7. Law of Conservation of Energy
The law of conservation of energy states that when one form of energy is transformed to another, no energy is destroyed in the process. According to the law of conservation of energy, energy cannot be created or destroyed. So the total amount of energy is the same before and after any transformation. If you add up all the new forms of energy after a transformation, all of the original energy will be accounted for.
Mechanical Energy
Think about the pass thrown by the quarterback. A football thrown by a quarterback has mechanical energy. So does a moving car or a trophy on a shelf. The form of energy associated with the position and motion of an object is called mechanical energy.
Think about the pass thrown by the quarterback. A football thrown by a quarterback has mechanical energy. So does a moving car or a trophy on a shelf. The form of energy associated with the position and motion of an object is called mechanical energy.
But an object can have other forms of kinetic and potential energy. Most of these other forms are associated with the particles that make up objects. These particles are far too small to see. Forms of energy associated with the particles of objects include thermal energy, electrical energy, chemical energy, nuclear energy, and electromagnetic energy.
If you’ve ever eaten ice cream on a hot day, you’ve experienced thermal energy. Fast-moving particles in the warm air make the particles of ice cream move faster. As the kinetic energy of the particles increases, so does the thermal energy of the ice cream. Eventually, the ice cream melts.
When you receive a shock from a doorknob you are receiving electrical energy.
When you receive a shock from a doorknob you are receiving electrical energy.
Chemical Energy
Almost everything you see, touch, or taste is composed of chemical compounds. Chemical compounds are made up of atoms and molecules. Bonds between the atoms and molecules hold chemical compounds together. These bonds have chemical energy. Chemical energy is potential energy stored in the chemical bonds that hold chemical compounds together. Chemical energy is stored in the foods you eat, in the matches you can use to light a candle, and even in the cells of your body. When bonds in chemical compounds break, new chemical compounds may form. When this happens, chemical energy may be released.
Almost everything you see, touch, or taste is composed of chemical compounds. Chemical compounds are made up of atoms and molecules. Bonds between the atoms and molecules hold chemical compounds together. These bonds have chemical energy. Chemical energy is potential energy stored in the chemical bonds that hold chemical compounds together. Chemical energy is stored in the foods you eat, in the matches you can use to light a candle, and even in the cells of your body. When bonds in chemical compounds break, new chemical compounds may form. When this happens, chemical energy may be released.
What does flowing water have to do with electricity? You may already know that the mechanical energy of moving water can be transformed into electrical energy. Most forms of energy can be transformed into other forms. A change from one form of energy to another is called an energy transformation. Some energy changes involve single transformations, while others involve many transformations.
Single Transformations
Sometimes, one form of energy needs to be transformed into another to get work done. You are already familiar with many such energy transformations. For example, a toaster transforms electrical energy to thermal energy to toast your bread. A cell phone transforms electrical energy to electromagnetic energy that travels to other phones.
Your body transforms the chemical energy in your food to mechanical energy you need to move your muscles. Chemical energy in food is also transformed to the thermal energy your body uses to maintain its temperature.
Multiple Transformations
Often, a series of energy transformations is needed to do work. For example, the mechanical energy used to strike a match is transformed first to thermal energy. The thermal energy causes the particles in the match to release stored chemical energy, which is transformed to thermal energy and the electromagnetic energy you see as light.
In a car engine, another series of energy conversions occurs. Electrical energy produces a spark. The thermal energy of the spark releases chemical energy in the fuel. The fuel’s chemical energy in turn becomes thermal energy. Thermal energy is converted to mechanical energy used to move the car, and to electrical energy to produce more sparks.
Single Transformations
Sometimes, one form of energy needs to be transformed into another to get work done. You are already familiar with many such energy transformations. For example, a toaster transforms electrical energy to thermal energy to toast your bread. A cell phone transforms electrical energy to electromagnetic energy that travels to other phones.
Your body transforms the chemical energy in your food to mechanical energy you need to move your muscles. Chemical energy in food is also transformed to the thermal energy your body uses to maintain its temperature.
Multiple Transformations
Often, a series of energy transformations is needed to do work. For example, the mechanical energy used to strike a match is transformed first to thermal energy. The thermal energy causes the particles in the match to release stored chemical energy, which is transformed to thermal energy and the electromagnetic energy you see as light.
In a car engine, another series of energy conversions occurs. Electrical energy produces a spark. The thermal energy of the spark releases chemical energy in the fuel. The fuel’s chemical energy in turn becomes thermal energy. Thermal energy is converted to mechanical energy used to move the car, and to electrical energy to produce more sparks.
The law of conservation of energy states that when one form of energy is transformed to another, no energy is destroyed in the process. According to the law of conservation of energy, energy cannot be created or destroyed. So the total amount of energy is the same before and after any transformation. If you add up all the new forms of energy after a transformation, all of the original energy will be accounted for.
