A test tube is a long cylindrical handheld tube shaped like a finger that is used in various experiments. It is a common piece of laboratory equipment that is used to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays. The following are some of the functions of test tubes:

• Holding, mixing, or heating substances: The primary function of a test tube is to hold, heat, or mix substances used in experimentation. Test tubes are convenient containers for heating small amounts of liquids or solids with a Bunsen burner or alcohol burner. 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.

• Analysis of chemicals: In the chemistry laboratory, a test tube is useful to study chemicals. The physical and chemical properties of chemicals can be tested and experiments can be performed in different forms between two or more chemicals.

• Preparing culture media and collecting samples: In microbiology laboratories, test tubes are used to prepare culture media, collect samples, and hold fluids.

• Disease diagnosis: Test tubes are used in clinical and microbiological laboratories to collect samples and blood and to perform various tests, especially in culturing cancer cells and biochemistry tests.

• Storing samples/chemicals: Test tubes are also used to store and keep chemicals and samples for future tests.

Test tubes come in different types depending on the material and purpose of the experiment. Some of the common types of test tubes include:

• Graduated test tube: This type of test tube is like a graduated cylinder and is used to precisely measure samples before performing experiments. Usually, the tube has a thick wall and an interchangeable glass stopper.

In summary, the function of a test tube is to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays. It is also used to prepare culture media, collect samples, and hold fluids in microbiology laboratories, and to collect samples and blood and perform various tests in clinical and microbiological laboratories.