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Why do cakes rise when they are baked?

A cake rising as it bakesA cake rising as it bakesTo make a cake, you add bicarbonate of soda to the cake mixture. It reacts with acidic ingredients, such as lemon juice, milk, honey or brown sugar, that are also in the mixture. As a result of this chemical reaction, carbon dioxide is released as a gas. The gas expands, forming bubbles in the cake mixture. This gives the cake extra volume as it bakes in the oven: it rises. The resulting texture is (or should be) light and fluffy. The chemical equation for this reaction is this: 2NaHCO3 Na2CO3 + CO2 + H2O

Time-lapse footage of a cake rising

Baking soda mixed with vinegar produces bubblesBaking soda mixed with vinegar produces bubblesBicarbonate of soda (sodium bicarbonate, NaHCO3)—also known as baking soda, or, more correctly, sodium hydrogen carbonate—is a salt composed of sodium ions and bicarbonate ions. Described as a leavening agent (a substance used in doughs or batters to lighten and soften them), it often appears as a fine, white powder.

In 1846, two New York bakers, John Dwight and Austin Church, established the first factory to produce bicarbonate of soda from combining sodium carbonate with carbon dioxide.

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