Battery life decreases during in the cold.
Some studies suggest 20-40% reduction, although in modern batteries this is only temporary. This is due the the atoms (or ions in the case of batteries) randomly moving at a slower pace. We must thus impart them with more energy to make them move. A representation is trying to get something over a hill. We need to impart force to get them is, and after the crest of the hill they can “travel” the rest themselves. Thus the crest represents a threshold which must be crossed be movement is imparted. The cold weather essentially increases the steepness of the slope on the “hill.”

Salt lowers the melting point of water.
Link. Also, seemingly grit has little to no effort on it’s own, it’s simply used to bulk up the salt being spread and it serves as a physical sidekick to help mash the salt into the ice. This is because the rock salt is practically useless if it’s just sitting on top of the ice.

View from the top of the world’s tallest tower (Burj Dubai) - Youtube link

And to finsih: How long is a piece of string?

-Brian (bhc at lifescience dot ie)