An over riding energy concept is that energy is conserved. The law of conservation of energy says "Energy is neither created nor destroyed".

Energy is only transferred and dissipated. High concentrations of energy are useful. Low concentrations of energy are less useful. Flames are examples of high concentrations of energy.

Energy in the form of heat moves from flames to cooler objects where there is a low concentration of energy.

Energy is one of the most important quantites in science and life. Physical and chemical changes naturally occur when they go to a condition of low or minimum energy.

Water runs down hill because it is moving to lower potential energy. Water has less potential energy at the bottom of a hill. Gravity determines the potential energy of the water. Water at higher elevations has higher potential energy because it has the potential to run downhill. When the water flows downhill the potential energy decreases and is dissipated as kinetic energy. Eventually at sea level the water reaches a level with relative zero potential energy.

MEASURING ENERGY: Energy units are calories, Kilocalories, and Joules. One calorie is the amount of heat needed to warm 1 gram of water by one degree Celsius. A kilocalorie is 1000 calories.  The dietetic calorie or big calorie equals  1 kilocalorie = 1 Calories  . Click here for a list of foods and their Calorie content. An example is 1 ounce or a 1 1/4 cup serving of Cheerios 110 Calories.  This is 110,000 small calories.

There are many forms of energy. These forms are thermal energy, electrical energy, sound energy, light energy, etc are all different ways we observe kinetic and potential energy. 

There are two classes of energy, kinetic energy and potential energy. The total energy for everything is the sum of these two. Thermal energy, electrical energy, sound energy, light energy, etc are all different ways we observe kinetic and potential energy.