Professor Martin Poliakoff of Periodic Videos explains the concept of differential expansion and why it causes ice cubes to crack when they are added to a drink.
When you drop ice into a drink, the drink is warmer than the ice. The outside of the ice warms up and expands, the inside is still very cold and can’t expand so it just cracks because part of it is trying to get bigger and part is staying the same. So there is essentially a tug-of-war between the inside and the outside and it gives way.
The concept is fully illustrated with a slow motion video of ice breaking in water and later in a related experiment, ice breaking in liquid nitrogen.
This time, the outside of the ice, instead of expanding, it contracts because it gets cold. The inside can’t contract quickly enough, so it shatters just in the same way it does in the drink. In fact, it shatters more dramatically than in water.
