Chemical jellyfish

Drops of solutions turn into amazing jellyfish!

Difficulty:
Danger:
Duration:
10 minutes
Experiment's video preview

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the tray.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.

FAQ and troubleshooting

What is the optimum height to release drops of salt solutions?

Try dropping the solutions at different heights from 1 to 30 cm, so that “jellyfish” would vary in sizes from small to large.

Step-by-step instructions

Pour the sodium silicate (liquid glass) solution into the Petri dish.

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Now apply the metal salt solutions onto the surface of the sodium silicate solution.

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An ion exchange reaction occurs between the sodium silicate and the metal salts. As a result, insoluble metal silicates form. These resemble jellyfish!

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The water will gradually evaporate and leave behind a multicolored layer of insoluble silicates.

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Disposal

Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with an excess of water.

Scientific description

Why do the jellyfish appear in the liquid glass?

When you drip the solutions onto the liquid glass the drops don’t mix with it. This is the reason that the fascinating structures appear. These are called silicate jellyfish. You have to agree, some of them look like the real thing!

So how does this happen? The drop falls because of gravity; on its way it meets a hurdle – the surface of the liquid glass. A similar thing can be observed if you drop a capsule with paint onto a hard surface from a height of a couple of meters – the capsule will break and the paint will splatter all around the point of contact. In our case, the hurdle is a thick liquid-liquid glass. For this reason, the drop of liquid solution doesn’t splatter as much. You can read on the height dependence further on in the text.

Learn more

So why don’t the drops dissolve in the liquid glass? First of all, this happens because of the sodium silicate solution viscosity – the drop is originally quite compact. This is why you have to thoroughly mix the concentrated liquid glass with water, otherwise, the jellyfish will fall apart in the less viscous areas.

So what is viscosity? A way of describing it is that it’s the ability to flow – water can be easily poured from a bottle but melted chocolate will do this a lot slower, honey – even slower. This means that water has a lower viscosity than that of melted chocolate and the largest viscosity out of the three materials is that of honey.

However, this is not the only reason why the drops retain their original form. You would think that a drop would gradually dissolve in liquid glass – so what’s stopping it? Honey dissolves in water! And the liquid glass we were also able to easily mix with water! Something is amiss.

The solution is on the surface pun intended - in our case there are rather specific chemical reactions that happen between the drop and the liquid glass. In essence liquid glass is sodium silicate Na2SiO3. Non-soluble structures appear. Here are just some of the reactions: 3FeCl3 + 3Na2SiO3 → Fe2(SiO3)3↓ + 6NaCl CuSO4 + Na2SiO3 → CuSiO3↓ + Na2SO4

CuSO4 + Na2SiO3 + H2O → Cu(OH)2↓ + Na2SO4 + SiO2

These reactions occur quite fast, in fact, they form a thin film of non-soluble molecular entities between the solution of liquid glass and solution of metal salt. So the drops can’t dissipate!

How does the height of the fall of the drop affect the form of the jellyfish?

As a matter of fact, this depends on how well you mixed the water and liquid. The worse this is done – the more likely you are to hit a waterier area (more water) or more viscous are (where there is more liquid glass). In a viscous environment, the drops will dissipate less, at the same time in a waterier one they will dissipate more.

However, we will mix the solutions thoroughly.

When you drip the watery solutions from a height of about 1-2cm then you’ll get little pellets which look kind of like pieces of caviar. We would say that the most beautiful jellyfish are formed from a height of 5-10cm. If you drip the solution from about 20-30cm (that’s a hard task in itself, the plastic tray can come in handy) then the drops almost break apart upon contact. This resembles the previous example with paint. The higher you go, the more the drop will splatter across the petri dish. That is, of course, if you hit the mark!

What’s the difference between the four solutions?

