Unbelievable: amateur chemist decomposes water!

It is a sensation for science: water can be split into two parts. The French banker and amateur chemist Antoine Laurent de Lavoisier (born 26 August 1743) proved this in an amazing experiment.

A year before his experiment, Lavoisier had already heard from England that water could be split into two gases. The British nobleman Henry Cavendish (born 17 October 1731) had discovered hydrogen in his experiments. Lavoisier copied Cavendish’s experiments and again split water into hydrogen and oxygen. After recovering water from the two gases, he declared to the astonished public: “The combustion of the two kinds of air and their transformation into water, part by part by weight, leaves little doubt that this substance, hitherto considered as an element, is a compound substance.”

A groundbreaking insight! To prove it, Lavoisier had passed water vapour through a glowing iron pipe to obtain hydrogen and oxygen. The oxygen reacted with the glowing iron to form iron oxide. In turn, pure hydrogen collected in a pig’s bladder!

Comment: Aristotle was wrong here!

Fire, water, earth, air – according to the teachings of the ancient Greeks, every substance is composed of these four elements. Until recently, we believed that water was an element that could not be divided. But with his experiment, Antoine Laurent de Lavoisier brought down the beautiful theory of antiquity: water can indeed be divided, namely into its two components hydrogen and oxygen. The four-element theory is therefore old news! And the experiment of the Frenchman Lavoisier means nothing less than a revolution for science!

What water can do

No matter whether we drink tap water, jump into a lake or are surprised by a downpour – we constantly come into contact with water. And not only that: we ourselves are made of water, in fact about two-thirds of it. Without question, water is part of our everyday life. But what seems quite normal to us has all kinds of peculiarities. And water owes these above all to its structure.

Everything that exists on this earth is made up of tiny building blocks, the atoms. This is also the case with pure water: it is a compound of two hydrogen atoms and one oxygen atom. These combine to form a water molecule, or H2O for short. The individual water molecules are only loosely connected to each other.

This loose cohesion ensures that the bond between the molecules breaks down at high temperatures: the water evaporates. If, on the other hand, it cools down strongly, the molecules arrange themselves into a solid, regular lattice, the ice. The special thing about it: In solid form, water has a larger volume than in liquid form.

The arrangement of the water molecules provides yet another property: the surface tension of the water. Because of this tension, water spiders and water striders can walk effortlessly on a pond. But water can do even more: it is able to dissolve substances. Small grains of salt or sugar dissolve completely in water. Sea water, for example, contains large amounts of salt that we can taste but not see.

The fact that lemons ripen on the island of Mainau on Lake Constance is thanks to another ability of water: it can store heat. Lakes or seas heat up in summer and retain the heat for a long time. That is why temperatures fluctuate less on the coast than inland. Far from the coast, the temperature differences between day and night and between summer and winter are much greater than near the sea.

Water as a quick-change artist

Water is known to be liquid. However, this is not always true. In nature, water occurs in three states: As liquid water, as gaseous water vapour or as solid ice. Depending on external conditions, it changes from one state to the other.

The state of water depends on its pressure and temperature. If liquid water exceeds the boiling point, it evaporates and floats in the air as gaseous water vapour. Water also changes into a gaseous state when it evaporates at room temperature. However, this happens more slowly than during evaporation. If, on the other hand, the temperature drops below 0° Celsius, the water freezes into ice. As soon as water changes its state between liquid, gaseous or frozen, it changes its properties.

The special thing about water is that it has its greatest density at 4° Celsius and takes up very little space. When it freezes into solid ice, it expands and increases its volume. At the same time, its density decreases. That is why ice is lighter than water with the same volume. This is why icebergs can float in the sea. For the same reason, a lake freezes over from above and not from below in winter. This is a good thing, because otherwise we would not be able to skate until the lake was completely frozen from the bottom to the surface.

So water expands when it freezes. If you prevent it from doing so, it exerts enormous pressure. Anyone who has ever left a bottle of water outside in the freezing cold knows the consequences: After some time, the bottle bursts and the ice spills out. Ice can also crack stone in this way. This happens when water flows into cracks in the rock, freezes there and pushes outwards due to the expansion. When this force causes pieces of the stone to break off, it is called frost blasting. Anyone who has ever driven into a pothole knows the consequences. Here, the constant alternation of wetness and frost has taken its toll on the asphalt.

The blue planet

Seen from space, the earth’s sphere appears a strong blue. This is because almost three quarters of the earth is covered with water. Although water is transparent in small quantities, from a certain depth it takes on an increasingly strong blue shimmer. Because we see the mighty oceans as blue, the Earth is also called “the blue planet”. The term is particularly true south of the equator. This is because the southern hemisphere is almost completely covered by sea, because a large part of the continents have migrated northwards due to plate movement.

The blue planet

Seen from space, the earth’s sphere appears a strong blue. This is because almost three quarters of the earth is covered with water. Although water is transparent in small quantities, from a certain depth it takes on an increasingly strong blue shimmer. Because we see the mighty oceans as blue, the Earth is also called “the blue planet”. The term is particularly true south of the equator. This is because the southern hemisphere is almost completely covered by sea, because a large part of the continents have migrated northwards due to plate movement.

The vast oceans contain almost all the water on earth. A lot of salt is dissolved in seawater, which is why it is not suitable as drinking water. What little fresh water there is on earth is mainly frozen in glaciers and ice caps. Only a tiny fraction of freshwater is found in groundwater, lakes and rivers or in the air.

But the view from the outside is deceptive: the Earth’s surface is largely covered by water, but measured against the diameter of the Earth, the oceans are only a wafer-thin layer. Therefore, the water makes up only a fraction of the Earth’s mass. By comparison, if the Earth were the size of a basketball, all the Earth’s water would fit into a ping-pong ball. And the drinking water would be proportionally even smaller than a single popcorn.

How did the water get on earth?

About two-thirds of the Earth is covered with water – a unique feature: the Earth is the only planet in the solar system that has liquid water. Life originated in water, and water is also vital for us humans. But where does the water on Earth actually come from?

Scientists suspect that the water comes from comets. These lumps of ice and dust originally formed at the edge of the solar system. Some, however, also fell into the interior of the solar system on orbits and became part of the freshly formed planets.

Then, as the earth slowly cooled, the steam turned back into liquid water. More vividly, it began to rain. These first downpours must have been stronger than any thunderstorm we can imagine today. And it must have rained for a very long time – several tens of thousands of years. Large parts of the young earth’s surface were flooded – in some places up to ten kilometres high. This is how the oceans were formed.

And what happened to the water on the other planets? Why are there no oceans there? Mercury doesn’t have enough gravity to hold an atmosphere at all – the water vapour simply escaped into space like all gases. The same thing happened on the moon. On Venus, the solar radiation is so strong that the water also evaporated out into space. On Mars, on the other hand, it is too cold, but large deposits of ice are suspected beneath the surface. And the gas planets have no solid surface on which seas could form. On Jupiter’s moon Europa, an ocean of water is suspected, but the surface is frozen. So the Earth remains the only celestial body in the solar system with seas.