Which type of glassware is not appropriate for heating liquids in an open flame setting?

Pipettes are not appropriate for heating liquids in an open flame setting primarily because they are designed for the precise measurement and transfer of small volumes of liquids, not for the containment or heating of those liquids. Most pipettes are made of materials that can easily deform or break under heat exposure, especially when heated directly by an open flame.

In contrast, flasks, beakers, and test tubes are specifically meant for heating. They are typically made from borosilicate glass, which can withstand thermal stress. Their design also accommodates heating on a hot plate or in an oven, making them suitable for various laboratory applications where heat is necessary. Flasks often have a wider bottom and a narrow neck, allowing for efficient heating and mixing, while beakers provide a large, open surface area for heating liquids. Test tubes, while also small, are designed to hold liquid and can be safely heated using a Bunsen burner as long as they are not subjected to sudden temperature changes.

Understanding the specific uses and properties of each type of glassware helps to ensure safety in the laboratory, guiding proper practices when handling chemicals and heat sources.