# Why is the formation of slacked lime accompanied by a hissing sound and the formation of bubbles?

My teacher made me write that that the formation of calcium hydroxide (slacked lime) from calcium oxide (qucklime) is described as

$\ce{CaO + H2O -> Ca(OH)2}$

and that the process

1. forms bubbles
2. is an exothermic reactions
3. makes a hissing sound

Why does it make a hissing sound and form bubbles?

There is no gas evolved in the reaction, then why does formation of bubbls take place?

And what is the reason of the hissing sound being produced?

• Because your teacher is wrong? The observations sound like the observations of $\ce{Ca + 2H2O -> Ca(OH)2 + H2}$. – DHMO Oct 1 '16 at 9:24
• Because the reaction is so exothermic that the water starts boiling? – Ivan Neretin Oct 1 '16 at 9:26
• No $\ce{H2}$ gas evolves. – MaxW Oct 1 '16 at 12:06
• ?? everyones confused – MartianCactus Oct 1 '16 at 15:24
• This reaction is exothermic enough to be used for self-heating food packaging. That's going to cause some sizzling in the water. – Zhe Oct 4 '16 at 1:57