On 5 June 1783, Joseph and tienne Montgolfier used a fire to inflate a spherical balloon about 30 feet in diameter that traveled about a mile and one-half before it came back to earth. News of this remarkable achievement spread throughout France, and Jacques-Alexandre-C�sar Charles immediately tried to duplicate this performance. As a result of his work with balloons, Charles noticed that the volume of a gas is directly proportional to its temperature.
V a T
This relationship between the temperature and volume of a gas, which became known as Charles' law, provides an explanation of how hot-air balloons work. Ever since the third century B.C., it has been known that an object floats when it weighs less than the fluid it displaces. If a gas expands when heated, then a given weight of hot air occupies a larger volume than the same weight of cold air. Hot air is therefore less dense than cold air. Once the air in a balloon gets hot enough, the net weight of the balloon plus this hot air is less than the weight of an equivalent volume of cold air, and the balloon starts to rise. When the gas in the balloon is allowed to cool, the balloon returns to the ground.
Charles' law can be demonstrated with the apparatus shown below. A 30-mL syringe and a thermometer are inserted through a rubber stopper into a flask that has been cooled to 0�C. The ice bath is then removed and the flask is immersed in a warm-water bath. The gas in the flask expands as it warms, slowly pushing the piston out of the syringe. The total volume of the gas in the system is equal to the volume of the flask plus the volume of the syringe. The table below contains typical data obtained with this apparatus.
The Dependence of the Volume of a Gas on its Temperature
Temperature (�C)
Volume (mL)
0
107.9
5
109.7
10
111.7
15
113.6
20
115.5
25
117.5
30
119.4
What is Charles' law?
Theodore G. Lindeman, professor and chair of the chemistry department of Colorado College in Colorado Springs, offers this explanation:
The physical principle known as Charles' law states that the volume of a gas equals a constant value multiplied by its temperature as measured on the Kelvin scale (zero Kelvin corresponds to -273.15 degrees Celsius).
The law's name honors the pioneer balloonist Jacques Charles, who in 1787 did experiments on how the volume of gases depended on temperature. The irony is that Charles never published the work for which he is remembered, nor was he the first or last to make this discovery. In fact, Guillaume Amontons had done the same sorts of experiments 100 years earlier, and it was Joseph Gay-Lussac in 1808 who made definitive measurements and published results showing that every gas he tested obeyed this generalization.
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It is pretty surprising that dozens of different substances should behave exactly alike, as these scientists found that various gases did. The accepted explanation, which James Clerk Maxwell put forward around 1860, is that the amount of space a gas occupies depends purely on the motion of the gas molecules. Under typical conditions, gas molecules are very far from their neighbors, and they are so small that their own bulk is negligible. They push outward on flasks or pistons or balloons simply by bouncing off those surfaces at high speed. Inside a helium balloon, about 10 (a million million million million) helium atoms smack into each square centimeter of rubber every second, at speeds of about a mile per second!
Both the speed and frequency with which the gas molecules ricochet off container walls
Charles's law
Relationship between volume and temperature of a gas at constant pressure
Charles's law (also known as the law of volumes) is an experimental gas law that describes how gasestend to expand when heated. A modern statement of Charles's law is:
When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be in direct proportion.
This relationship of direct proportion can be written as:
So this means:
where:
This law describes how a gas expands as the temperature increases; conversely, a decrease in temperature will lead to a decrease in volume. For comparing the same substance under two different sets of conditions, the law can be written as:
The equation shows that, as absolute temperature increases, the volume of the gas also increases in proportion.
History
The law was named after scientist Jacques Charles, who formulated the original law in his unpublished work from the 1780s.
In two of a series of four essays presented between 2 and 30 October 1801,John Dalton demonstrated by experiment that all the gases and vapours that he studied expanded by the same amount between two fixed points of temperature. The Frenchnatural philosopherJoseph Louis Gay-Lussac confirmed the discovery in a presentation to the French National Institute on 31 Jan 1802, although he credited the discovery to unpublished work from the 1780s by Jacques Charles. The basic principles had already been described by Guillaume Amontons and Francis Hauksbee a century earlier.
Dalton was the first to demonstrate that the law applied generally to all gases, and to the vapours of volatile liquids if the temperature was well above the boiling point. Gay-Lussac concurred. With measurements only at the two thermometric fixed points of water (0°C and 100°C), Gay-Lussac was unable to show that the equation relating volume to temp
Jacques Charles
French inventor, scientist and mathematician (1746–1823)
Jacques Alexandre César Charles (12 November 1746 – 7 April 1823) was a Frenchinventor, scientist, mathematician, and balloonist. Charles wrote almost nothing about mathematics, and most of what has been credited to him was due to mistaking him with another Jacques Charles (sometimes called Charles the Geometer), also a member of the Paris Academy of Sciences, entering on 12 May 1785.
Charles and the Robert brothers launched the world's first hydrogen-filled gas balloon August 27, 1783; then December 1, 1783, Charles and his co-pilot Nicolas-Louis Robert ascended to a height of about 1,800 feet (550 m) in a piloted gas balloon. Their pioneering use of hydrogen for lift led to this type of gas balloon being named a Charlière (as opposed to the hot-airMontgolfière).
Charles's law, describing how gases tend to expand when heated, was formulated by Joseph Louis Gay-Lussac in 1802, but he credited it to unpublished work by Charles.
Charles was elected to the Académie des Sciences in 1795 and subsequently became professor of physics at the Académie de Sciences.
Biography
Charles was born in Beaugency-sur-Loire in 1746. He married Julie Françoise Bouchaud des Hérettes (1784–1817), a creole woman 37 years younger than himself. Reportedly the poet Alphonse de Lamartine also fell in love with her, and she was the inspiration for Elvire in his 1820 autobiographical Poetic Meditation "Le Lac" ("The Lake"), which describes in retrospect the fervent love shared by a couple from the point of view of the bereaved man. Charles outlived her and died in Paris on 7 April 1823.
Hydrogen balloon flights
First hydrogen balloon
Charles conceived the idea that hydrogen would be a suitable lifting agent for balloons having studied the work of Robert Boyle's Boyle's Law which was published 100 years earlier in 1662, and of his contemporaries Henry