50 Fun Facts About Molecules

Which gas, a molecule of three oxygen atoms, forms a high layer that shields Earth from the Sun's ultraviolet rays?

Ozone takes its name from the Greek word for smell, after the sharp odour it leaves in the air following a lightning strike. The oxygen people breathe has only two atoms in each molecule.

Which gas that humans breathe out freezes into dry ice, the solid that makes stage fog without ever melting?

Carbon dioxide has no liquid stage at normal air pressure, so dry ice turns straight from a solid into a gas at about −78 °C. The name dry ice began life as a 1925 trademark.

What does water do as it freezes, unlike most liquids, because its molecules lock into an open six-sided pattern?

It expands by about 9%, which makes ice less dense than liquid water, so ice floats. That is why ponds freeze from the top down instead of from the bottom up.

Which molecule do coffee and tea plants make as a natural pesticide that can paralyse and kill feeding insects?

Caffeine is the world's most widely consumed psychoactive drug. In flower nectar a small dose seems to sharpen a honey bee's memory of the reward, so the bee keeps coming back.

Which cleaning product, made in Babylon around 2800 BC, has molecules with a water-loving head and a grease-loving tail?

Soap molecules wrap specks of grease in tiny spheres called micelles, tails pointing in and heads pointing out. Plain water can then rinse the trapped dirt away.

Which American founding father calmed a London pond with a teaspoon of oil, a film later shown to be one molecule thick?

Benjamin Franklin watched the oil smooth the waves across about half an acre of the pond at Clapham Common. Over a century later Lord Rayleigh measured how thin such an oil film is.

Which gas, one carbon atom bonded to four hydrogens, is the main ingredient of natural gas and is belched out by cows?

Methane has no smell of its own, so a strong-smelling additive goes into household gas to make leaks noticeable. Cattle belch most of theirs out as gut microbes ferment their food.

Which gas, whose paired atoms are locked together by a very strong triple bond, makes up about 78% of Earth's air?

Nitrogen molecules are so hard to split that most living things cannot use the gas straight from the air. Lightning and certain bacteria break the bond and turn it into plant food.

Which kitchen staple, a crystal lattice of sodium and chloride ions, contains no separate molecules at all?

Table salt has six neighbours of the opposite charge around every ion, so no pair belongs together as one molecule. Dissolving it in water pulls the lattice apart ion by ion.

Which molecule makes chilli peppers burn by tricking the nerve sensors that normally detect scalding heat?

Capsaicin puts off mammals, whose teeth crush the seeds, but birds cannot feel it at all. Birds swallow the seeds whole and scatter them, which suits the plant nicely.

Which everyday measurement, bottoming out at absolute zero, tracks how fast a substance's molecules are jiggling?

Temperature reflects the average energy of motion of the particles in a substance. Robert Hooke argued for the link in a lecture in 1681, long before anyone could prove that molecules exist.

Which property of water, caused by its molecules clinging to one another, lets water striders walk across a pond?

Surface tension can hold up things denser than water, such as a steel razor blade laid flat. The same inward pull rounds falling water into droplets.

Which process, the drift of molecules from crowded places to emptier ones, moves oxygen from the lungs into the blood?

Diffusion is passive, so the body spends no energy on it. Randomly jostling molecules simply spread from where they are crowded to where they are scarce.

Which Italian scientist, trained as a lawyer, gives his name to the number of molecules in one mole of a substance?

Amedeo Avogadro never knew the number that carries his name. The French physicist Jean Perrin coined the term in 1909, more than fifty years after the Italian's death.

Which family of elements, including neon and argon, exists as lone atoms because it almost never bonds into molecules?

Noble gases have a full outer shell of electrons, which leaves them little reason to react. Argon was even named after the Greek word for lazy.

Which simple sugar do plants build in photosynthesis and animals carry in the blood as fuel for their cells?

Glucose is the most abundant simple sugar in nature. Plants also chain thousands of its units together to make cellulose, the tough material of their cell walls.

Which sugar in milk can most of the world's adults no longer digest fully, for lack of an enzyme?

