Test tubes are a common piece of laboratory equipment consisting of a finger-like length of clear plastic or glass tubing, open at the top, usually with a rounded U-shaped bottom. They are widely used in science for various purposes, including:
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Handling chemicals: Test tubes are widely used by chemists to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays.
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Culturing organisms: In biology, test tubes are used to culture or grow samples of various organic materials such as bacteria, mold, and yeast.
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Heating liquids or solids: 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 vapors to condense on its walls.
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Capturing gases: A test tube filled with water and upturned into a water-filled beaker is often used to capture gases, for example, in electrolysis demonstrations.
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Storing samples: Test tubes are used in medicine and forensics to store samples of blood or other fluids.
Test tubes are not used for measuring precise volumes of liquids, but they are used primarily for qualitative observations of biological, biochemical, or chemical reactions.
