John Dalton as...
John Dalton in...
John Dalton Man of Action!
...Featuring John Dalton
| THIS WEEK'S EPISODE: There's Trouble Afoot
in the Land of Double Double Replacements
The Challenger: Potassium iodine + lead nitrate and his sidekick, silver nitrate + potassium chloride The Defender: John Dalton Man of Action |
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View the movie below |
A little background:
John Dalton was a chemist born in Eaglesfield, England. Among his scientific activities was the keeping of a meteorological journal in which he amassed over 200,000 observations.
His contributions to atomic theory included the return to Democritus's theory of tiny indivisible particles called a-toms or atoms that make up the most basic units of matter. Unlike Democritus's theory, however, Dalton's view of the atom was based on experimental observations.
The experiment:
Two double replacement reactions, potassium iodine + lead nitrate and silver nitrate + potassium chloride, which are illustrated by the following formulas.
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2 KI + PbNO3 -----> K2NO3
+ PbI2
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Ag2NO3 + 2 KCl
-----> K2NO3 + 2 AgCl2
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Materials:
Four 250 mL beakers, two 500 mL beakers. 100 mL of all four above substances.
Procedure:
In each of the 250 ml beakers, put 100 ml of each substance. Slowly add the potassium iodine and the lead nitrate simultaneously into the larger 500 ml beaker. The chemicals should change from clear to white.
Repeat these steps with the silver nitrate and the potassium chloride. This reaction should turn the chemicals from clear to yellow.
Life in Dalton's time:
Cultural Fact: In Feb. 21, 1787, Congress approved a convention in Philadelphia to revise the Articles of Confederation.
Scientific Fact: James Rumsey designed first mechanically driven boat.
Social Fact: Mozart's opera Don Giovanni was first performed October 29, 1787.
Question: In this experiment, what do the color changes indicate?