Lactose takes its name from the Latin word for milk. Babies make the enzyme that splits it, but in most people the supply fades after childhood, except among peoples with a long history of herding.

Which painkiller, first sold worldwide by the German firm Bayer, is a lab-made relative of a remedy from willow bark?

Aspirin began as Bayer's own brand name, and the company later lost the trademark in many countries. Willow remedies appear on clay tablets from ancient Sumer.

Which molecule, water with one extra oxygen atom, bleaches hair and helps bombardier beetles fire a boiling spray?

Hydrogen peroxide slowly breaks down in light, which is why pharmacies sell it in brown bottles. All it leaves behind is water and oxygen.

Which type of chemical bond, the kind holding a water molecule together, forms when atoms share pairs of electrons?

Covalent bonds are a partnership: the 'co' in the name means jointly, as in co-operate. The American chemist Irving Langmuir coined the term in 1919.

Which word describes a substance like water, whose molecules contain more than one element, unlike oxygen gas?

A compound can behave nothing like its ingredients. Water puts out fires, yet it is built from hydrogen, which burns, and oxygen, which feeds flames.

Which word, built on the Greek for two, describes the molecules of oxygen and hydrogen gas, each a bonded pair?

Diatomic hydrogen is the lightest molecule of all, so light that it escapes Earth's atmosphere faster than heavier gases. Bromine forms the same kind of pairs as a liquid.

Which word describes giant molecules, such as rubber, nylon and DNA, built from long chains of small repeating units?

Polymer comes from the Greek for many parts. Nature got there long before the plastics industry: silk, wool and the cellulose in wood are all long chain molecules.

Which term, from the Greek for equal parts, describes molecules with the same formula but differently arranged atoms?

Isomers can behave very differently despite their identical ingredients. One form of the molecule carvone smells of spearmint, while its mirror-image twin gives caraway seeds their smell.

Which word describes a molecule such as water, with a slightly positive end and a slightly negative end?

Polar molecules try to line up with an electric field, and a microwave oven exploits that. Its waves keep the water in food spinning, and the motion turns into heat.

Which shape does a water molecule have, because two unshared pairs of electrons push its hydrogen atoms to one side?

Bent at about 104.5 degrees, a water molecule ends up slightly negative on its oxygen side and slightly positive on the other. That lopsided charge makes water molecules cling together.

Which family of molecules, the main ingredients of petrol and candle wax, contains only two kinds of atom?

Hydrocarbons contain nothing but hydrogen and carbon, yet they range from lighter gas to petrol to solid wax. Crude oil, natural gas and coal are their main natural sources.

Which poisonous gas with no smell or colour, made when fuel burns without enough air, do household alarms detect?

Carbon monoxide grips the oxygen-carrying protein in blood about 240 times more strongly than oxygen does. Even a little in the air crowds out the oxygen the body needs.

Which ring-shaped molecule's structure did August Kekulé say came to him in a daydream of a snake biting its tail?

Benzene is a flat hexagon of six carbon atoms, each holding one hydrogen. Michael Faraday first isolated it in 1825 from the oily residue left by making gas for lamps.

Which American chemist won a Nobel Prize for explaining the chemical bond and a second for campaigning for peace?

Linus Pauling is the only person to have won two unshared Nobel Prizes. The peace award was announced on the very day a treaty limiting nuclear weapons tests came into force.

Which sharp-smelling gas, named after the Egyptian god Amun, is made in vast amounts to produce farm fertiliser?

Ammonia owes its name to a mineral gathered near a temple of Amun in Roman North Africa. About 70% of what factories make goes into fertiliser.

Which alcohol molecule do yeasts make when they ferment sugar, the same one burned as car fuel across Brazil?

Ethanol is the oldest known sedative, given to patients before surgery in ancient Mesopotamia. It also turns up naturally in overripe fruit and in icy dust clouds between the stars.

Which acid, probably the first that humans ever made in bulk, gives vinegar its sour taste and sharp smell?

Acetic acid forms by itself when beer or wine is left open to the air, because the bacteria that make it live everywhere.

Which small molecules, the first of them found in asparagus, link in long chains to build every protein?

