Why are cracks formed in ice cubes when this get in contact with a liquid?

Question

Why are cracks formed in ice cubes when this get in contact with a liquid?

Answer 1

Because the ice is warmed and expands like any other solid.  Since ice is brittle it cracks, just like a dish when you put something too hot on it.  

Answer 2

It's because of the temperature difference between the ice and the liquid. A drink, even a cold one, is warmer than the ice cubes, and when an ice cube is dropped in the ice starts to warm up. This warming is uneven - the outside of the cube heats up faster than the inside because it's directly exposed to the liquid. This means the ice crystals at the surface expand more than the ones inside, which creates stresses that crack the brittle ice.