The plant made the molecules by using light energy from the Sun. The Sun's light energy came from electrons in its atoms lowering energy states, and releasing energy.
The energy in the atoms came from the nuclear reactions in the heart of the Sun. What started the nuclear reactions? Physicists think the Big Bang did. So the short answer is that the energy we encounter and use everyday has always been with us since the beginning of the universe and always will be with us.
It just changes form all around us. That is called the law of conservation of energy. If they have the same mass, hot atoms and molecules move, on average, faster than cold ones. Even if atoms are locked in a solid, they still vibrate back and forth around some average position. In a liquid, atoms and molecules are free to flow from place to place. Within a gas, they are even more free to move and will completely spread out within the volume in which they are trapped.
Put a pan on a stovetop and turn on the heat. The metal sitting over the burner will be the first part of the pan to get hot. They also vibrate farther back and forth from their average position. As they bump into their neighbors, they share with that neighbor some of their energy. Think of this as a very tiny version of a cue ball slamming into other balls during a game of billiards. As a result of collisions with their warmer neighbors, atoms start moving faster.
In other words, they are now warming. These atoms, in turn, transfer some of their increased energy to neighbors even farther from the original source of heat.
This conduction of heat through a solid metal is how the handle of a pan gets hot even though it may be nowhere near the source of heat. Energy can be transferred from one object to another by doing work.
To do work requires that an agent exert a force on an object over a distance. When work is done, energy is transferred from the agent to the object, which results in a change in the object's motion more specifically, a change in the object's kinetic energy. Suppose that a person the agent exerts a force on a wheelbarrow the object that is initially at rest, causing it to move over a certain distance. Recall that the work done on the wheelbarrow by the person is equal to the product of the person's force multiplied by the distance traveled by the wheelbarrow.
Notice that when the force is exerted on the wheelbarrow, there's a change in its motion. Its kinetic energy increases. But where did the wheelbarrow get its kinetic energy? It came from the person exerting the force, who used chemical energy stored in the food they ate to move the wheelbarrow.
In other words, when the person did work on the wheelbarrow, they transferred a certain amount of chemical energy to the wheelbarrow, causing it to move. Energy can also be transferred from place to place by electric currents, which can then be used locally to produce motion, sound, heat, or light. The currents may have been produced to begin with by transforming the energy of motion into electrical energy e.
By the end of grade 8. When the motion energy of an object changes, there is inevitably some other change in energy at the same time. For example, the friction that causes a moving object to stop also results in an increase in the thermal energy in both surfaces; eventually heat energy is transferred to the surrounding environment as the surfaces cool. Similarly, to make an object start moving or to keep it moving when friction forces transfer energy away from it, energy must be provided from, say, chemical e.
The amount of energy transfer needed to change the temperature of a matter sample by a given amount depends on the nature of the matter, the size of the sample, and the environment. Energy is transferred out of hotter regions or objects and into colder ones by the processes of conduction, convection, and radiation.
By the end of grade Conservation of energy means that the total change of energy in any system is always equal to the total energy transferred into or out of the system. Energy cannot be created or destroyed, but it can be transported from one place to another and transferred between systems.
Mathematical expressions, which quantify how the stored energy in a system depends on its configuration e. The availability of energy limits what can occur in any system. Uncontrolled systems always evolve toward more stable states—that is, toward more uniform energy distribution e. Any object or system that can degrade with no added energy is unstable.
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