Why will cookies be slighty lighter than the batter used to make them?

Cookies are slightly lighter than the batter used to make them for a few reasons:

* Evaporation of Water: During baking, water in the batter evaporates. This creates steam, which escapes the oven, leaving behind a lighter cookie.

* Expansion of Air: As the batter heats up, air trapped within it expands. This expansion contributes to the rising and lightness of the cookie.

* Chemical Leavening Agents: Baking soda and baking powder, if used in the recipe, release carbon dioxide gas during baking, which also creates air pockets and contributes to the airy texture.

* Sugar Caramelization: Sugar in the batter caramelizes during baking. This process forms a slightly lighter and more porous structure in the cookie.

Overall, the combination of these factors leads to a final cookie that is lighter than the original batter. This lightness is a desirable characteristic of cookies, as it makes them more appealing to eat.