Why does club soda make ice cubes freeze together?

Question

I mix club soda w/Coke. If I add the coke first, the ice cubes easily move around. If I add the club soda first, the ice cubes fuse together and I have a frozen mass. Why does club soda make ice cubes freeze together?

Answer 1

Soda is more like pure water than coke (which has sugars, flavourings, vegetable extracts, etc all added in).

Pure water has a freezing point of 0oC - and the ice cubes, having come from a freezer, are going to be lower than that.

Coke - with its additives - will have a freezing point lower than 0oC (this is why salt "melts" ice - it actually lowers the water's freezing point).