Students: meet the fourth state of matter

1. What is a Plasma?

Plasma is often called the fourth state of matter. You already know solids, liquids, and gases. If you heat a gas enough, the atoms break apart into electrons and ions. This “soup” of charged particles is plasma.
It behaves very differently from ordinary gases because it responds to electric and magnetic fields.
Like a gas, it has no fixed shape or volume, but unlike a gas, it is made of charged particles that respond to electric and magnetic fields.

Feature	Natural Plasmas	Laboratory & Industrial Plasmas
Where found	Sun, stars, auroras, lightning, solar wind	Neon lights, plasma TVs, fusion reactors, semiconductor tools, plasma torches
Scale	Gigantic (cosmic) or atmospheric (lightning bolts, auroras)	Small to medium (lab devices, industrial chambers)
Conditions	Very high temperatures, strong fields, violent events (lightning strikes)	Controlled environments: low pressure chambers, atmospheric jets, magnetic confinement
Examples	Lightning during thunderstorms, auroras over the poles, solar flares	Glow discharge tubes, plasma etching, plasma sterilization, fusion experiments
Why important	Explains natural phenomena & space weather; powers the Sun and stars	Enables technology, medicine, and potential fusion energy

Feature	Hot Plasmas	Cold Plasmas (Non-thermal)
Temperature	Millions of °C (both electrons & ions are very hot)	Near room temperature overall, but electrons are hot while ions and gas stay cool
Where found	Sun, stars, solar wind, fusion reactors	Neon lights, plasma TVs, medical plasma jets, industrial processes
Characteristics	Extremely energetic, must be confined by magnetic fields or inertia	Safe to handle in some cases, created at low or atmospheric pressure
Applications	Fusion energy, astrophysics, space science	Sterilization, wound healing, surface cleaning, microchip fabrication
Why important	Model of the universe, future clean energy source	Everyday technologies and biomedical innovation

Fundamental physics: interaction of particles and fields.
Applications: space exploration, clean energy (fusion), environmental & biomedical uses.
Frontier science: “More than 99% of visible matter in the universe is plasma!”

High school:
– Interactive videos (YouTube/ESA/NASA)
– Simulations (PhET “Neon Lights & Other Discharge Lamps”).
Bachelor:
– Intro textbooks: “Introduction to Plasma Physics” by Chen (chapters 1–2).
– Simple lab demos (glow discharge tubes, plasma ball).
Master:
– Advanced courses: kinetic theory, magnetized plasmas.
– Links to online lectures (Coursera, MIT OCW).