100 Fun Facts About States of Matter

Which everyday sight is plasma, the fourth state of matter?

Lightning is plasma: in a split second the bolt heats the air in its path to around 30,000 °C, and that air's explosive expansion is the thunder.

Particles in a liquid stay close but slide past each other, so a liquid keeps what?

Its volume but not its shape: with no container at all, a small falling raindrop is not a teardrop but a tiny ball, and bigger ones flatten like a burger bun.

Which property of water lets a water strider walk across a pond without sinking?

Surface tension: water molecules cling to one another so strongly that the top layer acts like a stretched skin, and the insect's long legs spread its weight across it.

Propane is a gas at room temperature, so what keeps it liquid inside a barbecue tank?

High pressure holds the propane as a liquid; open the valve and, as the pressure falls, it boils back into the gas that feeds the flame.

What does plasma contain that an ordinary gas lacks?

Free-moving charged particles make a plasma respond to magnets, which lets fusion researchers confine it with magnetic fields and heat it hotter than the heart of a star.

Which everyday technology uses matter that flows like a liquid but stays ordered like a crystal?

LCD screens: the letters stand for liquid-crystal display, and a weak electric field is enough to realign the crystals, which is how early ones showed digits on calculators and watches.

Which of these is almost all plasma, the universe's commonest state of ordinary matter?

The Sun is a ball of plasma with no solid surface at all, and since the other stars and the thin gas between them are plasma too, plasma far outweighs solids, liquids and gases.

Which ultra-light solid, about 99.8% empty space, did NASA's Stardust probe use to catch comet dust?

Aerogel is a gel whose liquid has been swapped for air; though made of the same silica as window glass, the Stardust blocks were about 1,000 times less dense.

Which scientist, whose glowing vacuum tubes bear his name, called their contents a 'fourth state of matter' in 1879?

William Crookes took the glowing rays in his tubes for 'radiant matter'; in 1897 J. J. Thomson showed they were streams of a new particle, the electron.

The word "gas" was coined by which chemist, born decades before Robert Boyle?

Jan Baptist van Helmont, a Flemish physician, noticed that burning charcoal and fermenting grape juice gave off the same 'wild spirit', which he named gas sylvestre.

The word "gas" is thought to be a transcription of which Ancient Greek word?

Chaos, in its old sense of empty space, is the probable root: a Dutch g sounds much like the Greek kh, so the word may simply be chaos as its coiner said it.

Unlike a liquid, a gas is described as what kind of fluid?

Compressible: the molecules of a gas are so far apart that it can be squeezed into a fraction of its volume, while a liquid's molecules already touch and barely give.

Which of these is a noble gas made of single atoms?

Neon's atoms have a full outer shell of electrons, so they neither pair up nor react, while oxygen, nitrogen and chlorine all go around as two-atom molecules.

Gas particles spreading out to fill a container evenly is called what?

Diffusion is why a scent released in one corner soon reaches the far side of a still room, though endless collisions with air molecules slow each molecule's trip.

Boyle's, Charles's and Avogadro's laws combine into which single equation, PV = nRT?

The ideal gas law describes an imaginary gas whose molecules neither attract nor repel one another; no real gas is ideal, but most come close under everyday conditions.

A solid turning directly into a gas, as dry ice does, is called what?

Sublimation is also why old mothballs shrink away to nothing, and why snow can vanish from the ground on a dry, sunny winter day without ever melting.

Dry ice is the solid form of which substance?

Carbon dioxide has no liquid form at everyday air pressure, so a block of it shrinks straight into cold gas and leaves no puddle behind: hence 'dry' ice.

Which of these is far colder than dry ice's −78.5 °C?

Liquid nitrogen boils at −196 °C, more than a hundred degrees below dry ice, which is why clinics use it to freeze off warts and labs to store living cells.

Which preservation method removes water by turning ice straight to vapour under a vacuum?

Freeze-drying leaves food light and long-lasting because the ice leaves as vapour without ever wetting it, which is why hikers and astronauts carry their meals this way.

Water vapour turning directly into frost without becoming liquid is an example of what?

Deposition also builds snowflakes: high in a cloud, water vapour freezes straight onto an ice crystal that began around a speck of dust or pollen.

