Ask A Scientist
Why is ice slippery?
Asked by: Brock Carter
School: Johnson City School District
Teacher: Mrs. Goroleski
Hobbies/Interests: I love to go to the park.
Career Interest: Hockey Player
Answer from Douglas W. Green, EdD
Adjunct Lecturer, Binghamton University
Research Area: Leadership, Learning Theory and Social Media
Family: Daughter Lena, age 28, who is an animator for Nickelodeon in New York City
Interests/hobbies: Playing my banjo, biking, golf and reading
Web page address: http://www.drdouggreen.com
When two objects rub against each other, the molecules at the surfaces interact. The nature of the interaction will determine how easily the two surfaces can slip by each other. The amount of slipperiness depends on the attraction between the molecules, and how they are arranged. You have to push to get any object to move across any surface. We call the force that it takes to get one surface moving over another the force of friction.
If the surfaces are very smooth, you won't have to push very hard to get them moving. If at least one of the surfaces is rough, like sandpaper, it will take much more effort. Overcoming the force of friction also produces heat. You can feel this if you rub your hands together quickly over and over again. I often do this to warm my hands during the winter.
Ice is made of water molecules, which are very small as molecules go. They are the smallest molecules that can form a solid at temperatures we find on Earth. This makes for a very smooth, and slippery, surfaces when water freezes to make ice. If you wear skates, the friction from the skate will cause enough heat to melt the surface of the ice, making it even more slippery. This reduces the force of friction you need to overcome to get things moving.