During last week’s Cast YOUR Vote, students voted to decide what topic we should learn about this week. Thank you to all who voted! Your top choice was “ice”. Ice has definitely been on our minds lately as we are making the switch from paddling a canoe in the lakes to walking on the lakes. It has been amazing to witness the top of the lakes change from liquid to solid. We did some research about ice and how it forms on the lakes. I’ll share with you what we learned below.
What is ice?
Ice is frozen water. Did you know that all liquids have a boiling point and a freezing point? When water boils at 100 °C (212 °F) it turns into steam. When it is cooled to 0 °C (32 °F) it freezes and turns into ice. When the outside temperature falls below the freezing point of water, lakes and rivers eventually freeze.
Do you live in a place where the lakes freeze in the winter?
As the water gets colder, the molecules of water lose their energy and move more slowly. When the molecules move more slowly, it is easier for them to hook on to each other. When enough of the molecules hook together, they form a pattern that looks like a bunch of hexagons locked together. That is ice. Ice is hard and stiff because the molecules are all locked into place.
How does ice form on lakes?
Only the top layer of lakes and rivers freeze. Underneath the frozen upper layer, the water remains liquid and does not freeze. Water is one of Earth’s most interesting substances, because as water freezes, ice forms on top rather than on the bottom. If water were like other substances, ice would form on the bottom of lakes and ponds because water would become more dense and sink as it cools.
The reason why ice forms on the top of lakes and ponds is that once water cools below 4 °C (39 °F), it becomes lighter and less dense the more it cools. This means that water expands as it freezes into ice. This makes ice lighter and less dense than the water below it, allowing ice to float on top of the water, rather than sink to the bottom.
We sure are glad that the ice forms on top of lakes instead of the bottom. That means we can walk on top of the ice while fish can still swim in the water below.
What would happen to fish if ice formed on the bottom of lakes instead of the top?
Why does ice make noise on lakes?
During the past month, Dave and I have heard all sorts of interesting noises coming from the lakes as they freeze. We have heard pops and groans almost like sounds a whale would make. Frozen lakes make the most noise during major changes in temperature. The ice expands or contracts when the temperature changes. This causes cracks to form in the ice. It is the cracking of the ice surface that makes the interesting noises we have heard. The sheet of ice on a lake is like a giant membrane that the sound travels across. This also explains why we have heard the most noise from the lake in the morning and evening, as the temperature rises or drops.
Have you ever heard ice making noise? What did it sound like?
Click here to hear the sound of ice on a lake:
Student Response Worksheets