What Does It Mean to Measure Energetic Change?
Energy is what allows things to happen. It gives objects the capacity to move, change, heat up, or transform. Whenever something changes — a car rolling downhill, a ball bouncing, a fire burning — energy is being transferred or converted from one form to another.
Measuring how much energy changes in a process is at the heart of understanding physics and chemistry. In this subtopic, we will explore how to calculate and track energetic changes using formulas, and how the law of conservation of energy governs all these transformations.
Energy changes happen in two broad contexts: mechanical systems (moving objects) and thermal/chemical systems (heating and reactions). The same fundamental principle — conservation of energy — applies to both.
Think of energy like money in a bank account. You can move it between accounts (transfer it) or spend it on different things (convert it to another form), but the total amount in the system never disappears — it just goes somewhere else.
Key Energy Forms: Kinetic and Potential
Two of the most important forms of energy in mechanics are kinetic energy and potential energy.
The energy possessed by an object because it is moving. The faster an object moves and the more mass it has, the more kinetic energy it possesses.
A stored form of energy possessed by an object due to its height above the ground. The higher and heavier the object, the more gravitational potential energy it has.
A stored form of energy in a stretched or compressed object, such as a spring, elastic band, or bent bow. When released, this stored energy converts into kinetic energy.
Energy stored in the bonds between atoms in substances such as fuels, food, and batteries. This energy is released or absorbed during chemical reactions.
Kinetic and gravitational potential energy are constantly converting into one another in everyday situations:
- A ball thrown into the air converts kinetic energy → gravitational potential energy as it rises.
- As the ball falls back down, gravitational potential energy → kinetic energy.
- A car rolling down a hill converts gravitational potential energy → kinetic energy.
- A stretched spring converts elastic potential energy → kinetic energy when released.
Rolling car on a hill: A driver forgets to apply the brakes and a car begins to roll down a hill. As the car moves downward, it loses gravitational potential energy and gains kinetic energy — it speeds up as it descends.
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