I would like to know if i use Instant Exchange https://exch.cx/ and convert my bitcoins to litecoin, will it serve as a mixing too and my coins can't be traced (act as a mixer) ?
Meaning if i do multiple transactions using that Instant Exchange and convert Bitcoin to Litecoin. (The destination address of LTC remains the same in all the transactions )
If, as you said , destination address in all transactions is the same, then the mixing via https://exch.cx/ has no sense,you will be traced by chain-analysis agencies. On the other hand if those addresses are different and you will make a few swap rounds using Instant Exchange/s as well a few intermediate transactions (that don't reuse addresses) between those rounds then your coins will become less traceable.
Chain-analysis uses heuristics to trace coins thus, in my view, it would be helpful if you could read the relevant guide divided into four parts iurl=#ANK01][1][/iurl], [2], [3] and [4].