Chapter: 4.0


The study of fluids has a long history. Archimedes, for example, was already engaged in the study of floating bodies in the time before Christ. Much later, Pascal focused on how the pressure changes in closed containers, while Bernoulli studied the flow of fluids.

Fluid mechanics is the study of fluids.

In this chapter you will learn:

  1. some properties of fluids,
  2. where you can observe the properties of fluids in your surroundings,
  3. how you can check the properties of a fluid by experiment.

Fluids are substances that have the common property: flow. They are divided into liquids and gases. We call this common property fluidity. A characteristic of liquids is that they form droplets. Fluids are stored in containers in which the liquids take the shape of containers. Gases are substances that fill the space they are in. Gases are usually compressed into a container.

Examples of fluids

Look around you, which fluids do you notice?

Examples of photos for liquids:

Examples of photos for gases:

  • butane, propane, carbon dioxide

Test yourself

Here are some examples of photographs of substances that you need to sort according to their aggregate states: liquids on the left and gases on the right.


-ink, water, oil, milk.


– butane, propane, carbon dioxide.