Which laboratory device is most commonly used for heating small samples?

The most commonly used laboratory device for heating small samples is a test tube. Test tubes are specifically designed for holding small amounts of liquids or solids and can withstand heating when placed on a hot plate or over an open flame. They have a narrow shape, which allows for more efficient heating and easy observation of the contents.

In contrast, beakers are typically used for mixing and holding larger volumes of liquids, but their wider opening makes them less efficient for heating small samples. Graduated cylinders are primarily designed for measuring liquids accurately and are not used for heating. Pipettes are instruments used for transferring small volumes of liquids and are not suitable for heating at all. Thus, when it comes to safely and effectively heating small samples in a laboratory setting, the test tube is the ideal choice.