x, y, z
 

hey i have a question,

a shiny malleable substance(metal), which is an excellent conductor of electricity, is burned in air to produce a white solid(y). when this solid is placed in water, it slowly dissolves to form a colourless solution(z)
-what kind of substance is y?
-what kind of substance is z?
:? ...

I don't know the answer. However I can think of ways to approach the problem. Why don't we work on it together.

What sorts of metals burn in air?

What happens to the chemical composition of a substance when it is burned in air?

If you answer those, then I'll help you some more.

Could the metal be Sodium?
Y is sodium oxide?
Z is sodium hydoxide?

Isn't sodium only reacts with water? (4Na+2H2O - 2Na2O+2H2O). When Metal burns in the air, it usually creates oxide compound. Does it burn slightly when touching air? probably Carbon

I know magnesium burns in air. Maybe that's it.

But magnesium burn in the air with the help of fire. try this simple experiment, Magnesium strip with flame, white light coming out of it (DON'T look at it). it Produces magnesium oxide.

Re: x, y, z
 

My best guess at this point is still magnesium. This site says that it's a shiny and soft metal:

http://www.chemsoc.org/viselements/p...sium_data.html

The periodic table on this site says that when it is burned in air (and it does burn in air quite brightly) MgO and Mg3N2 are formed. Generally, to burn something in air means to react it with oxygen gas to form the oxide.

This site says that MgO is a white solid:

http://www.magspecialties.com/students.htm

This site says that when MgO is place in water, it becomes milk of magnesia, the chemical formula of which is Mg(OH)2:

http://hyperphysics.phy-astr.gsu.edu...pertab/mg.html

As a metal, magnesium will be a good conductor of electricity.

Therefore x=Mg, y=MgO, and z=Mg(OH)2 (aq), I think.

solid
 

The metal you are referring to could be any of the alkali metals (group 1 metals-see the periodic table for the whole list).

Sodium being itself a group 1 metal is a good example. Since elements in the same group have similar chemical properties and chemical reactions, any other group 1 metal would do as well. These metals are usually soft meaning that they are malleable. They also have a lustrous appearance. The oxides of these metals are also soluble in water to give soluble bases called alkalis hence their name as alkali metals. These features fit the description of the metal that you want.

So, substance Y would be the oxide of a group 1 metal and substance Z would be the hydroxide of a group 1 metal.

every metal burns, just depends on the temperature.
uranium starts burning at quite low temperatures and is therefore used (among other reasons) in tank-anti tank ammunition.

the only hint you have here, is that not everey metaloxide is solutable in water, which is a good hint that the metal is alkali or earthalkali

group I metals soft and malleable
group II metals hard and malleable

therefore neither group I nor group II metals eliminated...

out of group I metals all oxides dissolve rapidly in water
out of group II metals some of the oxides dissolve reasonably in water such as barium and strontium.

however the question reads...

"what KIND of metal is x?"

therefore it is a reactive metal that has a basic soluble oxide - no further specification is possible