there's baking soda (or sodium bi-carbonate) and and baking power for for numerous baking applications (if there's a cooking use, please call me out on that!). baking soda creates porosity via reaction with an acid, which generates carbon dioxide (the heat then increases that initial, induced unit volume). however, baking powder (as it is so marketed, "double-reacting") creates that initial porosity via carbon dioxide generation via acid AND heat.
so, my question is this: is there any leavening agent that provisions this initial porosity via ONLY heat alone? in case anyone is wondering, please forgo any kind of natural or "sourdough"-type approach to solving this question.