type of laboratory glassware; container with a narrow neck

A flask is a type of container made of glass. They are a common piece of apparatus used in laboratories. Their size are chosen by the volume they can hold, and is measured in metric units, like litres (L) or millilitres (mL). Their shape depends on what they are used for, but they usually consist of a wider body, which contains the materials, and a more narrow neck with an opening at the top. The opening is the way to insert materials into the body. Some flasks have more than one neck and opening at the top.

An Erlenmeyer flask or conical flask

Flasks are used to contain substances. They are usually made of glass or borosilicate glass (Pyrex). This is to ensure that the substances inside the flask do not react with the flask itself, due to the volatile nature of many chemicals (such as hydrochloric acid), They can be used to heat a substance. There are many different types of laboratory flasks. They differ in their shape and what they are used for. The most common types of flask are:

Flasks can be used to make and hold solutions, to measure chemicals, and to contain chemical reactions like boiling, precipitation and analysis.