Celsius Trivia
0Loading crowd target
0Loading crowd target
6correct to beat the crowd
49 free Celsius trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Celsius trivia begins with a surprise: the Swedish astronomer who proposed the scale in 1742 put boiling water at 0 and freezing at 100, and it took a French physicist and Carl Linnaeus to turn it the right way up. The name 'centigrade' survived until 1948, when it was dropped partly because it also meant a hundredth of a right angle in French. This quiz covers Anders Celsius himself (Uppsala, the aurora, the Lapland expedition), the history of the scale, the difference between a temperature and an interval, why the boiling point of water is no longer exactly 100 °C, the kelvin and absolute zero at −273.15 °C, Daniel Fahrenheit's brine and body-heat fixed points, the −40 crossover, the Réaumur and Rankine scales, the triple point of water, the 2019 Boltzmann-constant redefinition, and the handful of countries where Fahrenheit still rules the weather forecast. Easy questions suit anyone who has read a thermometer; the expert tier is for metrologists. Every answer was checked against Wikipedia's articles on the scales and their inventors, and the supporting sentence is attached to each question.
30 of 49 questions with answers and explanations. Play the quiz
Q 01Which cold-weather emergency sets in when the body's core temperature falls below 35 °C?
Hypothermia
Hypothermia. Below 35 °C the body is losing heat faster than it can make it, and because the cold also dulls thinking, victims often fail to realise they need help.
Q 02In Anders Celsius's original 1742 scale, what temperature was 0 degrees?
The boiling point of water
The boiling point of water. Celsius put freezing at 100, so his thermometer's numbers climbed as the weather got colder; within a few years others had flipped it to the form used today.
Q 03Which Italian scientist is credited with inventing the thermoscope, a forerunner of the thermometer, around 1600?
Galileo Galilei
Galileo Galilei. His glass bulb and tube showed a liquid rising and falling with the temperature, but with no scale it could only show a change, never measure one.
Q 04Which 1740s naturalist had a modern-style Celsius thermometer built for his greenhouses?
Carl Linnaeus
Carl Linnaeus. He is often named as the man who gave the scale its modern form, but several scientists and instrument makers adopted it at about the same time, and no single person can take the credit.
Q 05What was the Celsius scale commonly called in English before 1948?
Centigrade
Centigrade, meaning a hundred steps. It was renamed after Anders Celsius in 1948, partly because in France the word centigrade was already in use for a unit of angle.
Q 06What heats its surroundings to about 30,000 °C, roughly five times hotter than the Sun's surface?
A lightning bolt
A lightning bolt. The flash heats the gases in its path so suddenly that they burst outward as a shock wave, and that is the sound we hear as thunder.
Q 07Which planet has the Solar System's hottest surface, about 465 °C, though another lies closer to the Sun?
Venus
Venus. Its thick carbon-dioxide atmosphere traps heat in a runaway greenhouse effect, leaving the surface hot enough to melt lead.
Q 08What is absolute zero on the Celsius scale?
−273.15 °C
−273.15 °C. Nothing can be colder, because at absolute zero particles have as little motion as nature allows, which is why the Kelvin scale starts its count there.
Q 09Which element has the lowest boiling point of all, about −269 °C?
Helium
Helium. Even at that temperature it only turns liquid, and at ordinary pressure it will not freeze solid however far it is chilled.
Q 10Since 1967, the degree Celsius has been the only SI unit whose full name has what feature?
An uppercase letter
An uppercase letter. SI unit names are written in lower case even when they honour a person, like newton and watt, and 'degrees Kelvin' fell into line in 1967 by becoming plain 'kelvin'.
Q 11Under SI rules '30 °C' takes a space; the only unit symbols allowed to touch their number appear in which of these?
A ship's latitude
A ship's latitude. The SI treats °C like any other unit symbol and sets it off with a space, but the degree, minute and second signs for angles sit directly against the number, as in 45°.
Q 12A 1975 US law backed moving to metric units, Celsius included; why did Fahrenheit survive?
The switch was voluntary
The switch was voluntary. The Metric Conversion Act created a board to coordinate the change but gave nobody the power to require it, and the board itself was abolished in 1982.
Q 13At what temperature do the Celsius and Fahrenheit scales give the same number?
−40
Q 21From 1954 to 2019, the kelvin and the degree Celsius were defined by which fixed point of water?
