How to make a liquid engine

A liquid motor is a simple, but quite didactic experiment, where we can visualise the effects of electrochemical reactions and magnetism simultaneously, causing a movement that can be used to make mixtures. Today, we will see how to make a liquid engine with few materials and that can serve as a good science project.

Liquid engine


- A metal cup.

- Cables for electrical connections.

- Copper (II) sulphate solution or a salt water solution.

- One 9V battery.

- A copper tube or a graphite rod.

- Plastic or rubber insulating sheeting.

- A large and powerful magnet.

- A pair of crocodile connectors.

Creating the liquid engine

The first step is to place an insulating foil at the bottom of the beaker so that only the walls of the beaker become the electrode. Then, we are going to place the glass on top of the magnet by placing an insulating foil between them.

Once the glass is in place, it is time to connect the negative pole of the battery to the metal glass and the positive pole to the copper pipe or the graphite sheet with cables and crocodile connectors. Then, we place the pipe or the graphite rod inside the glass.

Now our experiment is almost ready, we only need to add the saline or Copper (II) Sulphate solution inside the beaker until it covers a large part of the electrode, and after a few minutes, we will be able to see how the liquid inside the beaker starts to move around the electrode, as if it were a kind of blender or mixer. Also, we will be able to see an orange powder (in case we use copper pipe) on the walls of the glass.

View of the magnetic fields

How it works

When we close the electrical circuit, there is a movement of electrons inside the vessel which is known as an electrochemical redox reaction. This movement of electrons between the electrodes (vessel and pipe) generates an electromagnetic effect by generating a magnetic field perpendicular to the movement of the electric current. This field collides with the magnetic field generated by the magnet, thus, we can observe a movement of the liquid inside the vessel, a principle quite similar to the one in the electric motors. The orange powder is reduced Cu particles that adhere to the vessel walls due to the electrochemical effect.

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