How We Learned That Water Isn't An Element

Summary

The video explores the historical journey of understanding water’s composition. Initially believed to be an element, water was later shown to be a compound made of hydrogen and oxygen. Chemists in the late 18th and early 19th centuries discovered that water could be created by combining gases like hydrogen and oxygen, and they also found ways to split it through electrolysis. John Dalton's early work, including the first drawing of the water molecule, paved the way for the H2O discovery. The video emphasizes how great minds contributed to unraveling the mystery of water's molecular structure.

Takeaways

• 😀 Water was once thought to be a basic element of the universe.
• 😀 In the 1780s, chemists began observing that burning a peculiar gas produced a lot of water.
• 😀 Chemists built airtight vessels to separate water from atmospheric moisture to confirm whether water was created by combustion.
• 😀 The combustion of the gas in a sealed vessel produced only water, showing that water is not an element.
• 😀 Chemists discovered that water could be broken down into two gases through a process called electrolysis.
• 😀 By 1808, John Dalton proposed the first drawing of the water molecule as HO (hydrogen and oxygen).
• 😀 Experiments showed that water is made up of two volumes of hydrogen for every one volume of oxygen.
• 😀 The volume of gas experiments didn’t prove the ratio of hydrogen and oxygen molecules until it was discovered that gases consist of molecules.
• 😀 The key breakthrough was recognizing that equal volumes of different gases contain the same number of molecules, leading to the understanding that water is H2O.
• 😀 The water molecule is made of two hydrogen atoms and one oxygen atom, H2O, which was confirmed through experimentation and mathematical analysis.

Q & A

What was the early belief about water's composition?

People once believed that water was an element, a fundamental building block of the universe that couldn't be split into simpler substances.

What discovery did chemists make about water in the 1780s?

Chemists discovered that burning a peculiar gas produced a significant amount of water, leading them to question whether water was being created or if it was coming from atmospheric moisture.

How did chemists test whether water came from atmospheric moisture or the burning gas?

Chemists conducted experiments using airtight vessels sealed from the atmosphere. When they mixed the gas with another necessary substance and ignited it, the only product was water.

What did the experiment involving sealed vessels prove?

The experiment showed that water was not coming from the atmosphere but was being formed through the combustion of the gases in the vessel, revealing that water was not an element.

What is electrolysis, and how does it relate to water?

Electrolysis is a process that uses an electric current to split water into its two constituent gases, hydrogen and oxygen.

How did John Dalton contribute to understanding water's composition?

John Dalton, in 1808, made a drawing of the water molecule, suggesting that water was composed of one hydrogen atom and one oxygen atom, though this was later corrected.

Why was Dalton's initial drawing of the water molecule incorrect?

Dalton's drawing was incorrect because he did not yet have the necessary information about the ratios of atoms in a water molecule, and it was based on incomplete experimental data.

What key discovery clarified the ratio of hydrogen and oxygen in water?

The discovery that equal volumes of different gases contain the same number of molecules clarified that water is composed of two molecules of hydrogen for every one molecule of oxygen, forming the H₂O model.

What was the significance of the finding that gases like hydrogen and oxygen consist of pairs of atoms?

This discovery was crucial because it confirmed that two molecules of hydrogen gas and one molecule of oxygen gas combine to form water, supporting the H₂O composition.

How did chemists finally confirm that water's molecular composition is H₂O?

Chemists confirmed the molecular composition of water as H₂O by demonstrating that two molecules of hydrogen gas combined with one molecule of oxygen gas to form two molecules of water.