Its triple point
Its triple point. Ice, liquid water and vapour coexist at only one temperature, and the scale's zero was set exactly a hundredth of a degree below it; a physical constant took over in 2019.
Q 22The 2019 revision of the SI defined the base unit of temperature by fixing which physicist's constant?
Boltzmann's
Boltzmann's. His constant ties temperature to the energy of moving particles, so since 2019 the kelvin has rested on a fixed number rather than on any property of water.
Q 23At about 4 °C, liquid water reaches its maximum what, which is why lakes freeze from the top down?
Density
−40. A Fahrenheit degree is only five-ninths the size of a Celsius degree, so the two scales close in on each other as it gets colder and meet exactly once, at minus forty.
Q 14By his own 1724 account, what did Daniel Fahrenheit use to set the zero of his scale?
An ice-and-salt mixture
An ice-and-salt mixture. Such a brine settles by itself at one steady chill, about −18 °C, so he could recreate his zero in a workshop without waiting for a cold day.
Q 15Fahrenheit originally fixed 96 degrees on his scale as the temperature of what?
The human body
The human body. When the scale was later re-pinned to water's freezing and boiling points at 32 and 212, normal body temperature slid from 96 to the familiar 98.6.
Q 16Which London body published Daniel Fahrenheit's 1724 thermometer papers?
Royal Society
Royal Society. Its Philosophical Transactions printed five papers by him in a single year, giving the benchmarks of his scale, including the 32 and 212 still used for water.
Q 17Daniel Fahrenheit is credited with making the first successful thermometers filled with what?
Mercury
Mercury. It proved an excellent liquid for showing changes in temperature, and his thermometers agreed so closely that observers in different places could at last compare readings.
Q 18Which Copenhagen astronomer's temperature scale did Daniel Fahrenheit adapt into his own after visiting him?
Ole Rømer
Ole Rømer. After the visit, Fahrenheit split each degree of Rømer's scale into four, which is how his own finer scale began.
Q 19Lord Kelvin, namesake of the absolute temperature scale, took his title from a river in which city?
Glasgow
Glasgow. William Thomson was a professor at its university from 1846, and when he was made a baron in 1892 he chose the name of the River Kelvin, which runs through the university grounds.
Q 20Which process, devised in the 1860s to keep wine from spoiling, now heats milk to about 72 °C?
Pasteurisation
Pasteurisation. Louis Pasteur found that gentle heating killed the microbes that soured wine, and the method was extended to milk only later.
Density. Water colder than 4 °C is lighter and stays on top, so ice forms as a lid over the lake; if the coldest water sank instead, lakes would freeze from the bottom up.
Q 24Calling 20 °C 'twice as hot' as 10 °C is a mistake because the Celsius scale lacks what?
A true zero
A true zero. Zero Celsius is only where water freezes, so ratios mean nothing on it; counted from absolute zero in kelvins, 20 °C is just 3.5% hotter than 10 °C.
Q 25Instead of melting, dry ice undergoes which change of state at about −78 °C?
Sublimation
Sublimation. Dry ice is frozen carbon dioxide, which has no liquid state at normal atmospheric pressure, so instead of leaving a puddle the block turns straight into a cold gas.
Q 26Which law of thermodynamics implies that absolute zero cannot be reached in a finite number of steps?
The third
The third law of thermodynamics. It means cooling anything all the way to absolute zero would take an infinite number of steps, though laboratories have chilled atoms to within billionths of a degree of it.
Q 27Around 1700, Guillaume Amontons glimpsed the idea of absolute zero while studying the 'spring' of what?
Air
Air. He saw that cooled air pushes back less, and reasoned that at some low enough temperature it would lose its spring altogether, a limit to cold proposed almost 150 years before Kelvin's scale.
Q 28Which metal has the highest melting point of all, about 3,400 °C?
Tungsten
Tungsten. That is why light-bulb filaments were made of it: they can glow white-hot without melting, yet the pure metal is soft enough to be cut with a hacksaw.
Q 29Which metal melts at just under 30 °C, so a solid lump of it turns liquid in a warm hand?
Gallium
Gallium. Mendeleev predicted the metal and its low melting point from a gap in his periodic table, and its discovery in 1875 was an early triumph for the table.
Q 30At which university was Anders Celsius professor of astronomy from 1730 until his death?
Uppsala
Uppsala. Fame from an Arctic expedition helped him persuade the Swedish authorities to pay for a modern observatory there, which opened in 1741.