Chemistry
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This chemistry trivia quiz has 178 free questions with answers and starts with the fundamentals (atoms, the periodic table, bonding, acids and bases, redox, states of matter) and works up to organic chemistry: alkanes and their isomers, alkenes and alkynes, functional groups from alcohols to esters, Kekulé's benzene ring, Markovnikov's rule, Grignard reagents and the Diels-Alder reaction, plus the people who built the field, from Wöhler and Liebig to Perkin and Pasteur. Questions range from easy ones any science student can handle to hard ones aimed at people who have actually sat an organic chemistry exam. Every question shows its difficulty, so you can pull an easy round for a classroom or a hard round for a lab-group quiz night. Every answer has been checked against a primary reference and each question carries its citation.
30 of 178 questions with answers and explanations. Play the quiz
Q 01Which chemist created the first widely accepted periodic table?
Dmitri Mendeleev
Dmitri Mendeleev left gaps in his table for elements nobody had found and forecast their properties; three of them were discovered within twenty years, closely matching his predictions.
Q 02Beyond solid, liquid and gas, what is usually counted as the fourth state of matter, the stuff of stars and lightning?
Plasma
Plasma forms when a gas is heated or electrified until electrons break free of its atoms, which is why it conducts electricity and glows, as in a neon sign.
Q 03What type of chemical reaction absorbs heat energy from its surroundings?
Endothermic
Endothermic changes soak up heat from their surroundings, which is how an instant cold pack works: squeezing it lets ammonium nitrate dissolve in water, and the pack turns cold.
Q 04Dry ice is the frozen form of which gas?
Carbon dioxide
Carbon dioxide has no liquid state at normal pressure, so dry ice at −78.5 °C turns straight into gas, keeping food frozen without leaving a puddle.
Q 05What subatomic particle found in the nucleus of an atom carries a positive electric charge?
Proton
Proton: the number of protons fixes which element an atom is, so no chemical reaction could turn lead into gold as the alchemists hoped; that takes a nuclear change.
Q 06What is the chemical symbol for the element gold?
Au
Au is short for aurum, gold's Latin name. Gold is so unreactive that it is usually found in nature as the pure metal, in nuggets and grains, and not locked up in a compound.
Q 07What is the common name for sodium chloride?
Table salt
Table salt joins two hazards: sodium, a soft metal that reacts violently with water, and chlorine, a poisonous gas. Bonded together, they are safe to sprinkle on dinner.
Q 08Which acid does the human stomach produce to help digest food?
Hydrochloric acid
Hydrochloric acid would damage the stomach itself, so the lining shields itself with mucus and bicarbonate; heartburn is what happens when the acid escapes up into the gullet.
Q 09What is the approximate pH of pure water at 25°C?
7
Pure water at 25 °C has a pH of 7: H⁺ and OH⁻ are both 10⁻⁷ mol/L, so it is neutral. Heated above 25 °C, the neutral point drifts below 7.
Q 10What type of chemical bond has atoms sharing electron pairs, the kind that holds a water molecule together?
Covalent bond
A Covalent bond shares electrons; an ionic bond transfers them, a metallic bond pools them, and a hydrogen bond is just an attraction between molecules, the one that makes ice float.
Q 11Which functional group has a carbon double-bonded to oxygen and bonded to a hydrogen and an R group?
Aldehyde
Aldehyde: when the body breaks down the ethanol in drinks, the first product is acetaldehyde, a toxic member of this family that contributes to hangovers.
Q 12In a redox reaction, what term describes the loss of electrons by a chemical species?
Oxidation
Oxidation once meant only combining with oxygen; chemists later widened it to any loss of electrons, remembered as OIL RIG: oxidation is loss, reduction is gain.
Q 13Which reaction type has an acid and a base forming a salt and water?
Neutralization
Neutralization is how milk of magnesia settles heartburn: its magnesium hydroxide, a base, reacts with excess stomach acid to leave a salt and water.
Q 21A solution with a pH of 2 is considered what type of substance?
