When sodium metal is added to cold water, the metal melts to form the shape of a ball and quickly moves about the surface of the water. Hydrigen gas is rapidly produced and sodium hydroxide solution (an alkali) is formed.
a) How can hydrogen gas be identified? (Burns with a pop?)
b) Why does the metal melt?
c) What metal reacts more vigorously than sodium with water?
d) What indicator could be added to confirm the presence of an alkali? (universal indicator?)
Surely in the time it took you to type out the question you could have looked in any school science text book or searched on the web for information about alkali metals. I am certain you'd learn more by researching it yourself.
Reactivity with water increases up group One of the periodic table, the alkali metals.
So in terms of reaction you have Sodium, Potassium, Rubidium, Caesium and Francium.
There is a fantastic program from The Open University of a chemist dropping bits of these metals into water, well the first few anyway. you might find it on YouTube
I would love to see the Francium reaction, if you could get enough of it together in one place (unlikely)