As you might already know, ice is less dense than water because of the effects of hydrogen bonding. This is why ice floats on water and also why sealed containers often expand in the freezer.
In this simple demonstration we're going to observe what happens when ice melts. Now I know what you're thinking... "I already know what happens!" But fear not: there's more in store for you than just watching ice melt. In fact, what we're about to do has some important real world significance. Since at least the beginning of the 20th century, sea levels have been rising due to climate change and the melting of earth's glaciers and ice sheets. But as we're about to see, the answer to the question, "Why are sea levels rising?" isn't quite as simple as it may seem.
Place the measuring cup in a warm area that can afford to get a little wet. We did ours on the kitchen counter, but the sink is also a good place. This experiment also works great outside.
Place several ice cubes in the measuring cup. A good rule of thumb is to fill about 1/3 of the measuring cup with ice. (Note: make sure you're using regular ice cubes and not crushed ice. This experiment works best with larger-sized cubes.)
Pour enough water over the ice cubes until they're all floating and no longer touching the bottom of the measuring cup. Some of the tops of the ice cubes should be sticking out of the water, just like glaciers stick out of the ocean.
Record the water level by using the lines on the measuring cup, trying to be as precise as possible. It might be helpful to add a little extra water in order to reach one of the lines.
Now, after your "sea level" has been recorded, we have to wait for the ice to melt. This shouldn't take too long, but make sure not to forget about your experiment, otherwise the water might evaporate too much.
Once the ice has melted completely, measure the water level once again, again trying to be as precise as possible. Did the water level rise, stay the same, or fall? Based on this result, can you figure out why earth's sea levels are rising?
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