Capacity to perform work:
Energy is defined as the capacity to perform work or produce change. This means that when there is energy, objects can be moved, heat can be generated, light can be emitted, etc.
Immutability (Law of Conservation of Energy):
Energy cannot be created or destroyed; it only transforms from one form to another. For example, the chemical energy in food is transformed into mechanical energy when we walk or run.
Diversity of forms:
Energy can exist in different forms, such as kinetic (motion), potential (position), thermal (heat), chemical, electrical, nuclear, and more. Each form of energy can be converted into another.
Transferability:
Energy can be transferred from one object or system to another. For example, when two objects collide, the kinetic energy of one can be transferred to the other.
Dependence on matter:
Energy is related to matter. For instance, the potential energy of an object depends on its mass and its position in a gravitational field.
Scalar quantity:
Energy is a scalar quantity, meaning it only has magnitude and no direction, unlike a vector quantity like force.
Measured in Joules:
In the International System (SI), energy is measured in Joules (J). One joule is the amount of work done when a force of one newton is applied to an object and moves it a distance of one meter.
Conservative property:
In closed systems (where there is no exchange of energy with the surroundings), the total amount of energy remains constant over time.
Capacity for transformation:
Energy can change from one form to another. For example, a battery transforms chemical energy into electrical energy, which can then be converted into light and thermal energy when a bulb is lit.
Efficiency in use:
Not all transferred or transformed energy is used to perform the desired work; some of it may dissipate as heat, sound, etc. This refers to the efficiency of a process.