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Atomic Mass Unit

Standard unit based on Carbon-12, 1.66 x 10^27 kg

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Origins of the AMU

License: CC BY-NC 3.0

The Prototype Kilogram [Figure1]

Atomic Mass Unit

People measure mass in grams, but how much is exactly 1 gram? Could we recreate the gram if every gram measuring tool was removed from the earth? We actually could. Did you know that a gram was initially defined as “the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice”? Now the definition has changed slightly, but the atomic mass unit, or Dalton, shares similar roots. An atomic mass unit is defined as “one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state”.

Creative Applications

1. Why do scientists use the atomic mass unit?

2. What is the conversion rate between grams and the atomic mass unit?

3. What is the atomic mass unit most similar to in mass?

4. How is the meter defined?

5. The gram is now defined in a new way. What is this new way?

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