Laboratory equipment

Many guides just state the names of these without explaining why they exist, but I will include examples. This helps to understand things such as why we have differently-shaped containers of the same volume:

Volumetric flask:

This the most accurate flask for measuring volume. This is because the main source of inaccuracy in volume is judging whether the miniscus is touching the volume-marking:

The error range of this increases as the width of the container increases. That's why a container with a thin neck is useful for accuracy. A volumetric can also be sealed with a stopper.

Beaker:

These are not so good at measuring volume, but are much safer to use when pouring out chemicals from a large storage container:

Typically you will want to pour them into a beaker first, then into a measuring cylinder or flask. Using the beaker as an intermediate will greatly reduce risk of spillage.

Erlenmeyer/conical flask:

This flask can used for titrations, where the neck is big enough to fit the end of a burrette into, yet the shape prevents splashing. Likewise for using a magnetic stirrer, or if you want to gently swirl the container without spillage.

Watch glass:

A watch glass is a circular piece of glass, convex on one side and concave on the other. It can roughly cover an erlenmeyer flask or a beaker, which helps prevent contamination or escape of vapour.

As a clean, dry, and unreactive surface, it can also be used for drying or weighing a solid powder: