Subject: Salt is often put on icy sidewalks to melt the ice. How does this work?

My science ed. group just taught a lesson on matter to a third grade class. In 
our last lesson, we made ice cream. We put the food ingredients in a small 
plastic bag, which we placed in a bag with ice and rock salt. We were under the 
impression that the rock salt made the ice colder, which sped up the process of 
ice cream making. If the salt makes the ice colder in the bag, then how does 
the salt melt ice on sidewalks? Wouldn't it just make the ice colder? I'm 
stumpted! Thanks! :)

Re: Salt is often put on icy sidewalks to melt the ice. How does this work?