Essay Lab on Chemistry: How is hot ice made?

This experiment aims at creating hot ice and then crystallizing it from its solid-state and make an original science essay on it. A supersaturated solution of sodium acetate is known as hot ice and it has the unique ability to form crystals in its pure form. During the crystallization process of hot ice, sodium acetate trihydrate usually forms through an exothermic reaction (Fleming, 2019).

The purity of hot ice increases through recrystallization where after obtaining crystals from the crystallization process and reheating them with little water. This experiment also shows reversible and irreversible reactions that occur to sodium acetate.

Results

Formation of hot ice

Crystallization

Production of heat in an exothermic reaction

Experiment narrative

500ml of vinegar was measured and put in a clean beaker. 60 grams of baking powder was then added to the beaker in small amounts after every 30 seconds. The contents in the beaker were then oiled for 15 minutes continuously. After heating the contents, the solution was then covered tightly so that no more water can be lost through evaporation. Additionally, it was allowed to cool and this was reinforced by putting it in a refrigerator for 10 minutes. The solution was then removed from the refrigerator and a crystal of sodium acetate trihydrate carefully dropped in it to crystallize. Again, 160g of sodium acetate trihydrate was put in a beaker containing 40ml of water. The contents were mixed by stirring and then heated for 15 minutes. The solution was put in the refrigerator to cool for 10 minutes before a crystal of sodium acetate hydrate was put inside it to crystalize. After completing both steps, the formed crystals were dried using a clean paper towel and then measured.

Calculations and error

Theoretical yield (T.Y) of sodium acetate trihydrate = moles of sodium acetate trihydrate formed in step 1

In this equation, Baking soda + vinegar à sodium acetate + water + carbon dioxide

NaHCO_3(s) + CH₃COOH_(l) à CH₃COONa_(aq)+ CO_{2 (g)}+ H₂O_(l)

Mole ratio of the reaction is 1:1:1:1

Moles of NaHCO₃ used = 60/84 = 0.7143 moles

If the moles of sodium bicarbonate is 0.7143 moles, then sodium acetate trihydrate formed is 0.7143 moles

Moles of sodium acetate trihydrate formed is 0.7143 moles

Mass = 82 x 0.7143 = 58.57g (theoretical yield)

Actual yield (A.Y) from the second experiment produced 25.3g

% error = (T.Y – A.Y)/ A.Y x 100

                                = (58.57 – 59)/58.57 x 100

                               = 0.7342 %

Sources of error from the experiment included:

1. More water loss due to increased evaporation
2. Loss of crystals during the drying process before measuring their weight
3. Impurities were present in one of the reactants.

Discussion and conclusion

From the experiment, sodium acetate trihydrate formed crystals according to the expectations. Again, a comparison was done between the different yields of sodium acetate trihydrate to see measure the percentage of error in the experiment. The errors that were present in the experiment dramatically influenced the final result. Any type of error leads to inaccurate results in any experiment (“Types of Experimental Errors”, 2019).

In this experiment, an irreversible reaction occurs between vinegar and baking soda to form sodium acetate trihydrate. New products are usually formed from irreversible reactions (“Reversible vs. Irreversible Reactions”, 2019). This is a neutralization reaction since was between an acid and a base that produced salt, water, and gas. Additionally, since the reaction required heat, it was endothermic since the heat was used to favor forward reaction as well as building new chemical bonds. While in solution form, sodium ion displaced acetate from its compound to produce sodium acetate trihydrate. Water and carbon dioxide was produced in the process. Considering that fizzing occurs when adding baking powder to acetic acid. The ionic equation of the neutralization reaction is shown below.

CH3COOH + Na⁺[HCO3]^– → CH3COO^– Na⁺ + CO₂ + H₂O

The Scientific explanation of what happens:

Under normal circumstances, when the solute is put in water and stirred, the solute dissolves in the solvent to form a homogenous solution if it is soluble in water. The solvent takes in the solute until a point where it becomes saturated and no more solute can dissolve in it. Heat is usually used to make the solutes dissolve faster. Adding sodium acetate trihydrate to the already boiling water makes the solution supersaturated (“Supersaturation – UW Dept. of Chemistry”, 2019). Cooling this solution makes crystallization occur spontaneously at any point.

Observations

When adding baking soda to vinegar, fizzing occurred during the reaction. Considering that the reaction was rigorous, sodium bicarbonate was added in small portions at 30seconds intervals.

This ensured that the reactants reacted completely and there was no loss of the products. The fizzing of the reaction is shown in Figure 1 below

 Figure 1

As the solution of sodium acetate trihydrate was heated, the heat increased the kinetic movement of the molecules such that the crystals dissolved faster. The heat was continuously applied until all the crystals had dissolved entirely. Moreover, evaporation also contributed to reaching the supersaturation point of the solution. The homogenous solution was then refrigerator to allow it to supercool. The oiling appearance of the sodium acetate trihydrate crystals is shown in Figure 2 below

Figure 2

When the supercooled solution of sodium acetate trihydrate was transferred to another clean beaker and a crystal of hot ice added to it, a fountain-like large crystal was formed and the heat was produced during the crystallization process. The solute created a nucleation site which made the bond between the solutes greater compared to the bond between the solute and the solvent. The formation of the large crystal is shown in Figure 3 below.

Figure 3

In this case, after reacting to the two reactants to form sodium acetate trihydrate in water, the solution water heated to a point where it became supersaturated. The supersaturated solution was supercooled and the refrigerator was also used to cool it further. This was to ensure that the contents in the beaker remain cold and ready for the next step which was crystallization. After cooling for about 15 minutes, the homogenous solution was now cold. Putting a crystal of sodium acetate trihydrate lead to the formation of crystals at a point in which the solute was added in the solution. Sodium acetate in solution form is very unstable and this increase if it is cooled. Adding the solute crystal in the solution created a nucleation site and this causes the force holding molecules to increase more than the force between solute and solvent molecule (“Nucleation of Crystals from Solution: Classical and Two-Step Models”, 2019). Additionally, considering that heat is usually given out during the crystallization, the reaction is often exothermic and this can be felt through the increase in temperature of the contents in the beaker.

Reference

Walker, C. (October 25). S1 Episode 0: Who Killed Alberta Williams? [Web log post]. Retrieved December 9, 2018, from https://podcast-a.akamaihd.net/mp3/podcasts/missing-GCDZNxIv-20180302.mp3

Fleming, D. (2019). Hot ice. Retrieved 20 September 2019, from https://eic.rsc.org/exhibition-chemistry/hot-ice/2000049.article

Nucleation of Crystals from Solution: Classical and Two-Step Models”. (2019). Retrieved 20 September 2019, from https://pubs.acs.org/doi/10.1021/ar800217x

Reversible vs. Irreversible Reactions”. (2019). Retrieved 20 September 2019, from https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Dynamic_Equilibria/Reversible_vs._Irreversible_Reactions

Supersaturation – UW Dept. of Chemistry”. (2019). Retrieved 20 September 2019, from https://depts.washington.edu/chem/facilserv/lecturedemo/Supersaturation-UWDept.ofChemistry.html

“Types of Experimental Errors”. (2019). Retrieved 20 September 2019, from http://www.physics.nmsu.edu/research/lab110g/html/ERRORS.html