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 )
This is fairly easy for a blockchain analysis company to trace.
Blockchain analysis companies obviously know about the existence of these instant exchangers, and also know that they are popular for swapping bitcoin to other coins. They also know how they work, know the fees they charge, and probably have identified their wallet addresses on multiple chains. If they see you sending $100 worth of bitcoin to one of them, and then a few minutes after it is confirmed they see $98 worth of litecoin leave, then they can link those transactions together. If you send all the litecoin to the same address, then they can probably work backwards and link all your bitcoin transactions together too.
If you don't want to be traced, then you'll either need to mix or coinjoin your bitcoin first, or swap it for monero which cannot be traced in this way.