Water is science-friendly as well as life-friendly. Michael Denton covers the life-friendly aspects in his book The Wonder of Water. Jay Richards and I cover the science-friendly aspects in The Privileged Planet, whose new expanded and rewritten edition is out now for our book’s 20th anniversary.

The Liquid Foundation of Chemistry

Water has been crucial in the transition from alchemy to the science of chemistry. Its unique properties and ubiquity have made it central to countless experiments and discoveries that shaped our understanding of matter and chemical reactions.

According to the ancient Greeks, water was one of the four basic elements of the Earth. This belief persisted for centuries and laid the foundation for alchemy, a proto-scientific practice aimed at transforming matter, particularly turning base metals into gold and seeking the elixir of life. Even until the 18th century, scientists still thought water was a basic substance, an element. Water was the most important substance in the alchemist’s laboratory, serving as the universal medium for studying reactions. 

Sparks of Revolution: Splitting the “Element”

In 1783 Antoine-Laurent Lavoisier, today considered the founder of the science of chemistry, reacted hydrogen and oxygen gases in a chamber with a spark and produced pure water. In another experiment, this time involving heated iron and water, he showed that water is composed of hydrogen and oxygen. Sadly, “enlightened” French revolutionaries executed Lavoisier in 1794. A few years later, motivated by Alessandro Volta’s invention of the electric battery, British scientists Anthony Carlisle and William Nicholson first passed an electric current from a battery through water (a process called electrolysis). As the water disappeared, two gases appeared. One of them was hydrogen, and the other oxygen. This was an elegant confirmation of Lavoisier’s earlier results.

These experiments showed that water, long considered an elemental substance, was actually a compound composed of simpler elements. As a result, water was no longer elemental. The distinction between elements, which are composed of a single type of atom, and compounds, which are combinations of elements, became a cornerstone of chemical science. Lavoisier was the first to discover this truth.

Popular nature writer Rutherford Platt commented on the significance of this discovery: 

As a milestone in the progress of probing nature’s secrets, the splitting of a molecule of water into two H’s and one O is comparable to the splitting of the atom in our time. Prior to this, scientists had no clues to the composition of water . . . and H₂O led to the recognition of the elements and modern chemistry.

Water: The Wonder of Life (Englewood Cliffs, N.J.: Prentice-Hall, 1971), p. 16

When Water Fell Apart, Chemistry Came Together

The decomposition of water into hydrogen and oxygen had far-reaching implications for chemistry. It paved the way for the development of atomic theory, as scientists sought to explain how and why elements combined to form compounds.

The water decomposition experiments also laid the foundation for stoichiometry, the quantitative study of reactants and products in chemical reactions. The fixed 2:1 ratio of hydrogen to oxygen in water became a model for understanding chemical proportions and reactions. 

Electrolysis proved to be a fruitful method for isolating new elements. Many were discovered in the two decades following the electrolysis experiment with water. The elements were somehow electrical in nature. Chemists were beginning to learn about how electrical charges were involved in chemical reactions and introduced the concept of ions. In 1834 Michael Faraday proposed his laws of electrolysis, relating the current passing through an electrolyte liquid and the amount of material deposited or consumed at an electrode. Electrolysis would become very important for large-scale industrial processes starting later that century.

H₂O: A Chemical Marvel

Water is the most abundant compound in the universe, made of the most abundant element and the third. It is also one of the simplest compounds. No doubt its simplicity was a factor in the early successes of Lavoisier, Carlisle, and Nicholson. If some more complex liquid replaced water as the medium of life, such as formamide (HCONH₂), it would have been much more difficult to fully separate the constituent elements. 

Benjamin Wiker and Jonathan Witt nicely summarize these features of water:

What is quite strange, quite unexpected, is that while water is not itself an element, it is one of the simplest of compounds — about the shortest step possible from elements to a compound. That simplicity made it relatively easy to take apart, to recognize the two parts as elemental, and to put it back together again — an enormous intellectual leap.

A Meaningful World, p. 128

It was probably also helpful to early chemistry experiments that Earth’s atmosphere is relatively simple in its composition; 99 percent of its molecules are made of two just two elements, oxygen and nitrogen. Most of the remaining 1 percent is inert argon, and nitrogen is mostly unreactive. No doubt that had something to do with Lavoisier’s discovery of oxygen as an element (and independently, Joseph Priestley).

Water’s molecular structure gives it several unique properties that have been crucial for chemical experimentation and understanding. Its polar nature, resulting from the uneven distribution of electrons between oxygen and hydrogen atoms, allows it to dissolve a wide range of substances. Its polarity also contributes to the unusually high boiling and melting points for a molecule of its size, making it stable in liquid form at room temperature — a critical factor for many chemical processes — and critical for life on Earth.

Perhaps most importantly, water’s status as a universal solvent has made it invaluable in chemistry. Its ability to dissolve more substances than any other liquid has allowed chemists to study a vast array of reactions in solution. 

The Universal Stage for Molecular Drama

Water’s role as a reaction medium cannot be overstated. Its ability to facilitate the dissolution of substances, particularly ionic compounds, has been crucial for studying chemical reactions. The concept of ions originated when salt was dissolved in water. In aqueous solutions, ions are free to move and interact, enabling a wide range of ionic reactions that would be impossible in other media.

In the late 19th century, Arrhenius introduced his theory of acids and bases from his theory of ions. Acids and bases are defined in terms of what happens when a substance dissolves in water. The behavior of acids and bases in water helped scientists classify materials and understand their properties, laying the groundwork for more advanced chemical concepts.

Moreover, water often serves as more than just a passive medium. It can act as a catalyst, speeding up certain reactions without being consumed. A common example is iron rusting. In many biochemical processes, water is an active participant, serving as a reactant or product in hydrolysis and condensation reactions.

Weird and Wonderful Water

Why would the most common compound in the universe be the most anomalous, one of the simplest, and essential for life? Did I mention how water’s transparency to light is highest close to the peak of the sun’s spectrum and also to the maximum sensitivity of human vision? Common, anomalous, and simple: that’s an interesting combination. It’s also, frankly, weird.