Amino acids come in more than 500 natural kinds, yet living things build their proteins from a set of only about twenty. The asparagus one, isolated in 1806, is called asparagine.

Which small gas molecule do ripening fruits give off, a plant hormone that farmers also use to ripen their crops?

Ethylene is also made in greater tonnage than any other carbon-based chemical. Factories string much of it into polythene, the most commonly produced plastic.

Which flavour molecule, the main taste of a climbing orchid's cured seed pods, is now mostly made in factories?

Vanillin from real pods is scarce and costly, so the synthetic kind is used far more often. In the 1930s factories began making it from lignin, a waste product of pulping wood for paper.

Which English chemist, who described his own colour blindness, said atoms join in fixed whole-number ratios?

John Dalton's preserved eyeball was tested in 1995 and confirmed the red-green colour blindness he had described in himself. Several languages still call the condition Daltonism.

Which American architect, famous for geodesic domes, gives his name to a football-shaped molecule of 60 carbon atoms?

Buckminster Fuller never saw the molecule that carries his name: he died in 1983, two years before chemists identified it. Its cage of 20 hexagons and 12 pentagons matches a classic football.

Which non-stick pan coating was found by accident inside a DuPont gas cylinder as a slippery white wax?

Teflon is a long chain of carbon atoms sheathed in fluorine, joined by bonds so strong that almost nothing reacts with it or sticks to it. An early job was sealing pipes in the Manhattan Project.

Which simple acid, named after the Latin word for ant, is also found in the stinging hairs of nettles?

Formic acid was first isolated in 1671 by the English naturalist John Ray, who distilled it from large numbers of ants. Wood ants can spray it at prey or at attackers on the nest.

Which word describes a molecule that, like a human hand, cannot be laid exactly over its own mirror image?

Chiral comes from the Greek word for hand. Louis Pasteur revealed the effect by picking apart left-handed and right-handed crystals of the same substance by hand.

Which waste molecule of the body did Friedrich Wöhler make from lifeless chemicals, a famous first for chemistry?

Urea had only ever come from living bodies until then. Wöhler boasted in a letter that he could now make it without kidneys, or indeed any animal, be it man or dog.

Which molecule, made by soil bacteria, gives rain on dry ground its earthy smell and beetroot its earthy taste?

Geosmin is something the human nose is astonishingly tuned to, picking it up at a few parts per trillion. When bacteria in a reservoir die off, it can make tap water taste musty.

Which giant muscle protein, a molecular spring, has a full chemical name that runs to 189,819 letters?

Titin is named after the Titans, the giants of Greek myth. Dictionary makers treat its full name as a chemical formula spelled out in words, so it never counts as the longest English word.

Which molecule, thought to be the very first to form after the Big Bang, was finally detected in space in 2019?

Helium hydride was first made in a laboratory in 1925, but it took an airborne telescope to spot it in a distant nebula. It is also rated the strongest known acid.

Which term describes different forms of one element, such as diamond and graphite, built from the same atoms?

Allotropes of one element can be worlds apart. Diamond is transparent and extremely hard, while graphite, built from the very same carbon atoms, is black and soft enough to write with.

Which American chemist, who drew electrons as dots around atoms, had 41 Nobel Prize nominations but never won?

Gilbert Lewis also coined the word photon for a particle of light, in 1926. His picture of atoms bonding through shared pairs of electrons still shapes how chemists draw molecules.

Which British chemist, a former tutor of Margaret Thatcher, won a Nobel Prize for mapping molecules with X-rays?

Dorothy Hodgkin spent 35 years working out the structure of insulin, finishing in 1969. Thatcher, once her chemistry student, later hung Hodgkin's portrait in Downing Street.

Which jittery movement of specks in water, explained by Albert Einstein, convinced scientists that molecules exist?

Brownian motion is named after Robert Brown, a Scottish botanist who watched pollen particles jiggle under his microscope in 1827. Its cause stayed a mystery for almost 80 years.

Which bitter molecule in cocoa makes chocolate dangerous for dogs, whose bodies break it down far too slowly?

Theobromine contains no bromine at all. The name comes from Theobroma, the cacao tree's scientific name, which means food of the gods.