Science · Chemistry
Chapter 1: Matter and Measurement
Every digit is a claim.
In 1894 Lord Rayleigh weighed a glass globe filled with nitrogen taken from air, then with nitrogen made from chemical compounds. The gas from air weighed 2.3102 g; the gas from chemicals weighed 2.2990 g.
The difference is 0.0112 g, about half a percent. Should it be rounded away?
Make your guess to turn the page.
Still to come: 8 pages · Lab · Words to Know · What We Learned · 4 questions · Explain It in Writing · Open Questions
The idea this lesson is working on — Students treat significant figures as a marking convention that throws accuracy away, so keeping every calculator digit feels safer. The book sets the lab, where a caliper reading gives 47.6354 cm² from two three-figure measurements, against Rayleigh, where the fourth figure was a discovery. Ask: which digits did an instrument actually resolve? The idea to reach is that a digit is a claim, and rounding is declining to invent.
The sources, and a note on the lab — Rayleigh’s globe masses (2.3102 g from air, 2.2990 g from chemical sources) are the figures usually quoted from his 1894 work with Ramsay, and both received Nobel Prizes in 1904. The simulation records each reading to the finest marking (12 cm with a centimeter stick), where many chemistry courses would read one estimated digit further (12.5 cm). It also writes the one-figure area as 50, which the limits page explains.