Originally Posted by sternwachter
Actually, none of it is converted into heat. The heat comes from the breaking of chemical bonds and does not affect the mass of the compounds involved (except in nuclear reactions, which we are not talking about here). The Law of Conservation of Matter states that mass IS conserved in a chemical reaction, which is what happens when we "burn" food for fuel. The mass of the food you eat, plus the mass of the oxygen you breathe, and the water you drink will equal EXACTLY the mass of the waste, CO2, sweat and urine that you produce.
Yeah I remember chemistry now the equations we did where you have a pile of stuff at one end and youve to work out what comes out, its always exactly the same. Matter is enegry tho E=MC^2 but thats nuclear stuff....