Question:  Why did we only fill the inner can half full of the ice cream mix? Was it because the mix expands as it changes to ice cream? After we duct-taped the can with the mix shut in a larger can, filled with layered salt and ice we rolled it back and forth on ground for about 20 minutes. Why does this help? How does it help make the ice cram smooth rather than full of noticeable ice crystals? (One of the lab groups refused to roll the can, so that's what theirs looked like compared to ours?

Answer:  I imagine that the reason you only filled the inner can half full was so that the ice cream would slosh around (keeping large ice crystals from forming) and would also pick up some air bubbles, giving it a lighter texture.

Question:  How do you explain the rapid increase in the amount fo the water in the can? Did the salt cause the ice to melt faster?

Answer:  The salt caused the ice to melt faster.  Because the addition of salt to ice causes the ice's melting point to decrease, it would melt more quickly under normal conditions.