Thermal expansion of liquids

Now you can see how the liquids rise in the tubes. The oil rises the fastest and overflows quite quickly. Then the milk follows and finally the tube with the water. All three liquids overflow.

Fill each of the three Erlenmeyer flasks to the top with one of the three liquids (sunflower oil, milk, water). Now insert the glass tubes into the perforated rubber stoppers and place them on the three Erlenmeyer flasks. Make sure that the level in all the glass tubes is the same. Then place the three containers in the bowl. Bring the water to the boil and pour it into the bowl so that it surrounds the flasks.

• three equal-sized Erlenmeyer flasks,
• bowl,
• water,
• three perforated rubber stoppers,
• three matching glass tubes with the same inner diameter,
• electric kettle,
• sunflower oil,
• milk,
• water,

When the rubber stoppers are placed on the Erlmeyer flasks, the liquid level in the tubes should not rise too high; an evenly low level of all three liquids would be good. This is the only way to accurately observe the different rises. The glass tubes should be inserted into the rubber stoppers in such a way that the tubes do not protrude at the bottom. Moisten the stoppers when inserting the tubes.

What is technically behind the experiment

Solid bodies, liquids and gases generally increase in volume when they are heated. Model concept: Substances are made up of molecules that are not at rest, but perform rotational movements as well as back and forth movements. If thermal energy is added to a substance, the speed of the movements increases and the molecules are generally further apart. They therefore require more space and the substance expands. This expansion can be observed by the rise of the liquids in the glass tube.

What the experiment has to do with everyday life

Thermometers contain a substance that expands when it is heated. This substance then rises in the tube and indicates the temperature. A deviation from the rule is water between 0 and 4o. In this temperature range, the volume does not expand when heated, but shrinks. (Anomaly of the water.)

Sandra Raabe