I believe the best way to explain a key component of chemistry to children who are very young to know what chemistry even is, is to say the following:
"Avogrado's number actually has a name. It is called 'mole' and it is like one, two, five, and any numbers you can think of. Now, mole is a big number. It is bigger than two; it is bigger than 22 and counting it will take you many years. But this big number is important because it helps us study tiny specs in our universe, like atoms and molecules. What are these? They are smaller than your toes, smaller than dust, and even smaller than the smallest of dust in your toes. But they are important because they are the reason why we are here today."
Avogrado's number/mole is definitely more complicated than what was written above, but since it's kindergarten students that are listening, it has to be simplified in order for them to understand. I used simple English and fun phrases/comparison in order to make the speech sound more appealing to a younger audience.
