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Activity 1

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You are watching: Why does an ice cube melt when you hold it in your hand

Try the activity!

Heat: You can do this activity using a baggie with a handful of ice inside, or just place a cube of ice in your palm. Heat from your hand will warm the bottom of the ice forming a small puddle of melted water just like a subglacial lake.

Topography: The water as it melts collects in the cup shape in the palm of your hand. Try to move the ice cube away from the center of your palm to see if you can get the water to collect on another part of your hand. Can"t do it? That"s because water will collect in low areas. The palm of your hand is just like a lake bed, a depression or low spot in the land surface. Scientists call the shape of the Earth"s surface its topography.

Pressure: You need an ice cube, a piece of wire and a flat surface. Pull down hard on both ends of the wire applying pressure to pull the wire through the ice cube. Be patient this takes a minute. See how the wire makes a groove in the ice. The wire is not cutting the ice, the pressure you apply is melting the ice just under the surface of the wire. This is like the glacial ice pressure pushing down over the lakes.


Lakes & Topography

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Look the ice resting in my hand. The heat from my hand is causing the ice to melt (Click on the image to learn how). My hand acts much like the heat that is contained in the hot center of the Earth. The ice cube represents an ice sheet. As an ice sheet rests on the surface of the continent the ice is warmed by the heat rising from the interior of the Earth. Once heat transfers to the Earth surface, the ice sheet acts like a thick insolating blanket holding in the heat. This adds to the melting. Once the water melts it collects in low area in the Earth surface. Go to "Try this activity" and test some of this yourself.

Pressure

In addition to the heat from the center of the Earth, there is pressure being added to the bottom layers of the ice sheet from the large amount of ice pressing down on top of it. The thicker the ice sheet the more pressure that is pushing down on the ice at the bottom causing melting at the bottom of the ice sheet. Why? Because the melting point of ice drops when the pressure is increased.

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How does this work? Think of it this way, if you were going to make a snowman you would start by rolling snow together, pressing together the individual flakes. As the snow is pressed together, the pressure will lower the melting point of the snow, causing it to melt together. If this didn"t happen you would need glue to hold your snowman together!

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That sounds messy!


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You Can Melt Ice!

Let"s see how much pressure you can apply! Try this Pressure activity to see if you can melt ice using pressure! The pressure you will be applying is just like the heavy pressure being applied from the thick layers of ice that lie on top of the Antarctic continent. Once the water forms under the ice it will collect in low areas in the topography to form subglacial lakes.




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