Cupric sulfate

Growing copper(II) sulfate crystals

Difficulty:
Danger:
Duration:
2 hours
Experiment's video preview
Chemical formula

Reagents

Safety

  • Put on protective gloves and eyewear.
  • Conduct the experiment on the plastic tray.
  • Observe safety precautions when working with boiling water.
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

Copper sulfate doesn’t dissolve completely. Would I still succeed with the experiment?

Don’t worry — it’s normal. In about 10 minutes after dissolving copper sulfate, pour the solution out into a Petri dish, so that the crystalline sediment remains in the plastic cup.

How to preserve the crystals?

With time, these crystals will “wear off” because the water they initially contained constantly evaporates. In order to slow down this process, coat the crystals with a colorless nail polish and seal them in a transparent container. Crystals are quite fragile, but with such a “protection” you’ll be able to enjoy its beauty for at least half a year (unless you decide to subject them to a structural test).

Step-by-step instructions

  1. Pour 100 mL of freshly boiled water in the beaker.
  2. Collect 10 mL of water with a syringe.
  3. Pour water taken with the syringe into a plastic cup. Add one vial оf copper sulfate CuSO4 (6.5 g).
  4. Place the cup into the beaker with hot water.
  5. Stir the contents in the cup for 10 min.
  6. Pour out the obtained solution into a Petri dish, so that crystalline sediment remains in the cup.
  7. Within an hour, crystals will start growing in the Petri dish. And in a couple of days, the crystals will become even larger!
Graphical step-by-step instruction

Expected result

A blue transparent crystal of cupric sulfate CuSO4*5H2O grows on a copper wire.

Disposal

Dispose of solid waste together with household garbage.

Scientific description

Why do crystals grow?

Copper sulfate belongs to those substances that dissolve in water better upon heating. And vice versa, their solubility decreases upon cooling, which in our case leads to precipitation of copper sulfate in form of beautiful blue crystalline hydrate CuSO4·5H2O. Due to the fact that the solution is cooled down slowly, the crystals grow gradually and become rather big.

Show more details

Why does the copper sulfate solution tend to form crystals but not a fine powder upon cooling? Crystals are very much different from amorphous solids (such as carbon black or glass): particles they consist of are arranged among themselves in a strict geometrical order inside a solid. Though, such clear complementarity is often unfavorable to nature. And still, such an arrangement of particles within a solid “feels” very comfortable to them. This means that each atom is strongly connected with its surroundings and that all positive charges closely interact with all negative charges.

Follow up

Big crystal

Small blue crystals of copper sulphate, without doubt, delight the eye. But what about growing a very big crystal? However, that is not so easy.

As a container, use a plastic cup (that way you can heat it just like the glass of tartaric acid or sugar in the other experiments of the kit) or a glass beaker. In the first case, you will need about 30 grams of copper sulfate CuSO4*5H2O. You can find it in a store where fertilizers are sold, or in a hardware store. If you decided to grow a very large crystal and to do it in a beaker, prepare in advance 60-70 grams of copper sulfate.

Fully dissolve the copper sulphate in hot water. Thoroughly mix the solution until there are no crystallites remaining. Use a piece of copper wire, thread or a splinter as the "support" of the crystal.

Now please be patient! A large crystal can grow for several days!

Crystallization in the refrigerator

How does the environmental temperature affect the rate and the result of crystallization? You can research that! Repeat the experiment, however prepare two test tubes with copper sulfate solution at the same time. In each of them you will need to add 5 grams CuSO4*5H2O, so use the solution and the crystals from the main experiment.

Stop after the 9th step in the instructions. Now, put one of the test tubes in a cup with hot water, as indicated in step 10, and put the second in the refrigerator (the temperature inside is about 4 Co).

Wait for 1-2 hours. Compare the results. Where did the crystal grow bigger? Where are there more of them and why?

Crystals of NaCl

Try to grow a crystal of the most common table salt - sodium chloride NaCl.

Dissolve 39 grams of salt in 100 ml of boiling water. Thoroughly mix the solution until there are no crystallites remaining. As the "support" for the crystal is best to use a thread wound on a splinter - lower its end into the solution. Tie a couple of knots on the end of the string - it may help.

Now all you have to do is wait! Make sure the glass is in a place where no one will shake or drop it over.

That's interesting!

Why grow crystals?

Many synthetic chemists discover and use different methods of single crystals growth in their work. So, why is it attractive and beneficial to professional chemists?

Besides an aesthetic effect (“I have synthesized a substance, and it forms beautiful crystals!”), there is a compelling need to asseamble molecules of new or unknown substances into perfectly ordered single crystals. Normally, after synthesizing a new compound, a chemist has to clarify (confirm) its molecular structure. Until he or she does that, no one in the world scientific community accepts his or her discovery.

There are numerous indirect methods to examine a substance molecular structure. For instance, chemists may expose a substance to visible or infrared light, strong magnetic field or another physical load, looking for hints about the order its atoms are arranged within molecules.

Among these methods, the most reliable and common approach to defining a new compound structure is a so-called X-ray crystallography analysis. It allows researchers to take a “snapshot” of a new substance lattice. This information, in turn, can immediately answer all questions about its molecular structure. Despite its effectiveness, though, this method has a very significant drawback: a substance must be analyzed in form of a single crystal.

It should be understood that each molecule, even if we are talking about very large molecules of polymers or proteins, is very, very small, which can only be detected with the help of special equipment and under strict conditions. Thus, unveiling the structure of a single molecule requires additional finesse. However, even a milligram of any substance contains a huge amount of identical molecules. If you assume that all the molecules respond equally to the same external exposure, and then sum up all these responses, then detection of that bulk signal becomes much easier.

As mentioned earlier, single crystals are unique in a way that their constituent “blocks” are in a strictly defined repetitive order. It allows for summing up the molecules responses to a certain effect, as they are all organized in space in the same way. X-ray analysis method assumes that substance molecules are responsive to X-ray irradiation. After these rays reach the substance molecules, they change their direction in a specific way, which depends on the arrangement of atoms in a single crystal.

Further, scientists analyze the pattern created by diffracted rays to define where atoms, which caused such a change, are located in the crystal. This knowledge makes it possible to figure out the substance molecular structure. Quite simply, if an atom is not a part of a molecule, then in most cases it will be detected being away from all other atoms in the molecule, at a distance of more than 3.5 angstroms, which is one hundred million times less than 3.5 centimeters.

By a curious coincidence, X-rays are also used to examine internal structures of a human body, as well as of many other living creatures. For example, in case of a bone fracture, X-ray radiograms (or just X-rays) of damaged body parts are taken, which lets a doctor know where exactly the fracture is located and how to treat it efficiently.