Lots of explanations given are fun but requires much more mathematical maturity to understand and digest... I would just write it the expanded way:
x^2 = x*x
x^3 = x*x*x
Therefore, x^2*x^3 = (x*x) * (x*x*x) = x^5 (assuming your students already know the exponential notation of course).
In the end, it's just a property of multiplication and all other examples are kind of multiplications in disguise but the disguise makes them more difficult to grasp!