bar. He then burned the entire candy bar and measured the amount of heat released. His experiment was most likely designed to demonstrate —... 

The amount of heat released by the complete combustion of one mole of a substance is defined as the heat of combustion, AAVcomb The amount of heat released may be measured in calories (cal) or in joules (J). A calorie is the amount of heat needed to raise the temperature of one gram of water one degree Celsius. The SI unit of heat is the joule. One joule is equal to 4.184 calories. 

Measuring and Using Numbers Calculate the number of calories of heat absorbed by the water used in each trial. 

Frankland discovered the fundamental principle of valency—the combining power of atoms to form compounds. He gave the chemical bond its name and popularized the notation we use today for writing chemical formulas. He codiscovered helium, helped found synthetic organic and structural chemistry, and was the father of organometallic chemistry. He was also the first person to thoroughly analyze the gases from different types of coal and—dieters take note—the first to measure the calories in food. 

In the DSC method, the sample and reference are maintained at the same temperature and the heat flow required to keep the equality in temperature is measured. Hence DSC plots are obtained as the differential rate of heating (in units of watts/second, calories/second, or Joules/second) against temperature. The area under a DSC peak is directly proportional to the heat absorbed or evolved by the thermal event, and integration of these peak areas yields the heat of reaction (in units of calories/second gram or Joules/second gram). 

The diets were a measured, laboratory-controlled diet based on ordinary foods. Fats provided 30% of the dietary calories. Saturated to monounsaturated to polyunsaturated fatty acid ratios are listed below each test fat. 

Effects of two levels of dietary fat on dietary calcium utilization were investigated in another study conducted at the University of Nebraska. A group of 10 healthy, young adult subjects who were fed a measured, laboratory controlled diet based on ordinary foods providing 43% of the calories from mixed sources of fat were individually age, sex, race, and weight matched to subjects from other studies consuming measured, laboratory controlled diets providing approximately the same amount of calcium but only 23% of the calories from various fat sources. Other aspects of these studies were basically as previously described. 

Nutritional energy values are usually measured in kilocalories (kcal or simply calories). One kilocalorie represents the amount of heat required to raise the temperature of 1 kg of water by 1°C at room temperature. In the metric system, the energy value is expressed in joules (J), with 1 kcal being equal to 4.184 kilojoules (kJ). 

A summary of the electrochemical formulae developed above is provided in Table 7.3. AG, pe, E, and K contain virtually the same thermodynamic information. While is the quantity that is analytically measured, pe is preferred by marine chemists as it is temperature independent and numerically easier to work with. AG is often used to compare the relative stability of species because it provides a measure of energy yields in units of calories or joules. A comparison of the three electrochemical scales at 25°C is given in Figure 7.3. The merits of each thermodynamic parameter will become evident in the next section of the chapter where the energetics of some marine redox processes are considered. 

Calorie A measure of heat energy. One (1) calorie is the amount of heat energy required to raise 1 g of pure water 1°C from 14.5 to 15.5°C. 

Having observed a decrease in appetite and thirst when testing BZ, we decided to measured caloric and fluid intake more precisely in the EA 3443 series. At the incapacitating dose, calories ingested and fluid consumed both dropped by about 40%. Sleep duration, also measured, increased at the lower doses but seemed to drop precipitously at the incapacitating dose. This seeming insomnia, however, was illusory. Delirious subjects appeared physically awake, but were asleep in terms of brain electrical activity - the so-called pseudowakeful state. ... 

There is essentially no difference between work and energy. Both are measured in joule (J = 1 N m). An outdated unit is the calorie (1 cal = 4.187 J). Energy is defined as the ability of a system to perform work. There are many different forms of energy—e.g., mechanical, chemical, and radiation energy. 

For chemical reactions and phase transformations, the energy absorbed or liberated is measured as heat. The principal unit for reporting heat is the calorie, which is defined as the energy needed to raise the temperature of 1 gram of water at l4.5° C by a single degree. The term kilocalorie refers to 1,000 calories. Another unit of energy is the joule (rhymes with school), which is equal to 0.239 calories. Conversely, a calorie is 4.184 joules. The translation of calories to joules, or kilocalories to kilojoules, is so common in chemical calculations that you should memorize the conversion factors. 

It is apparent from the foregoing that the B.E.T. method will give values for the monolayer which are too large when applied to clean metal surfaces using a gas whose heat of adsorption is large relative to that in ordinary van der Waal s adsorption. With a heat of adsorption of 10,000 calories on iron, nitrogen is unsuitable for surface measurements of such metals by the B.E.T. method when absolute best values are of interest. 

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