Re: My son found plans to fuel a vehicle w/water. Is this feasible & dangerous?

Technically, you can break down water into hydrogen and oxygen and then re-
combine them in an engine such as a go kart or lawn mower engine.  But you 
won't get much power from the hydrogen.  Companies like 
BMW are trying to make vehicles powered by hydrogen but the storage of the 
gas and potential for danger put it out of reach for most technical people 
let alone a 12 year old boy.  I think I found the web site you referred 
to, and it seemed like a way for them to sell plans and make money.  As 
long as they don't go on to claim anything too wild, they can sell a lot 
of plans and avoid being sought after for fraud.  

I would encourage him to build a scale model car with an electric motor 
powered by a small solar cell.  If he can tackle that, maybe he can go on 
to bigger things.  When I was not much older than him, I designed a way to 
adapt a lawn mower engine to my bicycle. It worked for about a minute 
before it threw the chain, but I did go on to a career in mechanical 
engineering.  There are also mouse trap powered vehicle competitions and 
other design tasks that would encourage him to practice design and the 
career of engineering.

I recall breaking down water into hydrogen and oxygen in my high school 
chemistry lab and we still had to wear safety masks and worry about the 
bottle exploding in our hands.  You might ask a high school science 
teacher if they can still do this as a demonstration.  If you could demo 
it for him or let him see it, it might underline the danger.

I shared his desire for a go cart at his age, so I can understand the 
interest.  If he can turn that interest into real practice, maybe he can 
enter the world of mechanical engineering.