In this experiment, we use four solutions of metal salts. This is a blueish copper sulfate CuSO4, yellowy-orange iron chloride (III) FeCl3, colorless manganic sulfate MnSO4 and a yellowy-brown iron sulfate (II) FeSO4. At large: they react with liquid glass, forming non-soluble compounds, this is why jellyfish form. First of all, they differ in color – the more variety in color – the merrier!

You can read further on the differences here

Each of the solutions is special in its own way. Let’s start with copper sulfate – a blueish solution of CuSO4, which many playfully call cupric sulfate. These jellyfish are the most stable – the color and form are retained even after a couple of days.

Jellyfish made out of manganic sulfate MnSO4 are transparent and look quite nice with a dark background – try placing a black piece of paper or something of the like under the petri dish. Also, they gradually change their color – they become pink-brown. Why does this happen? Manganese has the form of Mn2+ – this means that it has a lot of electrons which other atoms would love to poach! That’s exactly what happens, oxygen in the air О2 gradually oxidizes the manganese to manganese oxide Mn_O{2}, which gives the jellyfish it’s color:

Mn2+ – 2e- → Mn4+ MnSO4 + O2 → MnO2↓ + SO42-

Why do we have two solutions which contain metal? Of course, there are various anions (negatively charged ions) near the iron – chloride Cl- and sulfate SO42- respectively. But this isn’t the main difference. Look closer – the iron is different! In the case of chloride it's Fe3+ and in the case of sulfate, it's Fe2+. The difference is only in one electron: Fe3+ + e- → Fe2+ Fe2+ – e- → Fe3+ But the difference in properties which include color is quite significant!

You may also notice small orange stains, these form in the drops of the dark jellyfish made of iron(II) sulfate FeSO4 – this metal oxidizes (it loses one of its electrons) by the oxygen in the air. After that, the color starts to resemble that of the iron(III) chloride jellyfish!

Another interesting property of iron(III) chloride FeCl3 is the speed at which it reacts with sodium silicate. Why is this? The 3+ next to the iron ion Fe3+ means that the iron ion has triple the positive charge of an electron. Other ions which can be found in the experiment are – Cu2+, Fe2+ and Mn2+ all have a lesser charge – twice the positive charge of an electron. Non-soluble silicates form when a positively charged particle of iron (let’s say Fe3+) meets a negatively charged particle of the silicate SiO32-. The greater the charge of the participants of the reaction – the stronger and faster they attract to each other.

This is why the iron chloride (III) reacts with the liquid glass a lot faster than do the others. Jellyfish appear so quick that the formed non-soluble compounds literally squeeze the drop out onto the liquid glass surface. This is an interesting phenomenon which can be observed closely in a video of the experiment.

That's interesting!

What is liquid glass?

Liquid glass is a thick liquid – this is a solution of sodium silicate Na2SiO3 and rarely potassium silicate K2SiO3 in water.

How is it acquired? You would think that the easiest way would be to dissolve silicates in water. But it turns out that this is a very expensive method. On an industrial scale a mix of raw materials and a concentrated solution of alkali (NaOH) are heated at high pressures. The raw materials contain silicon dioxide (SiO2). This is how sodium silicate is made.

In reality though, this isn’t quite the same substance as sodium silicate Na2SiO3. It would be correct to write Na2O(SiO2)n because the solution still contains quite a lot of silicon dioxide and related substances. Normally n = 1,4 – 1,8.

What is liquid glass used for?

Liquid glass is used in construction as a binding solution in the preparation of concrete and cement.

Also flammable materials such as fabric, wood and cardboard are treated with liquid glass to prevent them catching fire. Often liquid glass is used for reliable gluing of paper and cardboard.

How does liquid glass react with normal glass?

You should be careful when handling liquid glass with normal glass. If some sodium silicate dries on normal glass it will render it opaque.

Why does this happen? It’s quite simple really – both normal and liquid glass have very similar compounds as their base – silicates. In essence liquid glass slightly dissolves in normal glass (to be completely fair it’s the other way round – normal glass dissolves in the liquid form). The structure of the surface of normal glass is slightly altered and it stops being transparent.