SSC
Which state of matter is often called the 'fourth state of matter'?
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Answer: Option B — Plasma
Detailed Solution
The three familiar states of matter are solid, liquid and gas. Plasma is called the fourth state of matter. It is an ionised gas, made up of free electrons and positively charged ions, along with some neutral atoms. It is formed when a gas is heated to a very high temperature, or exposed to a strong electric field, so that electrons are knocked out of the atoms.
Although plasma contains charged particles, it is electrically neutral overall, because the numbers of positive and negative charges are roughly equal. Because the particles are charged, plasma conducts electricity well and is strongly affected by electric and magnetic fields. It often glows, giving off light.
The term "plasma" was introduced by the American scientist Irving Langmuir in 1928. Sir William Crookes had earlier described it as "radiant matter" in 1879.
Plasma is the most common state of visible matter in the universe. Examples include:
- The Sun and other stars, which are huge balls of hot plasma.
- Lightning.
- The aurora borealis and aurora australis (northern and southern lights), caused by charged particles from the Sun interacting with the Earth's upper atmosphere.
- The Earth's ionosphere.
- Fluorescent tube lights, neon signs and plasma television screens.
- The interior of nuclear fusion reactors (such as tokamaks), where hydrogen plasma is heated to millions of degrees.
A fifth state of matter, the Bose-Einstein condensate (BEC), forms when a gas of certain atoms is cooled to temperatures very close to absolute zero. The atoms then behave as a single "super-atom". It was predicted by Satyendra Nath Bose and Albert Einstein in 1924-25, and first created in a laboratory in 1995 by Eric Cornell and Carl Wieman, who shared the Nobel Prize in Physics in 2001 with Wolfgang Ketterle. The particles called bosons are named after S.N. Bose.
Why not the other options?
- ✗Bose-Einstein condensate is called the fifth state of matter.
- ✗Liquid crystals have properties between liquids and solid crystals; they are used in LCD screens.
- ✗A colloid is a mixture, not a state of matter.
Quick tip
Remember: Plasma = fourth state (ionised gas: Sun, lightning, aurora, neon signs; term by Langmuir, 1928); Bose-Einstein condensate = fifth state (near absolute zero, S.N. Bose).
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Matter & Its States — Preparation
This question tests your understanding of Matter & Its States, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers matter and its classification: the states of matter, changes of state (melting, evaporation, sublimation and condensation), elements, compounds and mixtures, solutions, colloids and suspensions, and methods of separating mixtures. Exam questions often ask about examples of sublimation (camphor, naphthalene and dry ice), which substances are colloids (milk, fog and blood), and which method separates which mixture, such as chromatography for the colours in ink and fractional distillation for crude oil. Know the difference between a physical change and a chemical change. Practise the matter and its states questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.