II.2.1.1. Crystallization
Crystallization is the method of separating a solid substance in the form of crystals from a homogeneous liquid mixture (solution), by evaporating the liquid substance.
🔥 Warning! This experiment is for teachers only!
Required Materials:
Berzelius Glass, Water, Bruise Stone Crystals, Wand, Asbestos Sieve, Alcohol cooking lamp, Match, Capsule, Tripod.
Experiment description:
- In the glass, mix the water with the bruised stone (copper sulfate) with the help of the wand.
- Put the formed mixture in a capsule that you place on the asbestos sieve on the tripod and heat it in the flame of the alcohol cooking lamp.
- What do you notice?
The water evaporates and bruised stone (copper sulfate) crystals are obtained in the capsule.
Experiment conclusion: Through crystallization, we separated a solid substance in the form of crystals from a homogeneous liquid mixture (solution), by evaporating water.
🔥 Caution! This experiment is performed only in the presence of an adult!
🔥 Warning! When working with fire sources make sure to keep your hair tight and don't wear clothes with wide sleeves! Be careful not to burn yourself when working with hot water!
🔥 Warning! The bruise stone (copper sulfate) is toxic. Don't touch it or taste it!
🔥 Caution! This experiment is performed only in the presence of an adult!
🔥 Warning! When working with fire sources make sure to keep your hair tight and don't wear clothes with wide sleeves! Be careful not to burn yourself when working with hot water!
🔥 Warning! The bruise stone (copper sulfate) is toxic. Don't touch it or taste it!
- Extraction of salt from seawater.
- Extraction of sugar from cane/sugar beet.
🔥 Warning! This experiment is for teachers only!
🔥 Warning! Sodium acetate is a compound with very low toxicity. It is slightly irritating to the eyes. Respiratory tract may be irritated after inhalation. Frequent and constant contact with the skin may cause irritation. Sodium acetate and sodium thiosulfate can be reused repeatedly. Just follow the basic principles of handling reagents in the chemistry lab.
Required Materials:
4 pahare Berzelius foarte curate (preferabil ca acestea să fie noi - să nu fie zgâriate), acetat de sodiu, tiosulfat de sodiu, spirtieră, stativ, sită de azbest, sticlă de ceas, termometru, dispozitiv Heat In a Click / Hot Pack sau comprese calde, apă.
Experiment description:
- Take a Berzelius glass, preferably new (so as not to be scratched) and very clean.
- Add sodium acetate trihydrate (CH3-COONa x 3H2O).
- Heat the sodium acetate and add a little water until you notice that a clear solution has formed (approx. 80-90°C). If a ring of crystals forms above the solution, on the inner edge of the beaker, pour the entire contents of the beaker into another clean beaker.
- Cover the beaker with a watch glass and let the solution cool. Note that the solution remains colorless and clear even when cooled to room temperature.
- Add a small crystal of sodium acetate to that solution and observe its behavior.
Sodium acetate crystallizes in mass, and this crystallization raises the temperature to 38-40°C.
Another reagent with a behavior similar to sodium acetate is sodium thiosulfate.
- Take a Berzelius glass, preferably new (so as not to be scratched) and very clean.
- Add sodium thiosulfate pentahydrate (Na2S2O3 x 5H2O).
- Heat until you notice that a clear solution has formed (approx. 80 - 90 °C). The salt dissolves in its own water of crystallization generating a clear, saturated solution at 90°C.
- Cover the beaker with a watch glass and let the solution cool. Note that the solution remains colorless and clear even when cooled to room temperature. It measures the temperature of the solution.
- Add a small crystal of sodium thiosulphate to that solution and observe its behavior. Measure the temperature again.
Allowed to cool, the solution becomes supersaturated and crystallizes in mass if a single sodium thiosulphate crystal is thrown into it to "seed the solution". Mass crystallization of sodium thiosulfate raises the temperature to 50 °C.
Experiment conclusion:
The increase in temperature justifies the use of this solution in the medical field, the respective devices being called Heat In a Click / Hot Pack or warm compresses. Supersaturated solutions of certain salts can be used in medical practice to generate heat to keep the wounded warm until they are safely in the hospital. The principle is simple: a supersaturated solution when it comes into contact with its own crystals generates mass crystallization of the entire solution, the process being exothermic, the released heat being used in medical practice.