The reaction between citric acid and baking soda (sodium bicarbonate) is an example of an endothermic reaction. This means that the reaction absorbs heat from its surroundings, causing the temperature to decrease.

Here's a breakdown:

* Chemical reaction: Citric acid (H₃C₆H₅O₇) reacts with sodium bicarbonate (NaHCO₃) to produce sodium citrate (Na₃C₆H₅O₇), water (H₂O), and carbon dioxide (CO₂).

* Heat absorption: The reaction requires energy to break the bonds in the reactants (citric acid and baking soda) and form new bonds in the products. This energy is absorbed from the surroundings, causing the temperature to drop.

Other examples of endothermic reactions:

* Dissolving ammonium chloride in water.

* Photosynthesis in plants.

* Melting ice.

Note: The decrease in temperature is not always noticeable, especially if the reaction is happening in a large volume of water or if the reaction is happening quickly.