1.   Thus, without any change in the composition across the boundary, the phase change produces a temporarily layered mantle.

2.   Under these conditions many solids undergo phase changes, and the nature of the accompanying changes in structure can be studied.

3.   These samples might then exhibit almost perfect first order phase changes at the melting temperature.

4.   The enthalpy changes that occur during a chemical reaction or phase change vary depending on temperature, pressure and the physical states of the substances involved.

5.   The temperature at which a phase change occurs is called the transition temperature.

6.   The elbows in the lines indicate phase changes-melting or boiling --of the metals.

7.   Although the various models defy any simple classification, for convenience we will consider them under the headings of thermal, phase change and mechanical models.

8.   Such phase changes occur when minerals adopt different atomic configurations as temperatures and pressures change.