Sometimes (ok, a lot), Alex continues with a specific line of questioning until the answer I give is inevitably "I don't know" or "let's ask Dad". Sometimes (ok, a lot) this is because I genuinely don't know or genuinely want his dad to answer, but often it's because I can't think of a way to explain the real answer in simple enough language to both satisfy his curiousity and prevent a further line of questioning.
Alex was in the bath running water through his hands and the conversation went something like this.
A: Mum, why is water wet?
Me: Because it's a liquid.
A: You can't carry liquid can you?
Me: Well, you can if you put it in something solid like a cup.
A: Are toys solid?
A (holding a big round bubble from the bath on the flat of his palm): Yook! I'm carrying bubbles. Is a bubble liquid?
Me: Let's ask Dad.
Dad proceeded to dazzle us with explanations about the surface of the bubble forming a meniscus and therefore being a liquid that was in fact able to be carried without a supporting solid apparatus. Glad we got that sorted out. Did I mention Alex is 3?