Condensation, a gas turning into liquid, is the reverse of which process?

Vaporization covers both boiling and evaporation; run it backwards and you get the fog on a pair of glasses or the drips on a cold window pane.

Where on a liquid does evaporation take place?

At its surface, and at any temperature; boiling is different because vapour bubbles form inside the liquid, which happens only once it is hot enough.

Why does sweating cool you down?

Evaporating molecules carry energy away, which is why sweat cools you poorly on a humid day: the damp air slows evaporation from your skin.

Why does water boil at a cooler temperature up a mountain?

Lower pressure in the thin mountain air lets water boil at only about 70 °C on top of Everest, so a three-minute egg can take far longer up there.

Which black substance, brittle enough to shatter under a hammer, has been dripping from a Queensland funnel since 1930?

Pitch flows so slowly that just nine drops fell in the experiment's first 87 years, and the professor who tended it for 52 of them never saw one fall.

Which metal has the highest melting point of all?

Tungsten stays solid to about 3,400 °C, which is why it was drawn into the white-hot filaments of incandescent light bulbs.

Deep inside Jupiter, crushing pressure is thought to turn hydrogen into what unusual form?

A liquid metal: the pressure strips electrons from the hydrogen atoms so that it conducts electricity, and its motion is thought to drive Jupiter's huge magnetic field.

Which is the only metal that is liquid at standard temperature and pressure?

Mercury stays liquid down to about −39 °C, and its old name quicksilver means 'living silver', after the way the bright metal runs about.

Which metal melts in the palm of your hand, at just under 30 °C?

Gallium's low melting point was predicted by Mendeleev, who left a gap for the element in his periodic table four years before anyone had found it.

Which non-metal element is liquid at room temperature?

Bromine is a dark red-brown liquid whose choking fumes gave it its name, from the Greek bromos, 'stench'.

Besides Earth, which world in the Solar System has standing lakes and seas of liquid on its surface?

Titan's lakes and seas hold liquid methane and ethane rather than water: it is so cold on Saturn's largest moon, about −179 °C, that methane falls as rain.

Why does ice float on water?

It is less dense than liquid water because freezing locks the molecules into an open lattice that takes up more room, which is also why a frozen pipe can burst.

Liquid water is densest at what temperature?

4 °C water is the heaviest, so in winter it sinks to the bottom of a lake while colder water and ice stay on top, which is why lakes freeze from the surface down.

Almost all ice on Earth has which crystal structure?

Hexagonal: the six-fold lattice, known as ice Ih, is the reason every snowflake grows six sides or six arms.

At its triple point, which three phases of a substance coexist in equilibrium?

Solid, liquid and vapour meet for water at 0.01 °C and about 0.6% of normal air pressure; any lower and ice can no longer melt, only pass straight into vapour.

Before 2019, the triple point of water was used to define which SI unit?

The kelvin was tied to water's triple point because it is far easier to reproduce than a freezing point; since 2019 the unit has been defined through the Boltzmann constant instead.

Absolute zero is equivalent to what on the Celsius scale?

−273.15 °C is the floor of the temperature scale: nothing can be colder, because at that point matter has no more heat energy left to give up.

Which law of thermodynamics implies absolute zero cannot be reached in a finite number of steps?

Third: the nearer a system gets to absolute zero, the harder each further step becomes; in 2018 a team in Bremen stopped just 38 trillionths of a degree short.

How was rubidium gas turned into the first Bose–Einstein condensate?

Extreme cooling, almost to absolute zero, dropped the atoms into the same lowest energy state, where they began, in one much-quoted phrase, to 'sing in unison'.

Oobleck, a thick mix of cornstarch and water, turns hard for a moment when you do what?

Tap it sharply and the starch grains jam together like a solid; ease a hand in slowly and they slide apart, letting your fingers sink as if into water.

Cornell, Wieman and Ketterle shared which award in 2001 for making condensates?

Nobel Prize in Physics: the 2001 award came only six years after the first condensate was made, seventy years after Einstein had predicted that it could exist.

A superfluid is a fluid with what remarkable property?

Zero viscosity means a superfluid flows with no resistance at all: stir it and the whirlpool can keep turning indefinitely.

Superfluidity was discovered in 1937 in which element?

