<P> A calorie is a unit of energy . Various definitions exist but fall into two broad categories . The first, the small calorie, or gram calorie (symbol: cal), is defined as the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere . The second is the large calorie or kilogram calorie (symbol: Cal), also known as the food calorie and similar names, is defined in terms of the kilogram rather than the gram . It is equal to 7003100000000000000 ♠ 1000 small calories or 1 kilocalorie (symbol: kcal). </P> <P> Although these units relate to the metric system, all of them have been considered obsolete in science since the adoption of the SI system . The unit of energy in the International System of Units is the joule . One small calorie is approximately 4.2 joules (so one large calorie is about 4.2 kilojoules). The factor used to convert calories to joules at a given temperature is numerically equivalent to the specific heat capacity of water expressed in joules per kelvin per gram or per kilogram . The precise conversion factor depends on the definition adopted . </P>

A food calorie is equivalent to which metric measurement of heat
find me the text answering this question