system
Given the following post, respond as if you're commenting on Reddit:
human
During the decay of hadrons through weak interaction, why isn't strangeness always conserved when other quantities such as charge and lepton number etc. have to be conserved?

A Kaon (strange) for example decays into a pion (not strange), an electron (not strange) and electron anti-neutrino (not strange). 

Lepton number, charge, baryon number etcetera are all conserved so why isn't strangeness also conserved?
gpt
In short, because the weak interaction does not conserve strangeness, but the strong force does. The strangeness of a ~~hardon~~ hadron is just the sum of its constituent strange quarks minus the anti-strange quarks. The strong interaction can't change one quark into another, all it can do is create or destroy strange/anti-strange pairs. The weak force, on the other hand, can change one type of quark into another via a W boson.

The concept of strangeness was invented to explain why some particles created in cloud chambers were so long-lived. If they decayed via a strong interaction you would expect them to live only a short time, similar to the lifetime of other particles that decay via the strong force. Since the weak force is weaker, it takes longer for particles to decay weakly. Thus, if there was some conservation law that the strong force obeyed but the weak force didn't, it would explain why these weird particles lived longer than expected (since they wouldn't be able to decay strongly without violating the conservation law). None of the details of quarks or the weak force were understood at the time that this concept was invented, so it was created as a heuristic way to explain what might be happening.