A didactic question publish in The Physics Teacher (http://tpt.aapt.org/resource/1/phteah/v41/i1/p8_s1) asks which will melt more ice: 100g of metal at 100C or 100g of wood at 100C. (The particular metal is not specified. I have paraphrased the question.)
The solution given is that the wood will melt more ice because it has a higher specific heat capacity, but no explanation is given for why wood has the higher heat capacity.
Is there a heuristic that would reliably give you this information? Clearly, the specific heat capacity depends on the number of degrees of freedom per gram of material. Does the wood have a higher heat capacity simply because it is composed mostly of lighter elements? Are there other important considerations for an order-of-magnitude estimate?
The wikipedia article is good (http://en.wikipedia.org/wiki/Heat_capacity) and has tables of specific heats, including both metals and wood. I didn't see something there that completely answers this question, though.