Monday, 6 January 2014

Cut the Ice



EQUIPMENTS:
  1. Thin metal wires such as copper wires
  2. An ice cube
  3. Wire cutters or scissors
  4. Even number of metal washers or nuts (Maybe you can use 10 of those)
  5. A wood block or a tall can
  6. Modeling clay


INSTRUCTIONS:
  1. At first, cut a piece of copper wire which should be about the height of the can.
  2. Now tie the same amount of metal washers or nuts on each end of the copper wire.
  3. After that place the ice cube on top of the can.
  4. Then put some modeling clay around the ice cube so that the ice cube doesn’t slide off the top of the can.
  5. Now position the wire across the center of the ice cube so that the metal washers or nuts can hang off the edge of the can.
  6. Finally wait and observe. It may take about 10 to 15 minutes for the experiment/project to be finished.


RESULTS:

After a while (which should probably be about 10 to 15 minutes depending on many things), the wire should cut through the ice cube completely.


EXPLANATIONS:

The washers or the nuts in the experiment weigh the wire down. So the wire presses the surface of the ice cube. The parts of the ice cube which are directly pressed on by the wire melt at a faster rate than the rest of the ice cube. This happens because melting temperatures are dependent on pressure.

Usually, the melting point of ice is imposed by atmospheric pressure. Atmospheric pressure is the pressure that the air around us exerts on everything. When ice is placed under increased pressure it can melt at a lower temperature then it would at atmospheric pressure. So in the same way, by increasing pressure at certain parts of the ice cube, the wire is able to cut through the ice cube very easily.

This experiment/project works with ice because of a unique attribute of water. For most materials, the melting point actually increases with pressure. That means the more pressure you give a it, the higher the temperature required to melt it. But the density of ice is less than the water. So that’s why the melting point of ice decreases with pressure.


MORE EXPLANATIONS:

The same principle also applies on ice-skating which is demonstrated here in this experiment/project. When a person skates on ice, his/her weight is distributed on the blade, which applies pressure on the ice. The ice directly below the blade of the skate tends to melt down more quickly than the rest of the icy surface. This is what allows the ice-skater to move across the icy surface.


MORE EXPERIMENTS FOR YOU:
  1. Use string instead of wire which is not a good heat conductor.
  2. Try adding salt on the ice cube and do the same experiment again using copper wire once and string on the second time.

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