Helium is the one element that never freezes at normal pressure however cold it gets, which let Pyotr Kapitsa study it as a liquid within a few degrees of absolute zero.

What marks out a supercritical fluid, formed above a substance's critical point?

No distinct liquid and gas phases: above the critical point the boundary vanishes, leaving one fluid that seeps through solids like a gas yet dissolves things like a liquid.

Supercritical CO2 is widely used industrially to do what?

Decaffeinate coffee: under about 300 times atmospheric pressure the CO2 soaks into green beans and dissolves their caffeine, then turns back to gas and leaves almost no residue.

Glass is an example of what kind of solid?

Amorphous: the old tale that cathedral windows are thicker at the bottom because glass slowly flows is a myth; its atoms move far too slowly for that.

Salting icy roads works because of which effect?

Freezing-point depression is also why the sea stays liquid to about −2 °C and why car radiators are filled with antifreeze.

Which collapsed stellar remnants contain matter at nuclear density?

Neutron stars squeeze about one and a half times the Sun's mass into a ball some 20 km across, so a sugar cube of the stuff would weigh about a billion tons.

Scientists recreate quark–gluon plasma by colliding what?

Lead nuclei, smashed together at CERN, melt into the soup of quarks and gluons that filled the universe for a few millionths of a second after the Big Bang.

In a crystalline solid, how are the particles arranged?

In a regular repeating pattern, which is why crystals grow flat faces and sharp angles: a grain of table salt is a tiny cube because its ions are stacked in a cubic grid.

Oobleck, a goo that turns solid when punched, is made by mixing water with which kitchen powder?

Cornstarch makes the mix thicken under sudden force, so it briefly acts like a solid. A person can walk across a big tub of it without sinking, as long as every step is quick.

Which gas giant is the only planet in the Solar System that is less dense than water?

Saturn is about 30% less dense than water, even though it is over 95 times as massive as Earth. An ocean big enough to hold it could, in theory, float it.

Which weather event heats a narrow channel of air into plasma at more than 25,000 °C?

Lightning heats the air so fast that it bursts outward, and that shock wave is the thunder that follows. The plasma channel can stretch over 5 km from cloud to ground.

Which metal is so malleable that a single gram can be beaten into a sheet covering one square metre?

Gold is the most malleable metal of all. Gold leaf can be beaten so thin that light shines through it, and the light that gets through looks greenish-blue.

Which property of water lets water striders and other small insects stand on a pond without sinking?

Surface tension makes the top of the water behave like a stretched skin. It can even hold up a steel razor blade laid flat, although steel is far denser than water.

The white cloud puffing from a boiling kettle's spout is actually made of what?

Tiny water droplets form where the kettle's invisible steam meets cooler air. True steam is a colourless gas that cannot be seen at all.

Which black substance has dripped about once a decade in a Queensland funnel experiment since 1927?

Pitch looks and feels solid, yet it is a liquid roughly 230 billion times thicker than water. The experiment was set up to show students that some solid-looking things flow.

Which ultralight solid, nicknamed frozen smoke, can be more than 99% air?

Aerogel was first made in 1931 by Samuel Kistler, on a bet that he could swap the liquid in a jelly for gas without the jelly shrinking.

Which of these foods is a shear-thinning liquid, flowing far more easily once it has been shaken?

Ketchup gets runnier when shaken, which is why a stubborn bottle can suddenly flood the plate. Scientists call liquids that change like this non-Newtonian.

Which soft, slippery grey material is built from the same atoms as diamond, stacked in sheets?

Graphite has sheets that slide apart so easily they rub off onto paper as pencil marks, while diamond locks the very same atoms into a rigid cage.

Scientists define matter as anything that has mass and also does what?

Takes up space is the second half of the test, which is why light and heat are not matter: they have no mass and fill no room. Air passes, even though it is invisible.

Particles packed into a solid cannot change places, yet they never stop doing what?

Vibrating about a fixed spot is all a solid's particles can do. Add heat and they shake harder, until the solid finally loses its shape and melts.

Which kitchen appliance cooks food faster by trapping steam so that water boils well above 100 °C?

Pressure cooker designs go back to 1679, when French physicist Denis Papin built a sealed pot he called a steam digester to cut cooking times.

