Cake and other bakery products like bread etc are expected to become fluffy and soft. So during the preparation of such food items, baking powder is one of the most important ingredient added to the item.

So when the batter of the cake is heated, the baking powder present in the batter of the cake gets decomposed to form sodium carbonate, water, and carbon dioxide gas are given off. The pore present in the cake represents the location from the gas is liberated. So the main substance which causes effervescence is baking soda.

The reaction is given as:

2NaHCO₃→ Na₂CO₃ + H₂O + CO₂