Students are told that baking powder is a mixture of three ingredients (baking soda, cream of tartar, and cornstarch) and that two of these ingredients react to produce a gas when water is added.

When using white vinegar instead of cream of tartar, follow the same ratios as you would for lemon juice. Unlike the other entries on this list, baking powder works best as a cream of tartar ...

You can make your own baking powder by combining 15ml/1tbsp bicarbonate of soda with 30ml/2tbsp cream of tartar. Measure carefully as too much or too little can upset a recipe’s balance.