When winter weather hits and ice and snow abound, all sorts of surfaces can get slick and slippery. If you’re a driver, this is not such a good thing. Ice and snow can make driving treacherous.
Of course, if you want to go sledding, it’s a great thing! When it comes to sliding down a hill on a sled or a toboggan, you want the snow to pack down into ice that’s as slick as possible.
No one would deny that ice is slippery, but have you ever thought to wonder why? After all, ice is a solid, right? Can you think of any other solids that are slippery?
Think of a hockey player for a moment. Can you imagine trying to skate on a concrete sidewalk? How about a wooden floor? These are solids, too, so why aren’t they slippery?
After years and years of research, scientists can explain what makes ice slippery…but not exactly why. So what makes ice slippery? The answer is definitely water — the liquid form, not the solid!
Scientists have discovered that a very thin layer of liquid water exists at the outermost edge of ice — even ice that is extremely cold. For years, scientists believed that this thin layer of liquid water was the result of pressure being applied to ice.
Water has an unusual property: its solid form (ice) is less dense than its liquid form. This is why ice cubes float in a glass of water. The lower density of ice means that its melting temperature can be lowered by applying pressure.
So, for example, when an ice skate glides over ice, scientists once believed that the pressure applied by the skate would lower the melting point of the solid ice. This would cause the outermost layer to melt. The skate would then slide across on a thin sheet of water that would immediately refreeze as soon as the skate passed.
Unfortunately, scientists later discovered that the pressure applied by skates or people’s shoes standing on ice was not great enough to cause these changes. So, they had to look for another explanation. In recent years, two other theories have been developed to explain the presence of the thin liquid water layer that exists on ice.
One of these theories is that friction causes the liquid layer of water to form on ice. Friction is the force that generates heat whenever two objects slide against each other. If you rub your hands together, you can feel them heat up. That’s friction at work. When a skate moves over the surface of ice, the friction between the skate and the ice generates heat that melts the outermost layer of ice.
But ice is still slippery even when you’re standing still. If you stand on ice without moving, no friction exists to generate heat, yet the ice is still slippery. So there must be something else going on.
The other theory is that ice is just slippery, because the outermost layer never turns to a solid. According to this theory, the water molecules at the surface of the ice move more, because they’re at the edge and there aren’t any molecules above them to help keep them in place. As a result, the outermost layer stays in a liquid state even at temperatures way below freezing.
So far, scientists haven’t been able to decide which of these two theories is correct. Without a definitive answer at this point, it’s safe to say that both theories play a role in keeping ice slippery.
(13 votes, avg. 4.00 out of 5) 
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Tomorrow’s wonder must be about the leaning Tower of Pisa!
We think you’re pretty clever, Rahul! We’ll all have to check Wonderopolis tomorrow to see if your guess is correct, though!
I really liked today’s wonder! I was also wondering if ice could still be slippery after it was broken into pieces, or would the thin layer of liquid water not be there anymore?
That’s a GREAT question, Liddie! We think it would depend on the size of the broken up ice. For instance, if the pieces of ice were small, the surface area of all the broken ice (and their combined edges) might help distribute the thin layer of water. Those smaller pieces might actually provide some traction and make the ice less slippery than if it was a large, whole sheet of ice.
Wow! We haven’t seen any ice here this year. However, we have been talking about solids, liquids and gases in our class. This was a very interesting wonder. We are getting ready to talk about friction in science. Thanks for the introduction!
We’re glad today’s Wonder could help you with your studies about the states of matter AND friction, Mrs. Miller’s 2nd grade! Thank you for letting us know that and THANK YOU for visiting Wonderopolis!
I think you might be talking about the Leaning Tower of Pisa tomorrow! I can’t wait to find out if I’m right!
We can’t either, Tommy! A Wonder about the leaning Tower of Pisa would be so AWESOME!
Wow! That was a cool article. I wonder what’s next. One time when I went sledding, these two guys made a huge ramp. So they let me try it out and I went so high I actually went at least 15-20ft. It was so fun and I wasn’t hurt so that is the good thing. But ice is so cool and cold. I usually throw ice on the sidewalk. Sometimes it gets really heavy. Oh sorry, got to go. Bye.
Thanks for sharing your personal connection to this Wonder of the Day®, Austin! We’re certainly glad you weren’t hurt, either!
Thanks for the great wonder today. When wondering, we had thought that the smooth surface of ice caused less friction and made the surface of ice slippery. Now you have us thinking…Would ice be less slippery if there was no film of water on top?
That’s a GREAT question, Mrs. Smith’s Grade 2,3 class! We’re proud of you for WONDERing more about today’s Wonder of the Day®! You’ve got US WONDERing a bit more about ice and its slippery qualities now, too!
Wonderopolis is a cool website. We use it in my high school all the time. Thank you for making this website so we don’t have to do boring stuff.
