Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
The second (s) is the base unit of time in the International System of Units (SI). It is defined by taking the fixed numerical value of the cesium-133 atom's ground-state hyperfine transition frequency.
5 Must Know Facts For Your Next Test
The second is one of the seven base units in the SI system.
It is precisely defined using atomic clocks, which measure the vibrations of cesium atoms.
The symbol for seconds is 's'.
This unit is essential for determining rates and speeds in chemical reactions.
Time measurements are crucial for understanding reaction kinetics and dynamics.
Review Questions
Related terms
Minute (min): A unit of time equal to 60 seconds.
Hour (h): A unit of time equal to 60 minutes or 3600 seconds.
Frequency (Hz): The number of occurrences of a repeating event per unit time, measured in hertz (Hz), where one Hz equals one cycle per second.