Periodic Table of the Elements App for iPad
'This is a standard periodic table of the elements - a necessity for anyone interested in or even exposed chemistry. However, the version differs in that instead of cramming all the information for an element into one little square, you can select a chemical attribute and have the entire chart color coded to plainly show how the different elements vary with regard to the selected trait.
You can select
1. Atomic Number
2. Chemical Family
5. Melting Point
6. Boiling Point
7. State (Solid, Liquid or Gas)
When State is selected you can change the temperature using a slider control to see the states of the elements at the temperature you select.'
This is a free app