Alaikum Assalam. First of all you are right mashallah your niece looks very cute and sweet.You showed your niece how if you add salt in water the egg floats and the egg does not float in plain water. I myself was surprised by this scientific work. And the expression on your niece's face shows how interested and happy she is doing the scientist work. Blessings for you and your niece.

Regards friend. ❤️