Sodium

When sodium reacts with water,what visible changes can be observed?And please explain the changes.
Ans:
Firstly Na dissolves in water due to the weak metallic bond(of course giving a low melting point also).Since it has only 1 outermost shell e-, this means that only 1 e- takes part in formation of metallic bonds. Besides its size is large, the attraction between the outermost shell e- by the nuclear charge generated by the nuclear will become weaker. (when no.quantum shell [= K,L,M,N shells] increases down the group, effective nuclear charge decrease, due to outermost shell e- well shielded by the inner shell e- and nuclear attractive force attracting the outermost shell e- decreases.). The generated heat energy during the reaction with water make the Na metal melt.
Secondly it gives golden yellow flame.
Thirdly it gives hissing sound.
fourthly it dashes around the water surface
Fifthly you CAN'T SEE H2 gas produced since it is colourless and only burning it will make you know it is H2 gas if it has a POP sound.

If the sodium moves around on the water surface,what is the reason about that
Ans:
Since it is loosely packed (body center cubic B.C.C), its density is low making it keep afloat in water. The loosely package makes it have some spaces that H2 can become from its spaces when its base is touching with water. The formed H2 gas give the low density metal a proplusion force so that it move about the water surface.妤像放一個充滿氣的氣球一樣,氣球被放出的氣所推進.

e- = electrons
no = number

I hope my information can help you.

1)sodium melted to form a silver ball, and it floats on water, colourless gas bubbles evolved, some vapour may occur.

sodium reacts readily with water to form sodium hydroxide and hydrogen gas, and this reaction is highly exothermic, as sodium has a low melting point, during the reaction, the heat produced melt sodium into a silver ball.
As hydrogen(the colour gas bubbles) is formed, it provides an upthrust and allows sodium to float.
As a large amount of heat is produced, the heat may be enough to boil the water into vapour.

2)Due to random motion of water molecule in the water tank.
This is because according to the kinetic theory of particles, each particle posseses a certain amount of kinetic energy and the energy allows them to move within the container randomly.

Hope they are correct...