The brewing part of the coffee-making process isn’t about chemical change – rather, it’s about extracting compounds from the roasted coffee beans. How well different molecules can be extracted depends on their solubilities, which in turn depends on a property known as polarity. Different types of atoms exert more of a ‘pull’ on the electrons in chemical bonds than others; oxygen exerts more of a pull on bonding electrons than carbon, for instance. A bond between a carbon and oxygen atom is what we would refer to as a polar bond, as the bonding electrons are pulled closer to the oxygen atom, giving it a slight negative charge.