Baking soda does not lower the temperature of water — instead it raises the temperature slightly, due to the chemical reaction that takes place. Baking soda and water creates an exothermic chemical reaction, which means the binding energy of the chemical bonds has leftover energy that is released to warm the water.
Endothermic chemical reactions require additional energy in order to make the reaction go. These reactions take place at a much slower rate than exothermic reactions do. The temperature must be raised manually in order to make the molecules react. Evaporation is one type of endothermic reaction. It requires heat in order to create vapors.