Acidic
Acidic, and strongly so: the pH scale is logarithmic, so each step down means ten times more acidity, making pH 2 a thousand times more acidic than pH 5.
Q 22Who is credited with the discovery of the electron?
J.J. Thomson
J.J. Thomson showed in 1897 that cathode rays are particles far smaller than atoms; forty years on, his son George shared a Nobel Prize for proving that electrons also behave as waves.
Q 23What is the primary chemical compound found in rust?
Iron oxide
Iron oxide in the form of rust is flaky and falls away, exposing fresh metal to corrode, whereas many other metals grow a tight oxide film that seals the surface.
Q 14What is the typical oxidation number of an uncombined element?
0
0 is the oxidation number of any free element: in oxygen gas or a lump of iron every atom is bonded only to its own kind, so none has gained or lost electrons.
Q 15Which transition metal forms the outer skin of the Statue of Liberty?
Copper
Copper, like most transition metals, forms strongly coloured compounds: the statue was as brown as a penny when new, and its skin weathered to a green patina that protects the metal beneath.
Q 16Which functional group contains a carbonyl group bonded to two other carbon atoms?
Ketone
Ketone: the simplest is acetone, the solvent in nail-polish remover, and the body makes ketones of its own when it burns fat for fuel, the 'keto' in a ketogenic diet.
Q 17An organic compound whose molecule carries a –COOH group belongs to which class?
Carboxylic acid
A carboxylic acid is what makes vinegar and lemons sour: acetic acid and citric acid both carry the –COOH group, which gives up its hydrogen as an ion in water.
Q 18Which functional group, with the structure R-COO-R', gives many fruits their sweet smells?
Ester
Ester molecules give bananas, pineapples and pears their scent: isoamyl acetate is sold as 'banana oil', and the flavour industry uses esters to imitate fruit.
Q 19What name is given to a metal blended with other elements, as bronze and steel are?
Alloy
Alloy: blending changes how a metal behaves, so bronze is harder than either of the metals melted into it, and a little carbon turns iron into much stronger steel.
Q 20Which gas makes up about 78% of Earth's atmosphere by volume?
Nitrogen
Nitrogen fills most of the air, yet plants and animals cannot use it as a gas: its triple bond is so strong that life depends on certain bacteria, and lightning, to 'fix' it.
Q 24Which group of elements, with full outer electron shells, sits in the periodic table's last column and barely reacts with anything?
Noble Gases
Noble Gases had no place in the first periodic tables because none had yet been isolated; once the first was isolated in the 1890s, a whole new column was added to hold the family.
Q 25Which gas gives rotten eggs their smell?
Hydrogen sulfide
Hydrogen sulfide is smelled at the faintest trace, yet at high concentrations it deadens the sense of smell within minutes, so the warning vanishes just as the gas becomes dangerous.
Q 26What is the name for a solid changing directly into a gas without first becoming a liquid?
Sublimation
Sublimation is why snow can shrink on dry, sub-zero days without ever melting, and it is the trick behind freeze-dried food: the ice is drawn off as vapour under low pressure.
Q 27Atoms of the same element with different numbers of neutrons, such as carbon-12 and carbon-14, are called what?
Isotopes
Isotopes of an element share one square of the periodic table, and that is what the name says: it was coined in 1913 from the Greek for 'same place'.
Q 28What term describes a substance that speeds up a chemical reaction without being consumed?
Catalyst
A catalyst works by opening an easier route for the reaction; the platinum in a car's catalytic converter turns toxic exhaust gases into less harmful ones without being used up.
Q 29What type of chemical reaction releases energy, often as heat or light?
Exothermic
Exothermic reactions give out more energy than it takes to start them: burning is the classic case, and the iron powder in a disposable hand warmer heats up as it reacts with air.
Q 30What type of hybridization does the carbon atom exhibit in a methane (CH₄) molecule?
sp³
sp³ means one s and three p orbitals blend into four identical ones pointing to the corners of a tetrahedron, so methane is not the flat cross it looks on paper: its bonds sit about 109.5° apart.