“Dear Scouter Atom,
Last week, I visited Clear Lake in Manitoba. The ice was completely clear! I could see all the way to the bottom. Why does this happen?
Yours in Scouting,
Dear Scouter John,
What a cool experience! Some hikers saw something similar in Slovakia in 2014.
In short – no snow, no wind and cool temperatures.
Think about the ice cubes that you make in your freezer at home. Most of the time, these ice cubes aren’t clear all the way through. Instead, there is a cloudy centre. This cloudy centre is caused by tiny particles that are dissolved in the water that comes out of your tap. Think about the last time you filled a glass straight from the tap, only to notice that the water is cloudy. If you let that glass sit for a few minutes, the water will become clearer as the tiny air bubbles dissipate.
Everything freezes from the outside in. If you pull an ice cube tray out of the freezer before the cubes are fully frozen, what do you notice? The edges might be frozen, but the inside is still liquid. Water that is free of teeny tiny particles freezes first, on the edges of the ice cube, forcing water containing impurities and air bubbles to the centre. Air bubbles are a common culprit when it comes to cloudy ice. On the lake, wind blowing across the surface adds a lot of air to the water. When the water freezes, the ice is cloudy. Snow also introduces impurities to the ice. When snow mixes with water, the ice forms with a white finish.
Lakes freeze from the top down. The top layer of the water is the first to freeze. Because ice is less dense than water, the ice floats on the top of the lake. Slowly but surely, the ice will cool the water directly below it, causing ice crystals to form below the surface.
Make clear ice cubes at home!:
- Get a hard-sided, insulated cooler that will fit in your freezer.
- Fill the cooler about three quarters of the way with clean water to create a clear ice block. Remember that the ice will expand as it freezes, so don’t fill the cooler all the way to the top.
- If you want an easy way to divide the big cooler-sized block into smaller cubes, you will need to divide up the space. Hard-sided plastic containers, placed upside-down in the cooler, are good for this.
- Put the cooler in the freezer without the lid.
- After about twelve hours, it’s time to check the ice. Remember that the water will freeze from top-to-bottom, so the air bubbles have been pushed to the bottom of the cooler. If you’ve timed it right, you can get the ice out just before the cloud of bubbles is trapped at the bottom of your block of ice.
- Remove the cooler, and let it sit long enough that the ice melts a little – about fifteen minutes. Then flip it over and let the ice slide out.
- Break apart your ice blocks into smaller chunks.
- Enjoy a nice, cool drink, and keep it colder longer using your clear ice cubes.
Until next time,
Scouter Atom is a Colony Scouter with a passion for STEM adventures. There is no question too small, no question too large – if you have a question, Scouter Atom has an answer. Send your questions to firstname.lastname@example.org.