This paper explains students' ideas about food as a scientific concept that a questionnaire was administered to 40 secondary level students. The findings have been shown that in students' mind food was essential for living, growth and supplying energy. Also students could accept the idea of food could be in liquid form. Students' understanding of the biological concept of food was anthropocentric and not applied across living organisms in heterotrophs (animals) or autotrophs (plants) as a whole. Many students confused water food or not. Mostly water not accepted as a food because of it does not yield energy for organisms. It looks a vital point that to emphasizing food as any substance (in solid or liquid state), can obtainable energy during respiration during alive activity.