Billions of people eat food grown with fertiliser from a reaction first shown in 1909.
Fritz Haber showed how to make ammonia from nitrogen in the air and hydrogen; Carl Bosch scaled it up for industry. Ammonia is the base of most nitrogen fertilisers, including urea.
Why it matters: Pakistan's urea plants use this same process to feed its wheat and rice fields.
Haber–Bosch process — Fritz Haber and Carl Bosch (1909) Nobel Prize in Chemistry: Haber 1918, Bosch 1931
In a chemical reaction, nothing simply disappears.
By weighing substances carefully before and after reactions in sealed vessels, Lavoisier showed that the total mass stays the same. He also named oxygen and hydrogen.
Why it matters: Conservation of mass turned chemistry from guesswork into a science of measurement.
Traité élémentaire de chimie — Antoine Lavoisier (1789)
A chemist left gaps in his table — and the missing elements turned up later.
In 1869 Mendeleev arranged the known elements by atomic weight and properties, leaving gaps for undiscovered ones. Gallium (1875) and germanium (1886) later filled them as he predicted.
Why it matters: A strong theory does not just explain what we know; it predicts what we will find.
The Relation between the Properties and Atomic Weights of the Elements — Dmitri Mendeleev (1869) Presented to the Russian Chemical Society, March 1869