f Cooking and carbon dioxide The purpose of baking powder or soda in cooking is to produce tiny bubbles of carbon dioxide This expands the pastry cake or dough making it light and pleasant to eat Yeast cells do the same thing in bread making though this takes longer Baking powder or sodium bicarbonate NHCO3 reacts with an acid such as lactic acid from sour milk to produce carbon dioxide Commercial baking powders often contain a solid acid which only reacts with the sodium bicarbonate when moist i Put baking powder into water Note whether carbon dioxide gas forms Note whether carbon dioxide forms when you put sodium bicarbonate into water Add baking powder in a testtube with vinegar or lemon juice acetic acid Note whether carbon dioxide forms ii Make a sugar solution and half fill a jar with this solution Add a spoonful of yeast and leave to stand for 2 days Construct a bubbler to fit on the top of the jar Note whether the yeast forms a gas Note whether carbon dioxide gas collects in the upper part of the jar