Volumetric flask
A volumetric flask is a pear-shaped flask with a long thin neck and a single line marked on it.
What is it for?
It measures one exact amount of liquid, like exactly 100 millilitres, so scientists can make mixtures of just the right strength.
How to use it
Fill it until the bottom of the curved liquid surface sits exactly on the line, with your eyes level with the mark.
🥽 Safety tip: These flasks are for measuring, not heating, because heat makes the glass expand and the measurement goes wrong.
Fun fact from Fizzy: The curved surface of a liquid in a thin tube has a special name: the meniscus.
How it makes a perfect mixture
Say a scientist wants a salt solution of an exact strength. They weigh out the salt, tip it into the flask, add some water and swirl until it dissolves. Then they add more water, slowly, until the liquid reaches the line, and turn the stoppered flask over a few times to mix it.
Because the line is on such a thin neck, even one extra drop shows up clearly. That is what makes this flask so accurate.
Where you would see one
Volumetric flasks are used wherever exact strengths matter: testing drinking water, checking food, and making medicines. Each one is made for one size only, such as 50, 100 or 250 millilitres, and the size is printed on the glass.