Simulation when population means are equal (H0)
This simulation shows the calculations for finding the p-value for a 1-tailed test and illustrates that any p-value between 0 and 1 is equally likely when the group means are equal.
Again stress that:
The p-value cannot provide a definitive answer
There is always some chance of being misled by an 'unlucky' sample.
Take several samples. Mention that in about 1/20 of the samples, the p-value will be less than 0.05, etc.
There is a (small) probability that the p-value will misleadingly suggest that the second group mean is higher.