When throwing items in lava, the items will catch fire and bounce a little before getting destroyed.
The item touches the lava and gets destroyed instantly.
The item touches the lava and gets set on fire. Then, the item bounces off of the lava.
How to reproduce:
1. Create a 1 by 1 hole in the ground and place a lava source in the hole.
2. Throw a item onto the lava source. You will notice that the item lands onto the block next to the lava.