THE DEFINITION OF ENERGY.

• Energy is defined as the capacity to do work (W) • W = applied force (f) x distance (d) • Distance over which motion occurs • Movement must be in same direction as force Heat Energy • Thermal energy or heat can be determined indirectly by knowing the specific heat capacity (C H) of the object heated and its temperature (T) that is characterized by the average kinetic energy of atoms or molecules. Heat (kJ) = C H (kJ/g-°C) x mass (g) x ∆T (°C) • Temperature can be measured in K, °C, or °F. K = 273 + °C and °C = (°F-32)/1.8 • As heat is applied, atoms or molecules gain kinetic energy and become further apart. • Joule and calories are the more common units for energy • 4.184 joule (J) = 1 calorie • One calorie is the amount of heat needed to raise the temperature of 1 gram of pure liquid water by 1 °C • Temperature is a property that determines the direction of heat flow; heat flows from a hotter to a colder body. • Measure of heat or thermal energy • 1 kcal = 1000 calories • Calorie = 1 kcal (Cal ≠ cal) • Calorie = food or nutritional calorie • Other energy units are British Thermal Units, ergs, & foot-pounds.