Happy Thursday, Brady! We really appreciate your comment! It makes us happy to know that learners of ALL ages visit Wonderopolis every day and learn fun, new things! We think high school Wonder Friends ROCK!
I think today’s wonder of the day was awesome. You should have one about asteroids or outer space.
Guess what, Ivan? We have LOTS of Wonders about SPACE! You can check them out by visiting this link (it will take you to all the Wonders in our SPACE Category): http://wonderopolis.org/category/space/. Happy WONDERing and THANKS for visiting Wonderopolis!
Wow! this wonder of the day is freezing!!! (from Brevan)
Wow! That made me cold! (from Hannah)
The wonder of the day. Ice is slippery and water makes it slippery, too. (from Zackary)
That was a great video. I loved it. (from Emily)
That video was really good. (from Maia)
Hello from Wonderopolis, KF Dragons! We LOVED all of your comments about today’s CHILLY Wonder of the Day®! It sounds like you guys did some great WONDERing today…we’re proud of you!
Yeah, the leaning Tower of Pisa does sound cool, but I really want to learn about famous Inventors.
Have we got some Wonders we think you’ll enjoy, Kenneth! Check out these INVENTION-related past Wonders of the Day:
Wonder #99 – What Is a Patent? http://wonderopolis.org/wonder/what-is-a-patent/
Wonder #143 – Who Was George Washington Carver? http://wonderopolis.org/wonder/who-was-george-washington-carver/
Wonder #166 – Who Invented Basketball? http://wonderopolis.org/wonder/who-invented-basketball/
Wonder #396 – What Are Prosthetics? http://wonderopolis.org/wonder/what-are-prosthetics/
Happy WONDERing!
I never knew WHY ice floated. Thanks.
We’re glad you learned something COOL by exploring today’s Wonder, Isaias! Thanks for letting us know by leaving us this great comment!
That’s the reason I don’t like winter because I always slip on the ice!
YIKES! We hope you’re super careful when you’re out in the winter weather, Brigitte! We want all of our Wonder Friends to stay safe!
The best website ever.
Thanks so much for saying that, Brooke! We sure do appreciate it! You’re a GREAT Wonder Friend!
This video is so cool. I did the experiment on this. It was cool. There was ice on the road in my neighborhood I slid on it and fell and other kids did it, too. One dude slid on it like it was a skateboard. He did a really cool trick. I want to do that someday, but I don’t think I can.
Thanks so much for letting us know you did one of the activities from today’s Wonder and that you thought the video was cool, Aleia! We hope you and your friends in the neighborhood play safely around that ice…we don’t want you guys to get hurt!
Me and my mom and my brother went ice skating 1 year ago. Me and my dad and my sister want to an ice skating rink and raced a lot of good people. It was fun. I came in sixth place.
Way to go, Nolan! That is so AWESOME that you and your family have been ice skating and that you were even in a race! Thank you so much for sharing your story with us today!
That was cool music and that was pretty snow. I want to now where it came from!!! Can you tell me please?
We liked the music and scenery in the video for today’s Wonder, too, Ashlyn! Let’s use a clue to try to find out where the video was filmed. The title of the video is “Dutch Winter.” Where do you think it might have been filmed with the word “Dutch” in its title?
Dear Wonderopolis,
Awesome wonder! I think tomorrow’s wonder is about bugs.
XOXOXOXOXO,
Paige
Thanks for giving this Wonder “two thumbs up,” Paige! We think you ROCK!
Señora Waingort’s grade 2 class says:
Warning: ice is very slippery! Warning: ice can be thin.
How does water turn into ice?
We liked the scenery and the music in the video.
You’ve left us another AMAZING comment today, Señora Waingort’s grade 2 class! We can tell you guys did some AWESOME extra WONDERing about today’s Wonder, too! We also liked the scenery and the music in the video…we wish we could visit that place!
That was a good wonder for today, because today my 4th grade class was ice skating.
What a COOL coincidence, Susan! We hope you and your classmates had a WONDERful time ice skating! We like to go ice skating at a rink here in Wonderopolis, too…it’s FUN!
How do we upload a picture?
Hello, Susan! Thanks so much for visiting Wonderopolis today! The comment section of each of our Wonders of the Day® is only set up to allow for written information and links (not photos). We’re super careful about what links we allow our Wonder Friends to share, also, because we want all content on Wonderopolis to be safe for everyone to view and learn from!
Hi, this is Mukund from Mrs. Caplin’s class. I learned that a very thin layer of liquid exists on the outermost edge of ice. I also learned that 1 theory is that friction causes the liquid layer of water to form on ice. This is a perfect wonder of the day because we just finished electricity and started heat or thermal energy in school. Yesterday we learned that there is no such thing as cold because the atoms are molecules are just moving slower. I learned that water’s solid form (ice) is less dense than its liquid form. I think tomorrow’s wonder will be about the Leaning Tower of Pisa. This was an amazing wonder.