Which gas is chilled into a liquid at −196 °C to flash-freeze food and remove warts?

Nitrogen boils at about −196 °C, so the liquid chills anything it touches almost instantly. Chefs pour it over desserts to set them at the table within moments.

Which black volcanic rock is a natural glass, formed when lava cools too fast for crystals to grow?

Obsidian breaks into edges so sharp that it was once chipped into cutting tools, and it has even been tried out as a surgical scalpel blade.

Why do engineers leave small gaps between lengths of railway track and in the decks of long bridges?

Heat makes materials expand, so a track laid tight in winter has nowhere to go in summer. Without the gaps, rails can buckle sideways on a hot day, a fault known as sun kink.

Aboard the International Space Station, a floating blob of water pulls itself into which shape?

A sphere wraps the water in the least possible skin. On Earth, weight squashes a big drop out of shape, but in orbit nothing stops the blob rounding up into a ball.

While a block of ice is melting, what happens to the temperature of the ice-and-water mixture?

It stays the same, at 0 °C, until the last sliver has melted. The heat goes into pulling the ice apart instead of warming it, energy that the Scottish chemist Joseph Black named latent heat.

Which moon is the only world besides Earth known to have stable lakes and seas on its surface?

Titan has lakes and seas of liquid methane and ethane instead of water, because its ground sits at about −179 °C. It even has rain, rivers and deltas.

Which Greek philosopher, a pupil of Leucippus, proposed that all matter is made of indivisible atoms?

Democritus was nicknamed the laughing philosopher for the value he placed on cheerfulness. The Greek word behind atom, atomon, means uncuttable.

Tanzanian schoolboy Erasto Mpemba noticed that a hot mixture froze before a cold one while making what?

Ice cream was his cookery-class project in 1963. A visiting physicist, Denis Osborne, thought the boy was mistaken, ran the test himself and confirmed what is now called the Mpemba effect.

Temperature is a measure of the average amount of which energy carried by a substance's particles?

Kinetic energy is the energy of movement, so a hot drink is simply one whose particles are moving faster. Cooling it slows them down.

Which French chemist confirmed that mass is neither created nor destroyed in a chemical reaction?

Antoine Lavoisier made the principle famous after careful weighing in the 1770s. Reactions run inside sealed glass vessels showed that the total weight never changed.

Which inventor built the first plasma lamp in the 1890s while testing high-voltage currents?

Nikola Tesla patented his lamp in 1894. The swirling plasma globe sold as a desk toy is a later redesign by James Falk and MIT student Bill Parker.

Which kind of mixture, found in milk and vinaigrette, takes its name from a Latin verb meaning to milk?

Emulsion means two liquids that normally refuse to blend, such as oil and water, with one broken into tiny beads spread through the other. In milk, the beads are fat.

Which unseen substance, detected only by its gravity, is thought to make up 85% of the universe's mass?

Dark matter is the leading explanation for why the outer edges of galaxies such as Andromeda spin faster than their visible stars and gas can account for.

Which layer of Earth stays solid at around 5,400 °C because the weight above squeezes it so hard?

The inner core is about as hot as the surface of the Sun, yet pressure holds its metal solid. The layer just outside it, under less squeeze, is liquid.

Which jittery movement of pollen particles in water did Einstein explain in 1905 as proof of atoms?

Brownian motion is named after botanist Robert Brown, who saw it through a microscope in 1827 but could not explain it. The specks are being jostled by unseen water molecules.

Which eerie blue glow of plasma on ships' masts was often taken by sailors as a good omen?

St. Elmo's fire is named after Erasmus of Formia, the patron saint of sailors. It appears when a strong electric field makes the air around a pointed object glow.

Glass does not flow, so why are old cathedral windows often thicker at the bottom?

Uneven sheets when first made are to blame: the ripples and sags were there on day one. A 2017 study put the flow of medieval glass at about one nanometre per billion years.

Which pungent wardrobe pest-repellent slowly shrinks as it turns straight from a solid into a gas?

Mothballs give off a gas that is toxic to moths and their larvae. That is why clothes are sealed in with them: in an open wardrobe the fumes would simply drift away.

The pressure of the air inside a pumped-up tyre comes from gas molecules constantly doing what?

