Yes, the measured pH of orange juice will be
different at different temperatures. In fact,
the measured pH of any solution will be different
at different temperatures! pH refers to the
number of hydrogen ions floating around in a
solution--the more hydrogen ions, the more acidic
a solution is and the lower the pH. These
hydrogen ions come from the breaking or
disassociation of water: H2O breaks
into one hydrogen ion, H+, and one
hydroxide ion, OH-. The higher the
temperature, the more water disassociates.
However, it's important to note that since the
pH always depends on temperature, you can really
only compare the pHs of different solutions if you
measure them at the same temperature. For example,
the pH of pure water is about 7 at room
temperature, but if you heat it up to almost
boiling (100 degrees C or 212 degrees F) the pH
drops to 6.14. Also, the pH of pure water is
always defined as the "neutral" pH at a given
temperature, so a pH of 7 is only neutral at room
temperature. At 100 degrees C, a pH of 6.14 is
neutral! Therefore, while the pH of hot orange
juice might be lower than the pH of
room-temperature orange juice, if you compare the
pH values relative to pure water at the same
temperature the hot orange juice might not
actually be more acidic.
Hope this helps!
Click Here to return to the search form.