Simplify the following text for a Grade 9 native English-speaking person.
Original: As an analogy , on the surface , some snowballs might appear to be solid snow , but instead , a snowball can contain a large rock or stone , inside , which is revealed only when it melts .
Simplified: As an analogy , on the surface , some snowballs might appear to be solid snow , but instead , a snowball can contain a rock or stone , inside , which is revealed only when it melts .