I need reaction on heating this salts in test tube - KCl,Al2O3 and SnO2

And also if can explain the observations and Remarks why so happened

It would help if we knew what your observations were.

KCl gave a cracking sound underwent melting and again solidified on cooling.

,Al2O3 on heating no changes found and sno2 give slight yellow colour and again turned to white

Are you able to reproduce it?

 

If so, record it on video using digital camera, full hd preferably for good quality.

 

Are you using solids only, or they're dissolved in water or other liquid.. ?

 

What is mass of each of them.. ?

You said, test tube, so I assume there is very small amount of them.

Typical test tube has just 20-25 mL volume.

 

What if you replace KCl by NaCl.. ?

There is usually some water content in the crystals of KCl if left exposed to the atmosphere. When heated rapidly, water vapour escapes suddenly cracking the crystals(with a sound, of course). I wouldn't expect it from anhydrous sample.

KCl melts at 770 C and alumina at above 2000 C. You might not have reached the temperature needed to melt alumina.

regarding SnO2 it could possibly be due to similar processes seen in ZnO(see wiki)