Calorie kilocalorie

The basic unit of energy used in accelerator physics is the electron volt (eV), which is the energy acquired by an electron when accelerated through a potential difference of one volt. An electron volt is a very small unit compared to an energy unit such as a food calorie (kilocalorie). A kilocalorie is about 26 billion trillion times as large as an eV. Common multiples of eV arc McV (niillion cV), GcV (billion cV), and TcV (trillion eV). 

The ABC cereal company is developing a new type of breakfast cereal to compete with a rival product that they call Brand X. You are asked to compare the energy content of the two cereals to see if the new ABC product is lower in calories so you burn 1.00-g samples of the cereals in oxygen in a calorimeter with a heat capacity of 600. J-(°C). When the Brand X cereal sample burned, the temperature rose from 300.2 K to 309.0 K. When the ABC cereal sample burned, the temperature rose from 299.0 K to 307.5 K. (a) What is the heat output of each sample (b) One serving of each cereal is 30.0 g. How would you label the packages of the two cereals to indicate the fuel value per 30.0-g serving in joules in nutritional Calories (kilocalories) ... 

Energy and power values for biological systems are often expressed in several different sets of units. Among these are watts, calories, kilocalories, British Thermal Units (BTU), ergs, horsepower, electron-volts, and others. Unless the same units are used on both sides of the equation, and... 

Convert the following numbers of calories/kilocalories into joules (J). 

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 SI Systeme International d Unites) unit of energy is the joule (J) An older unit is the calorie (cal) Most or game chemists still express energy changes in units of kilocalories per mole (1 kcal/mol = 4 184 kJ/mol)... 

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. 

NOTE Prices hove been converted into Btus assuming 5,800,000 Btus per barrel of oil, 3,412,000 Btus per 1000 kWh, 1,000,000 Btus per 1000 mcf of natural gas, and 22,500,000 Btus per short ton of coal. A Btu is about of a food calorie or a kilocalorie, 1,000 Btus contain the energy content of a candy bar. 

European combustion equipment utilizes metric units but these are frequently non-Sl. For example, heat and power ratings often use calories and kilocalories/h instead of joules and watts. 

A 12-oz can of most colas has about 120 nutritional calories (1 nutritional calorie = 1 kilocalorie). Approximately how many minutes of walking are required to bum up as energy foe calories taken in after drinking a can of cola (Walking uses up about 250 kcal/h.)... 

Prior to the now almost universal adoption of the SI system of units, the unit of heat was defined as the quantity of heat required to raise the temperature of unit mass of water by one degree. This heat quantity is designated the calorie in the cgs system and the kilocalorie in the mks system, and in both cases temperature is expressed in degrees Celsius (Centigrade). As the specific heat capacity is a function of temperature, it has been necessary to set a datum temperature which is chosen as 298 K or 25°C. 

The nutritional calorie, Cal, is actually 1 kilocalorie (kcal), and so it is important to note which unit is being used when assessing the energy content of food. 

The use of non-SI units is strongly discouraged. For these units there often do not exist standards, and for historical reasons the same denomination may mean sundry units. For example, it is common practice in theoretical chemistry to state energy values in kilocalories. However, to convert a calorie to the SI unit Joule, there exist different conversion factors ... 

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). 

This is not the same calorie that is commonly associated with food and diets. That is the nutritional Calorie, which is really a kilocalorie (1 C = 1000 cal). 

By convention, AG is negative for a spontaneous reaction. The SI units are joule per mole G/mol). Other common units are calories per mole (cal/mol, where 1 cal = 4184J) and kilocalories per mole (kcal/mol), where 1000 cal = Ikcal. As shown next, AG of a reaction can be calculated from various types of thermodynamic data. The more negative the AG, the more lavored the reaction and the greater the amount of energy that can be released to the surroimdings. 

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. 

Perform both calculations now to make sure that you understand how they were done. Notice that the energy units for the values differ hy a factor of 1,000 in the calculations that follow, AS is divided by 1,000 to make the terms comparable, converting calories to kilocalories. 

The units calorie (cal) and kilocalorie (kcal) are no longer be used. 

Most thermochemical data are found with the calorie as the unit, and it will be used in this book in most instances. Some typical AH values for pyrotechnics are given in Table 2.6. Note 1 kcal = 1 kilocalorie = 1,000 calories. 

Table 3.3 gives some relationships between commonly used energy units. Today the SI system of units is in general use, although much of the data in the literature is in the older units. Thus we use both types of units for energy, that is calories or kilocalories and joules or kilojoules, where 1 cal = 4.184 J. 

Note that a food calorie actually refers to a Calorie, which is a kilocalorie — a calorie of cheesecake is 1,000 times larger than you think it is. 

The energy of radiation is quite often expressed in terms of kilocalorie per mole (kcal/mole), (I calorie = 4-186 J). Sometimes, merely cm-1, the unit of wavenumber is used to express energy. The proportionality constant he, is implied therein. The unit of electron-volt (eV) is used for single atom or molecule events. A chemical potential of one volt signifies an energy of one electron volt per molecule. 

---