Well, we think this was an AMAZING comment, Mukund! You sure learned a LOT about ice by exploring today’s Wonder. We liked hearing all the interesting facts you found out about ice! We’ll have to wait and see what tomorrow’s Wonder will be about…we hope you are RIGHT!
What is ice.
Hi, Rashell! We’re so glad you visited Wonderopolis today and left us this great comment! Ice is frozen water. Ice is a solid and water is a liquid. You can learn more about the states of matter by visiting past Wonder of the Day® #276 – Does Matter Really Matter? Here is a link that will take you right to it: http://wonderopolis.org/wonder/does-matter-really-matter/. Happy WONDERing!
Wow! This wonder is amazing and I learned that Scientists have discovered that a very thin layer of liquid water exists at the outermost edge of ice though it is very cold. Mrs. Caplin’s class is learning about water being a solid, liquid, and a gas all through physical change which is what I connected this wonder to. I didn’t know that people had different theories to explain the presence of the thin water on the ice. Why didn’t it freeze like the other water that did turn to ice? I am thinking that tomorrow’s wonder will be about the Leaning Tower of Pisa because the leaning Tower of Pisa is leaning and is located in Italy. Thanks for a great wonder!
We’re so excited that you and your MC classmate, Mukund, were able to connect today’s Wonder to what you are learning in Mrs. Caplin’s class, Lynn! Way to go! Thank you for sharing all the COOL things you learned about ice today!
hey…wonderapolis… the music was werid…but… the video was nice…Have you ever been ice-skating before?
Yes, Marion, we have! It was super FUN! We can’t do any ice skating tricks yet, though, but we are practicing! Thanks for stopping by Wonderopolis today!
Hi, my name is Jack Triplett from Mrs. Caplins class. I thought the video for this wonder was really interesting because it never said anything, it just showed ice and points of views from ice. I learned that one of the reasons why ice is slippery is because there is a very thin layer of liquid water that exists at the outermost edge of ice even with ice that is extremely cold. I also learned that for years, scientists believed that this thin layer of liquid water was the resault of pressure being aplied to ice. Another fact that I learned was that the lower the density of the ice means that it’s melting temperature can be lowered by applying pressure. I will be sure to comment later.
WOW! You sure did learn a LOT about ice from this Wonder of the Day®, Jack…WAY TO GO! Thank you for sharing your COOL comment with us today!
Hey, this is James from Mrs.Caplin’s class. I had never wondered why ice was so slippery and didn’t know there were so many theories for it. I think that the ice being slippery has nothing to do with friction or pressure, I think it is just because of the water on top. I liked the music in the video but it didn’t really explain anything about why ice was slippery. I was thinking about how the first computer was made and what it did. So I was wondering if you had any facts about it or could do a wonder on it. Next time I go ice skating I will think about the thin layer of water on top of the ice. I think that the best vocabulary word I could use in my writing would have to be treacherous. I predict that tommorow’s wonder will be about The Leaning Tower of Pisa. Finally, I wanted to thank you for another wonderful and fabulous wonder. Bye.
We think your comment is pretty WONDERful and fabulous, too, James! Thanks for sharing it with us today! Sometimes the videos we choose for the Wonder of the Day® might explain the Wonder a little better, but sometimes they just add something “extra” to the Wonder experience! We think the video for this Wonder did just that!
Hi! This is McKenna from Mrs. Caplin’s class. This was a phenomenal WONDER, that taught me so many new facts. It also really related to what we are doing in science. We are learning how molecules in a solid vibrate, how molecules in a liquid flow, and how molecules in a gas are just going crazy. Anyway this new knowledge really helped me understand this concept more. Some of the new facts I learned were that scientists have discovered a very thin layer of liquid that exists on the outermost layer of ice, even though it is very cold. I also learned that if you just stand on the ice, you are not producing any signs of friction. The last thing I learned was that scientists aren’t even sure what the actual theory is behind slippery ice. Lastly I have just a few questions. Are there only to theories to why is ice slippery? Why doesn’t the thin layer of water on the outer part of the ice freeze? How cold is the liquid on the outermost part of the ice? Well, thanks for a fantastic WONDER of the day!
We think it’s super COOL that you and your MC classmates are able to combine what you are learning in science with what you learned from this Wonder of the Day®, McKenna! We love it when we hear awesome things like that! You asked a lot of great questions, too. We’ll all have to do a bit more WONDERing about them to find the answers!
How does the cold freeze the water in the winter? Is ice solid the whole way through or is it one layer of ice and water under?
Those are GREAT questions, Everett! To learn more about the states of matter, including ice (solid) and water (liquid), check out Wonder of the Day® #276 – Does Matter Really Matter? http://wonderopolis.org/wonder/does-matter-really-matter/. Happy WONDERing!
