<P> Test tubes are convenient containers for heating small amounts of liquids or solids with a Bunsen burner or alcohol burner . The tube is usually held by its neck with a clamp or tongs . By tilting the tube, the bottom can be heated to hundreds of degrees in the flame, while the neck remains relatively cool, possibly allowing vapours to condense on its walls . A boiling tube is a large test tube intended specifically for boiling liquids . </P> <P> A test tube filled with water and upturned into a water - filled beaker is often used to capture gases, e.g. in electrolysis demonstrations . </P> <P> A test tube with a stopper is often used for temporary storage of chemical or biological samples . </P> <P> Culture tubes are test tubes used in biology and related sciences for handling and culturing all kinds of live organisms, such as molds, bacteria, seedlings, plant cuttings, etc...Some racks for culture tubes are designed to hold the tubes in a nearly horizontal position, so as to maximize the surface of the culture medium inside . </P>

Which of these is not correct about heating substances in a test tube