Chemical jellyfish

Drops of solutions turn into amazing jellyfish!

Difficulty:
Danger:
Duration:
10 minutes
Chemical jellyfish

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 drip the salt solutions from?

Try dripping the solutions at heights ranging from 1 to 15 cm so the “jellyfish” vary in size.

Can I keep the jellyfish?

Yes! If you want to save your jellyfish, leave the Petri dish to dry completely. In 2–3 weeks, you will have a multicolored disc of insoluble silicates.

The liquid glass isn’t spreading out to fill the Petri dish. What should I do?

If this happens, carefully take the Petri dish and swirl it in gentle circles on the table. This will help the liquid glass spread over the entire surface.

The FeSO4 looks iffy...

Yes, it may be not very attractive, but it works well. Feel free to continue the experiment!

Step-by-step instructions

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

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Now apply the solutions of metal compounds (called metal salts) to 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

If we take two substances  and  that can split up into parts called ions , and , , and mix them in a solution, these parts might form new substances— and . If even one of these new substances precipitates out ↓ or flies away as a gas ↑, we say that the substances entered into an ion exchange reaction.

In our experiment, sodium silicate Na2SiO3 enters into an ion exchange reaction with various salts, such as CuSO4. Separately, both of these substances exist in the form of the following ions in a solution: Na+ , SiO32- , Cu2+  and SO42- . But if we mix the solutions, the copper ions Cu2+  and silicate ions SiO32-  form insoluble copper silicates CuSiO3↓. Due to the viscosity of the liquid glass, these take the form of chemical jellyfish.

Why do the jellyfish appear in the liquid glass?

As you drip them into the Petri dish, the solution droplets don’t mix with the liquid glass as you might expect. Instead, they remain isolated, forming these fascinating structures we call silicate jellyfish. You have to agree, some of them look almost like the real thing!

Their intricate structure is largely due to the “splatter” effect as the drop impacts the dense solution from a certain height. Later on, we’ll discuss how adjusting the height of the fall might affect the structure of your jellyfish.

Learn more

So why don’t the drops dissolve in the liquid glass?

This is primarily due to the viscosity of the sodium silicate solution – the drop is kept quite compact to begin with. This is why you have to thoroughly mix the concentrated liquid glass with water; if you don’t, the jellyfish will fall apart in the less viscous areas.

So what is viscosity? One way of describing it is “lack of ability to flow” – the higher a substance’s viscosity, the less easily it flows. For instance, water is extremely easy to pour, melted chocolate less so, and honey even less so. Consequently, we would say that water is not very viscous at all, melted chocolate is more viscous than water, and honey is the most viscous of the three.

However, this is not the only reason why the drops retain their original form. You would still think that the drops would gradually dissolve in the liquid glass – so what’s stopping them? Honey dissolves in water! And we mixed the liquid glass with water easily! Something seems amiss.

As it turns out, rather specific chemical reactions between the drop and the liquid glass are forming insoluble structures. Below are just some of the reactions involved in the process. Keep in mind that liquid glass is, in essence, sodium silicate Na2SiO3.

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 rapidly form a thin film of insoluble compounds between the solution of liquid glass and the metal salt solutions. This film is what prevents the drops from dissipating!

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

As a matter of fact, this depends on how well you mix the water and liquid glass. The less carefully you mix the solution, the more likely the drop is to hit a watery or, conversely, a viscous area (where there is more liquid glass). The drops will dissipate less in a viscous environment, and more in a watery area.

However, let’s assume the solutions have been mixed thoroughly. If you drip the metal salt solutions from a height of about 1–2 cm, you’ll get little pellets resembling pieces of caviar. Perhaps the most beautiful jellyfish result from a dripping height of 5–10 cm. If you drip the solutions from about 20–30 cm (that’s a difficult task in itself; the plastic tray might come in handy), the drops will practically break apart upon impact. 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?

This experiment involves four solutions of metal salts: bluish copper sulfate CuSO4, yellow-orange iron chloride(III) FeCl3, colorless manganic sulfate MnSO4, and a yellowish-brown iron sulfate(II) FeSO4.

Each of the solutions is special in its own way. Let’s start with copper sulfate – a bluish solution of CuSO4, often called cupric sulfate. These jellyfish are the most stable of the bunch – they will retain their color and form for several days.

Jellyfish made of manganese(II) sulfate MnSO4 are transparent and look quite striking on a dark background – try placing some black construction paper or something similar under the Petri dish. Also, they gradually change their color, eventually turning pinkish-brown. Why? Each manganese Mn2+ ion (from MnSO4) can still donate at least 2 more electrons, which other atoms would love to poach! That’s exactly what happens: the oxygen in the air О2 gradually oxidizes the manganese to manganese oxide Mn_O{2}, which gives the jellyfish its color:

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

Why do we use two solutions containing iron ions? At first glance, the answer might seem obvious: each compound contains different anions (negatively-charged ions) – one contains chloride Cl-, and the other contains sulfate SO42-/. But this isn’t the main difference. Look closer – the iron is different! In the case of chloride, it's Fe3+; in the case of sulfate, it's Fe2+. The difference is in just one electron:

Fe3+ + e- → Fe2+ Fe2+ – e- → Fe3+

But the difference in properties, including color, is quite significant!

You may also notice small orange stains forming in the drops of the dark iron(II) sulfate FeSO4 jellyfish – this metal is oxidized by (i.e. loses one of its electrons to) the oxygen in the air. When this happens, their 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. The other ions involved in the experiment, Cu2+, Fe2+ and Mn2+, all have a lesser charge – twice the positive charge of an electron. Insoluble 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 difference in charge between the participants of the reaction, the stronger and faster they attract to each other.

This is why the iron(III) chloride reacts with the liquid glass a lot faster than the other salts – so quickly, in fact, that the forming insoluble compounds literally squeeze the drop out onto the surface of the liquid glass.

That's interesting!

What is liquid glass?

Liquid glass is a viscous, liquid solution of sodium silicate Na2SiO3, and rarely potassium silicate K2SiO3, in water.

How is it made? One might think that it would be easiest to dissolve silicates in water, but this method is ultimately very expensive. Instead, a concentrated solution of alkali (NaOH) and a mixture of raw materials containing silicon dioxide (SiO2) are heated at high pressures on an industrial scale.

Structurally, however, this substance isn’t quite sodium silicate Na2SiO3. It would be more 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?

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

Additionally, flammable materials such as fabric, wood, and cardboard are treated with liquid glass to keep them from catching fire. Liquid glass is often used to reliably glue paper and cardboard.

How does liquid glass react with normal glass?

You should observe caution when handling liquid glass with normal glass. If sodium silicate dries on normal glass, it will render the normal glass opaque.

Why does this happen? It’s quite simple, really – normal and liquid glass are based on very similar silicate compounds. In essence, the normal glass dissolves slightly in the liquid glass, marginally altering its surface structure and making it opaque.