Ape EDITION SI, Sigh! To measure out a second, time how long it takes for an electron in a cesium atom to change energy levels 9, 192,631,770 times. To map out a meter, measure the distance light travels in a vacuum during 1/299,792,458 of a second. To calibrate a kilogram, travel to France and balance their kilogram weight against yours. For more than a century, the world's "official" kilogram and its six identical copies have sat in the Bureau International des Poids at Mesures in Sevres, France. This small cylinder made of 90% platinum and 10% iridium was kept inside three nested bell jars inside a vault inside the basement of the Bureau International. Three different keys held by 3 different people were needed to open the climate-controlled vault because this important hunk of metal could never be allowed to get scratched, dusty, or in any way lose or gain an atom. In 1889, 1946, and 1989, the "official" kilogram was compared with its copies. In 1889, the masses were the same. One hundred years later, the "official" weighed one sugar grain less than the copies. No one knew if the original was losing weight or the copies were just gaining weight faster, but either way, this difference was problematic. In 2019, the Conference on Weights and Measures has met and decided that the kilogram (as well as the ampere, Kelvin, and mole) can finally be redefined based on abstract constants in nature rather than physical objects. After May 20, 2019, the SI unit for mass will be defined using electrical and magnetic forces. A scale called a Kibble balance measures the amount of electricity needed to create a force (through a magnetic field) that counteracts the weight of an object. The balance determines current by measuring resistance and voltage which are related, indirectly, through Planck's constant. Therefore, by placing a known mass in the Kibble balance, the exact value of Planck's constant could be determined. And, armed with this exact value of Planck's constant, the Kibble balance can be used to find an unknown mass. The NIST-4, an extremely precise Kibble balance, will become the US's next kilogram standard. Similar to its low-tech international predecessor, NIST-4 lives underground in an environmentally controlled complex inside the National Institute of Standards and Technology. Questions: 1. How was a kilogram defined prior to 2019? 2. Why did this definition need to be changed? 3. How will the kilogram be defined after May 20, 2019? 4. Is mass an extrinsic or intrinsic property?APO EDITION 6. Would extrinsic or intrinsic properties be more useful in identifying a substance? Why? 7. What else would you like to know about the liquid from the baby bottle? How do you think you can find out this information