Water boils at 100°C at sea level. If the water in this experiment did not boil at 100°C, what could be the reason?

One reason could be that the water in this experiment, didn’t boil, but instead became a “chemical reaction” from atmospheric pressure which is normal.

While heating two different samples, of
sea level water it decides on a temperature of 102°C and the other boils at 99.2°C. Basically calculating of the percent error.