Hi Peter

Firstly, congratulations on producing a fantastic book. All my family (wife, and two high school children) are reading and enjoying.

Something that we questioned is on Page 26, where it states that 'At the same pressure, a gas needs more space than a liquid (and a liquid needs more space than a solid)'

If thats correct then why do frozen pipes crack ?

I'm pleased you and your family enjoyed the book! It's a vey good question - the answer is that water behaves rather strangely. Unlike most solids, ice has more space between its molecules compared to its liquid form, water. It's because of the shape of water molecules, which like to lock themselves together in a little "honeycomb-like" structure. That's why ice floats on water, and why ice expands. But water is a weird exception (that happens to be commonplace to us) - most solids are more dense and smaller compared to their liquid form, just as the liquid form is more dense and smaller compared to the gaseous form. For more information, check out this website: http://www.iapws.org/faq1/freeze.htm

I hope this helps!