Wow that is very surprising that there’s a thin layer inside ice that contains liquid!! I never thought there could be liquid in a solid and the solid can still stay strong, but one time I went on a frozen creek with some friends and it cracked!! Luckily, the water didn’t even go up to our knees, so it wasn’t a bad experience. This is so cool that you posted this wonder because in Science (Mrs. Caplin’s class, that is) we learned about liquid, solid and gas and also physical changes, so I had a little background knowledge that helped me out with this wonder. We also learned about energy and friction in science, and friction is one of your vocab words for this wonder. Hey I was just wondering about dry ice and do you know what dry ice is??? Is it even an ice???
I learned a lot so thanks a lot!!!
We’re so happy you had background knowledge about this Wonder before you explored it, Leah! COOL! Did you know there is a Wonder of the Day® about Dry Ice? It’s past Wonder #255 – Is Dry Ice Really Dry? You can check it out by clicking on this link: http://wonderopolis.org/wonder/is-dry-ice-really-dry/. Happy WONDERing!
I thought that this wonder was outstanding! I thought that the video was really interesting how they didn’t tell us any facts, but they showed multitudes of people ice skating. I didn’t know that what makes ice slippery is WATER! When I read it, I was so surprised that the ingredient to slippery is WATER! I think that this wonder is especially amazing because right know in science, we are learning about thermal energy and the states of matter changing. This wonder gave some more information on that topic and Mrs. Caplin said that she thought that you guys made this wonder right at the right time! A few nights ago, I helped my sister study for a science test. One of her vocabulary words was density, and I didn’t understand the meaning. In this wonder, you used the word density and said that the lower density of ice means that its melting temperature can be lowered by applying pressure. I understand that more. Thanks for the PHENOMENAL WONDER!!!
We think you “MC” students ROCK, Jack! Thanks for letting us know you guys are studying related subjects in science and that you learned the meaning of “density” by exploring this Wonder! Now you can help your sister understand a little more, too!
Ice Is Awesome! Know That I Know This Stuff. Ice Is Better.
Thanks, Until Then…
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Thanks for sharing your feelings about ice with us today, Joaquin! We appreciate your comment and your enthusiasm for Wonderopolis!
Woooooooooww ~ I really like this picture <3 it’s pretty!
Thanks for letting us know you liked the picture for today’s Wonder, Peanut!
Could you tell how ants get a new queen when the queen dies?
That’s a GREAT idea for a future Wonder of the Day®, Abigail Rae! Thank you for suggesting it! Did you know there is a past Wonder about ANTS? It’s Wonder #258 – Why Do Ants Think They’re Invited To Picnics? Here is a link that will take you right to it: http://wonderopolis.org/wonder/why-do-ants-think-theyre-invited-to-picnics/. Happy WONDERing!
Hello, wonderopolis! I loved today’s wonder. One day we went to are friend’s house and when we got back the floor was slippery. We were sliding back to our house. My mom stayed in the grass my brother and dad could just slide down. I kept falling. Bye, wonderopolis, have a nice day!
Thanks for sharing such a COOL story about ice with everyone in Wonderopolis today, Kayla! It’s awesome that you have a fun family memory like that!
I have not seen snow this year. I love wonderopolis.
The feeling is WONDERfully mutual, Kimberly! Thanks for being such an AWESOME Wonder Friend and visiting this Wonder of the Day®! We hope you had lots of fun learning some new things about ice!
I think it’s slick because it’s a little too slippery or slick.
Hello, Jen! Thanks so much for visiting Wonderopolis and for sharing your thoughts about why ice is slippery!
I picked this one because I really have always wondered that and now I know, and if someone asks me about that, I can tell them. It’s always important to know things when people ask, and it’s not a bad thing, but anyway thanks wonderopolis for being here, and answering all my wonders…
It makes us really happy to know you liked this Wonder of the Day® about ice so much, Macy! We like learning in Wonderopolis and we’re glad you do, too! Thanks for leaving us this great comment to let us know!
Hey, why don’t you guys talk in the videos?
That’s a GREAT question, Wonder Friend! We don’t make all the videos we use for the Wonders of the Day®. Most of them are awesome videos that other people make, and we pick them to accompany the Wonders because they either help explain the Wonder better, or they show something fun or interesting about the Wonder topic. Sometimes the videos we pick just have musical backgrounds. Thanks for visiting this Wonder and leaving us this comment!
I know why ice is slippery, it’s because of the water.
That’s what a lot of scientists think, Wonder Friend! Thank you for checking out this past Wonder today!
Awesome wonder! I never knew why ice was slippery!☺☻☺☻☺☻☺☻☺☻☺☻☺☻☺☻☺☻☺☻☺☻☺☻
We’re so excited you learned something new, Jake!!