Lots of Ice

Most recent answer: 10/22/2007

Q:
Are there different kinds of ice? What substances melt ice the fastest?
- Peter (age 12)
Trexler Middle School, Allentown, PA
A:
Ice is just frozen water. But when you freeze water, different things could happen.

Water from different places have different minerals in it. That’s why different ice tastes different to you.

Another difference is the density of the ice. When water freezes in a freezer, a lot of air is frozen along with it. But there are also glaciers, huge ice sheets hundreds of feet thick. They are so heavy that a lot of that extra air has been pressed out. That makes the glacial ice a little bit heavier than the ice from your freezer.

The biggest difference from one piece of ice to another is it’s structure. Ice is a crystal. A crystal is the name used when atoms and molecules are formed into an organized shape. A good example is a brick building. The bricks are laid so that they are in a pattern. However, when a crystal (like ice) forms, it never works perfectly. Every crystal has many defects in it. When you let the ice take a long time to freeze, it will have fewer defects.

As for the last part of your question, anything warmer than 0 degrees C can melt ice. The warmer, the better. Another way to melt ice is to cover it in salt. Regular water freezes at 32 Fahrenheit, but salt water freezes at a much lower temperature. When you put salt on top of ice, the salt causes the ice to melt since the salty water finds it too warm to remain frozen. This is why they put salt on the roads when it snows. The salt melts the ice (unless it’s colder than about 0 Fahrenheit).

Its an interesting fact that when you mix ice with salt in this way, causing the ice to melt, the remaining ice and salt-water mixture actually gets colder. This is because heat is required to melt the ice that is touching the salt, and this heat is drawn out of the surrounding ice. If you take a bucket of crushed ice and dump a bunch of salt into it (and stir a bit) the remaining mixture will be much colder that it started out being. Before freezers this was a common way to get temperatures cold enough to make ice-cream.

Adam

(published on 10/22/2007)