What is a Particle? - Definition & Theory

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  • 0:00 Definition Of A Particle
  • 0:49 Particle Properties…
  • 1:56 Atomic Particles
  • 3:06 Subatomic Particles
  • 3:51 Lesson Summary
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Lesson Transcript
Instructor: Sergey Segal

Sergey has a Masters in Biomedical Engineering and has taught science and mathematics courses at the University of Wisconsin-Madison.

Particles are fundamental entities that are used by scientists to explain different types of phenomena. Learn more about them, subsequently testing your knowledge with a quiz.

Definition of a Particle

Imagine picking up a rock and smashing it with a hammer so that it breaks up into smaller fragments. Then, successively break each of the fragments into even smaller fragments, until the resulting pieces are so small that they cannot be further broken down. These non-breakable fragments are one example of particles.

A particle refers to a quantity of matter that is used by scientists to construct theories about their field of study. There is no particular size restriction on defining a particle. Astronomers can define particles to be stars in the night sky, while physicists can define particles to be electrons. It mostly depends on the scientific field and theory under development.

Particles Properties and Classification

You may ask, 'If there is such a large variety of objects that can be thought of as particles, is there a common theme among all of them?' Well, there is, and we will now discuss it.

Scientists often think of particles as point-like objects, meaning that they are considered shapeless for the purposes of the theory. For example, when a chemist is studying the properties of gas particles in a container, he or she would think of them as little shapeless objects that bounce against the walls of their container. If an engineer is studying traffic flow on a busy street, he or she would consider all the vehicles to be particles, disregarding whether a particular vehicle is a bus, car, or motorcycle.

Although all of the previous examples described particles in motion, it is important to note that particles can be permanently stationary objects, at least for the purposes of the theory. For example, the carbon atoms that make up graphite, a primary constituent of pencil lead, can be thought of as particles. Let's briefly discuss atomic and subatomic particles, which are very important in many scientific fields.

Atomic Particles

Democritus, an ancient Greek philosopher, had a thought experiment similar to the example with the rock fragments. If you take any piece of matter and keep dividing it in half, you will eventually reach a point where it could no longer be divided. He called these indivisible particles atoms.

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