Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Model of a solid using students

Class practical

Apparatus and materials

Students

Health & Safety and Technical notes


Some laboratories may not have sufficient space to do this safely but a school hall could be used.

 

Procedure


students blocked together

a The students sit or stand in a regular array with arms stretched out to hold the shoulders of neighbours. 

b They should start at 'absolute zero' and they should be told to 'warm up' by vibrating to and fro. 
 
c If the model is allowed to go to higher and higher 'temperatures', the solid will eventually 'melt' as the crystal comes to pieces. 
 
d If a model of a liquid is needed, students should stand close together with arms folded, moving about as a fluid crowd. 


Teaching notes


1 There are occasions when the mood of a class makes this activity worth trying. If it can be done, it is useful because it is unforgettable! 

2 The full story of heating a solid is more complicated than the simple one of just making the amplitude grow as you warm up the model atoms, because there is a quantum restriction on the way in which an atom can carry vibrational energy. Atoms must carry energy in quanta. The restriction does not make itself felt in ordinary measurements, such as thermal capacity, at room temperature. However, at low temperatures, when the atoms are 'poor in thermal energy', the currency restrictions of quantum rules make themselves felt and specific heats drop to unexpectedly low values. This behaviour could not be explained on classical theory and itself helped to point to the quantum restrictions. 
 
This experiment was safety-checked in August 2007