Only one of my bottles of water froze

This week, why only one bottle of water froze while others remained liquid; do hot drinks cool you down? What's phlegm and is it safe to swallow? Is human body temperature changing? How did the NASA student intern discover an exoplanet? Are fizzy drinks safe for diverticular disease? And what's the ideal healthy diet for a human? Join Dr Chris and Kieno Kammies to find out... Like this podcast? Please help us by supporting the Naked Scientists