John Dalton; Atomic Theory

Atomic Theory:Dalton’s Law of Partial Pressures

Year of:October 1803
Place of discovery:

While studying the nature and chemical makeup of air in the early 1800s, Dalton learned that it was not a chemical solvent, as other scientists had believed. Instead it was a mechanical system composed of small individual particles that used pressure applied by each gas independently Dalton's experiments on gases led to his discovery that the total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space.

4 Random Facts

*John Dalton was born September 6, 1766, in Eaglesfield, England

* John Dalton was color blind

*he was the first scientist to explain the behavior of atoms in terms of the measurement of weight

*died July 26, 1844

The importance of John Dalton

Dalton's interest in atmospheric pressures eventually led him to a closer examination of gases. While studying the nature and chemical makeup of air in the early 1800s, Dalton learned that it was not a chemical solvent, as other scientists had believed. Instead it was a mechanical system composed of small individual particles that used pressure applied by each gas independently.

Dalton's experiments on gases led to his discovery that the total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space. In 1803 this scientific principle officially came to be known as Dalton's Law of Partial Pressures. Dalton's Law primarily applies to ideal gases rather than real gases, due to the elasticity and low particle volume of molecules in ideal gases. Chemist Humphry Davy was skeptical about Dalton's Law, until Dalton explained that the repelling forces previously believed to create pressure only acted between atoms of the same sort, and that the atoms within a mixture varied in weight and complexity.

The principle of Dalton's Law can be demonstrated using a simple experiment involving a glass bottle and large bowl of water. When the bottle is submerged under water, the water it contains is displaced, but the bottle isn't empty; it's filled with the invisible gas hydrogen instead. The amount of pressure exerted by the hydrogen can be identified using a chart that lists the pressure of water vapors at different temperatures, also thanks to Dalton's discoveries

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