^^
i did, physic i kinda easy but chem... 
Chem like no see this type of question before leh...
The unknown substance is dunno what... contain so many
things?
They said it contains K, Br and O only, but our test shows more
substance in it -.-"
Burning the salt on a wooden splint - Purple flame.
First test, glowing splint relight, Oxygen is present.
Second test, add HNO3 then KI and then Starch.
HNO3 acidify the substance and then plus KI and give a yellowish
solution, Lead Is present in this test...
Then add starch, become purple... I dunno this is for what...
Thrid test, add AgNO3, white ppt is form, Chlorine is
present...
Then add ammonia, white ppt is again form, insouble in excess,
which means it contain either lead(II)or Aluminium.
Fourth test, add AgNO3, again white ppt is form, Chlorine is
present...
Then add ammonia, white ppt, soluble in excess. You will see that
become colourless after your add the 1cm^3 of ammonia... 1cm^3 of
ammonia is enough to see it become colourless... This shows Zinc is
present...
HOWEVER,
this is just what i wrote in my paper and there are A LOT OF ERRORS
HERE!
so dun be sad if different as yours...
