Definition of energy by expert - The concept of energy plays an important role in all of the sciences. In chemistry all physical and chemical changes have energy considerations associated with them. To understand how and why these changes happen, an understanding of energy is required.
Energy is defined as the capacity to do work. Work is done whenever a force is applied over a distance. Thus anything that can force matter to move, to change speed, or to change direction has energy. The following example will help you understand this definition of energy. When you charge a battery with electricity, you are storing energy in the form of chemical energy. The charged battery has a capacity to do work. If you use the battery to operate a toy car, the energy stored is transformed into mechanical energy which exerts a force on the mechanism that turns the wheels and makes the car move. This continues until the "charge" or stored energy is used up. In its uncharged condition, the battery no longer has the capacity to do work.
Just as work itself is measured in joules (J), so is energy. In some problems, it may be expressed in kilocalories (kcal). The relationship between these two units is that 4180 J is equal to 1 kcal.
Forms of Energy
Energy may appear in a variety of forms. Most commonly, energy in reactions is evolved as heat. Some other forms of energy are light, sound, mechanical energy, electrical energy, and chemical energy. Energy can be converted from one form to another, as when the heat from burning fuel is used to vaporize water to steam. The energy of the steam is used to turn the wheels of a turbine to produce mechanical energy. The turbine turns the generator armature to produce electricity, which is then available in homes for use as light or heat or for the operation of many modern appliances.
Two general classifications of energy are potential energy and kinetic energy. Potential energy is due to position; kinetic energy is energy of motion. The difference can be illustrated by a boulder sitting on the side of a mountain. It has a high potential energy because of its position above the valley floor. If it falls, however its potential energy is converted to kinetic energy. This illustration is very similar to the situation of electrons cascading to lower energy levels in the atomic model.
This concept can also be applied at the molecular level. For example, the molecule of N2 molecule. To break this bond would require energy. The potential energy in each isolated atom of nitrogen would then be greater. This would be similar to raising he boulder to a higher position on the mountainside. Both systems have a higher potential energy and have a tendency to fall back to the lower state, which is more stable.
Energy is defined as the capacity to do work. Work is done whenever a force is applied over a distance. Thus anything that can force matter to move, to change speed, or to change direction has energy. The following example will help you understand this definition of energy. When you charge a battery with electricity, you are storing energy in the form of chemical energy. The charged battery has a capacity to do work. If you use the battery to operate a toy car, the energy stored is transformed into mechanical energy which exerts a force on the mechanism that turns the wheels and makes the car move. This continues until the "charge" or stored energy is used up. In its uncharged condition, the battery no longer has the capacity to do work.
Just as work itself is measured in joules (J), so is energy. In some problems, it may be expressed in kilocalories (kcal). The relationship between these two units is that 4180 J is equal to 1 kcal.
Forms of Energy
Energy may appear in a variety of forms. Most commonly, energy in reactions is evolved as heat. Some other forms of energy are light, sound, mechanical energy, electrical energy, and chemical energy. Energy can be converted from one form to another, as when the heat from burning fuel is used to vaporize water to steam. The energy of the steam is used to turn the wheels of a turbine to produce mechanical energy. The turbine turns the generator armature to produce electricity, which is then available in homes for use as light or heat or for the operation of many modern appliances.
Two general classifications of energy are potential energy and kinetic energy. Potential energy is due to position; kinetic energy is energy of motion. The difference can be illustrated by a boulder sitting on the side of a mountain. It has a high potential energy because of its position above the valley floor. If it falls, however its potential energy is converted to kinetic energy. This illustration is very similar to the situation of electrons cascading to lower energy levels in the atomic model.
This concept can also be applied at the molecular level. For example, the molecule of N2 molecule. To break this bond would require energy. The potential energy in each isolated atom of nitrogen would then be greater. This would be similar to raising he boulder to a higher position on the mountainside. Both systems have a higher potential energy and have a tendency to fall back to the lower state, which is more stable.
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