Not only had the peanut heated the water from room temperature to 100 degrees Celsius, it had also boiled away two grams of water. Heat flowed from that burning peanut as combustion converted the hidden chemical energy stored in the nut into the easily measured energy of heat flow. As professor Benedek's demonstration showed, a little bit of food stores a great deal of energy in its chemical bonds. More energy than a stick of Dynamite Physicists and dieters are both concerned with the energy contained in food. And they both count calories.
Physicists measure the energy content of food by burning the food.
To a physicist, a calorie is the heat flow needed to raise the temperature of one gram of water by one degree Celsius. After burning that peanut, professor Benedek turned to the blackboard and calculated the calories that the peanut had produced. This temperature increase required 800 calories of heat flow. The heat flowing from the peanut then boiled away two grams of water, which took 1080 calories more, since 540 calories are needed to boil a gram. All in all, one burning peanut delivered 1880 calories to the test tube of water.