Ice plays a very big role in how a drink tastes. Smaller cubes will melt a lot faster than larger cubes so a whiskey served with small ice cubes will taste great at first but soon become diluted and watery in taste. Another important factor is the temperature of your ice; if you keep ice in an ice bucket it can start to sweat. Any ice cube that has already started to sweat will melt faster than an ice cube that is freshly made or has been stored in the freezer. Round ice cubes will melt a lot slower than cubed ice so your whisky takes a lot longer to become too diluted. A sphere exposes less surface area for the same amount of volume as a cube of ice. So, if you have a cube that is the same volume as a sphere, the sphere will actually have a lot less surface area, over 24% less. The less surface area that is exposed to the room temperature liquid, the slower the ice will melt. Therefore, a sphere of ice will melt more slowly in a drink than a cube of ice. This way, you can chill the drink without quickly diluting it.