How to teach random number generator algorithms?
So much depends on the language or library you are using. If the tool you are using allows feeding a specific seed I would start by demonstrating how using the same seed gives the same set of random numbers each time. If not and the tool uses the system time as the seed, as many do, then create several random data sets if a very tight look and show how they are the same.

This cre3ating several random sets in a tight loop is something students often do by accident BTW. It gives them no end of trouble as they see identical numbers for all of them.

Then demonstrate how the same code gives different (from the first example) random numbers when used with a different seed.  

With your example, using a random number from the same seed would return the same word every time. Using a time based seed should normally return a different word each time.

BTW random.org is a useful/interesting site on the topic. They go into some detail on random and pseudo-random numbers at https://www.random.org/randomness/