Since it’s known that solid objects are denser and have more weight than liquids – and ice is a solid – one would automatically think that ice would sink in water. But it doesn’t! What’s so special about ice that causes it to float?
Believe it or not, ice is actually about 9% less dense than water. Since the water is heavier, it displaces the lighter ice, causing the ice to float to the top.
How is ice less dense than water?
When a liquid is cooled, more molecules are brought closer together and need to be accommodated in a smaller area. This results in most solids having a greater density than liquids. Not so with ice.
Water consists of positively-charged hydrogen atoms and negatively-charged oxygen atoms. When water cools, the hydrogen bonds adjust to hold the negatively-charged oxygen atoms apart, which prevents the ice from becoming any denser.
So for water, the density actually decreases along with a decrease in temperature – causing ice to be less dense than water!
A gift to nature
When looking at this concept in nature, we see how important it is:
Lakes and rivers freeze from top to bottom, enabling fish to survive even after the surface of the body of water they live in has frozen over.