A couple of non medical-related questions

These are just 2 questions which I have been wondering recently.


Why does salt melt ice?
Water and ice are at equilibrium at 0°c, adding solute to the system will disrupt this equilibrium. They dissolve into the water and do not pack uniformly into a solid, so the rate of freezing decreases, along with the melting point of ice. Any solute could be used, but salt is used on roads in icy conditions because it is cheap and readily available.


How is coffee decaffeinated?- (My Dad drinks decaf coffee as otherwise he gets heart palpitations)
Coffee is decaffeinated using 2 main methods: Water extraction and supercritical carbon dioxide extraction. Water extraction involves soaking the beans in hot water and passing this over hot charcoal before restoring the flavour by soaking the beans in this water again. Supercritical carbon dioxide involves heating CO_{2 under high pressure, forming a supercritical fluid which is like gas and liquid, when forced through coffee beans this absorbs up to 99% of the caffeine as it is gas-like and can penetrate deeply into the beans. Caffeine extracted using these methods can be used for soft drinks and medicines.}
However caffeine extraction is expensive and loss of some flavour is common. So as an alternative, there is potential to inactivate the gene in tea and coffee plants which codes for the caffeine synthase, which catalyses the synthesis of caffeine. 
Well now I know!