While the freezing point of a particular chemical is often determined empirically (meaning by actually testing) the chemistry of a particular chemical is often used to establish different trends within related chemicals. For example, your question regarding the freezing point of water versus different types of alcohols. Water with the molecular formula of H₂O can be compared to methanol with a molecular formula of CH₃₂CH₂OH. As the number of CH groups increases we would expect the freezing point to decrease.