Bouncing off the walls is the whole story: each tiny collision gives a push, and together the pushes add up to pressure. Pump in more air and the tyre firms up.

Seen under a magnifying glass, grains of ordinary table salt are tiny crystals of which shape?

Cubes appear because salt's sodium and chlorine atoms stack in a boxy grid, so each grain you can see copies the shape of an arrangement you cannot.

Which sweet food is tempered because its fat can set in six crystal forms, only one glossy and snappy?

Chocolate gets its snap and shine from Form V, one of the six ways cocoa butter can crystallise. Tempering exists to coax the fat into that single form.

Which soft silvery metal is the least dense of all, light enough to float on both water and oil?

Lithium is the lightest of only three metals able to float on water; the other two are sodium and potassium. It is also the least dense solid element of any kind.

Which inky liquid, invented at NASA in 1963, bristles into spikes when a magnet is brought near?

Ferrofluid was devised by NASA's Steve Papell as rocket fuel that a magnet could pull toward the pump in weightlessness. It is a liquid loaded with nanoscale magnetic particles.

Which Scottish scientist invented the Thermos-style flask around 1892 to store liquefied gases?

James Dewar never patented his flask, so he earned nothing when the Thermos company turned it into a household item, and he even lost a court case over it.

Which doughnut-shaped Soviet invention uses powerful magnets to trap plasma for fusion research?

Tokamak is a Russian acronym for toroidal chamber with magnetic coils. Andrei Sakharov and Igor Tamm came up with the idea, and the 1958 T-1 is often counted as the first one built.

Which phenomenon makes water drops skitter across a very hot pan on a cushion of their own vapour?

The Leidenfrost effect lets a drop outlast one on a cooler pan, because above about 193 °C the cushion stops it touching the metal. It is named after German doctor Johann Leidenfrost.

Which icy Solar System bodies grow long glowing tails as sunlight turns their ice into gas?

Comets take their name from the Greek for long-haired star. Near the Sun their ice skips the liquid stage altogether, and the escaping gas and dust stream out as a tail.

Which name is given to the beads of water that settle on grass overnight as the ground cools?

Dew forms when grass and leaves cool by radiating away their heat, so moisture in the air condenses onto them. It favours thin, exposed things, which lose heat fastest.

Sound moves through air at about 343 metres per second, but almost 15 times faster through which material?

Iron carries sound at about 5,120 metres per second. As a rule, sound travels slowest in gases, faster in liquids and fastest in solids.

Fog, sea spray and wildfire smoke are all examples of which kind of fine mixture hanging in air?

An aerosol is any cloud of fine solid specks or liquid beads hanging in a gas. Spray cans borrowed the name because that is exactly what leaves the nozzle.

Very pure water can stay liquid down to about −48 °C as long as it lacks what?

A seed to grow around, such as a speck of dust or a first sliver of ice, is what freezing needs to get started. Water chilled past 0 °C without one is called supercooled.

Which Italian physicist invented the barometer, proving that the air above us has weight?

Evangelista Torricelli upended a tube of heavy liquid metal in a bowl and saw the column stay up, held there by the air outside pressing down on the bowl.

Which blue-grey metal is the densest stable element, about twice as dense as lead?

Osmium was discovered in 1803 and named for the smell of its oxide. It is so hard-wearing that its alloys are used to tip the nibs of fountain pens.

Which English pioneer of electricity also succeeded in turning gases such as chlorine into liquids?

Michael Faraday helped show that gases are simply the vapours of liquids with very low boiling points. He also discovered benzene and popularised the words electrode and ion.

Which exotic phase of matter, proposed by Frank Wilczek in 2012, keeps moving even at its lowest energy?

A time crystal is ordered in time as well as in space: its particles tick through the same cycle endlessly, and cannot wind down because they are already at their lowest energy.

Geckos climb glass using weak attractions between molecules that are named after which Dutch physicist?

Johannes van der Waals argued in his 1873 thesis that molecules attract one another, when many physicists still doubted molecules existed. A gecko's foot uses millions of tiny hairs to exploit the pull.

Which natural hazard forms when loose, waterlogged grains are suddenly shaken and start behaving like a liquid?

Quicksand lets a body sink only until it has pushed aside its own weight of the soupy mix, and then it floats. The trapped water is what robs the sand of its strength.