Relevant Resource questions :

Concepts demonstrated :

• Change of state.

Relates to 3D Phase Diagram.

Equipment needed :

• large block of ice made from de-ionised water (boiled will do)
• bricks or wood to mount the ice
• 2 lead balls and a connecting wire

• A large block is mounted on top of blocks as shown.
• A wire with two masses attached is hung over the block of ice.

Accessories (ie posters etc) :

Physics involved

The weight of the lead balls does work which causes the ice to melt at the point of the wire. As the ice melts and the wire passes through the ice re-freezes.

How to use the Demonstration :

• Set up the demonstration at the start of a lecture and ask students what they think will happen.
• Leave the demonstration running and hopefully they will forget about it until suddenly when the wire has passed completely through the ice there is a crash as the balls drop to the table.
• Show that this is only a function of pressure i.e. no thermal conduction effect from the wire. The pressure relates to the phase transition: it is independent of the wires.

• Ice skating rink. If the ice is too cold, it gets slower (for the skaters).

• Put in a cold box so that the ambient temperature is the same as the temperature of the ice (Tice).
• Try with dry ice - now it would be a thermal effect.

• There is a good paper on this - obtain from Brian McInnes.