Antimatter

Definition

Antimatter consists of particles that are counterparts to the particles of ordinary matter, but with opposite charge and quantum properties. When antimatter meets matter, they annihilate each other, releasing energy.

5 Must Know Facts For Your Next Test

1. Antiparticles have the same mass as their corresponding particles but opposite charges; for example, the positron is the antiparticle of the electron.
2. Antimatter can be produced in high-energy processes such as cosmic ray interactions or particle accelerators.
3. When a particle and its corresponding antiparticle collide, they annihilate to produce photons or other particle-antiparticle pairs.
4. The existence of antimatter was first theorized by Paul Dirac in 1928 and confirmed experimentally in 1932 with the discovery of the positron by Carl Anderson.
5. Conservation laws, such as conservation of charge and conservation of baryon number, apply to reactions involving antimatter just as they do for matter.

Review Questions

• What happens when a particle collides with its corresponding antiparticle?
• Who first theorized the existence of antimatter and who discovered it experimentally?
• How do conservation laws apply to reactions involving antimatter?

Related terms

Positron:

The antiparticle of the electron; it has the same mass as an electron but a positive charge.

Annihilation:

A process where a particle and its antiparticle collide and convert their mass into energy, typically producing photons.

Pair Production: A phenomenon where energy is converted into a particle-antiparticle pair, usually an electron and a positron.