Anhydrous sodium carbonate (`Na_2CO_3` ), at ambient temperature, is hygroscopic, meaning that it absorbs water if it is exposed to air. Sodium carbonate has a melting point of 851^o C.
When sodium carbonate is heated, it looses carbon dioxide and the resulted product is suitable in baking. The texture of baked food, which has baking soda, among other components, becomes fluffy and tender, because of the carbon dioxide air bubbles. It must be stressed that sodium bicarbonate used for baking purposes, needs to be mixed with acidic materials to avoid traumatic digestion, occuring when `HCl ` found in stomach reacts with `Na_2CO_3` , to release `CO_2.`
The chemical reaction describing the release of carbon dioxide, when sodium carbonate is heated, is given below:
`2NaHCO_3 -> Na_2CO3 + H_2O + CO_2`