Neutralization is not the only experiment with acids and alkalis. Let's peel the oranges.
Speaking of acid-alkali, students who are not good at science will run away just by listening. Since the acid-alkali reacts with the mandarin orange peel, I adopted this experiment so that I could think that it was a chemical change that was familiar to me.
Experiment 1: Peeling oranges with hydrochloric acid and sodium hydroxide
you need : 0.4 mol hydrochloric acid 250 ml, 0.3 mol sodium hydroxide 250 ml, mandarin oranges, beaker, heating equipment, colander
Peel the mandarin oranges and separate them into bunches. Bring hydrochloric acid to 50 ° C and simmer for 10 minutes. The endothelium of mandarin oranges is made of pectin. Hydrochloric acid hydrolyzes the ester groups of pectin. Do not use a metal pot as it uses acid.
After washing with water, heat with sodium hydroxide at 50 ° C for about 10 minutes. The hydrolyzed pectin is converted to a sodium salt and dissolved in water. Wash with water. The skin can be removed cleanly.
In the old days, it was peeled in this way, but now it is mechanically peeled. Since hydrochloric acid and sodium hydroxide are used, the tentacles of the students do not grow well.
Experiment 2: Peeling oranges using citric acid and baking soda
The same experiment is performed at 60 ° C with 2% citric acid for 10 minutes and at 60 ° C with 2% baking soda for 10 minutes. Both are food additives, so it's a little safe. However, it is better not to use a pot (because the acid reacts with the metal).
Experiment 3: Recommended! Peeling oranges using only baking soda
you need : 2 teaspoons of baking soda, 5 or 6 tangerines, pan, heating utensil, colander
Add 2 teaspoons of baking soda to 1 liter of boiling water. Add tangerines and simmer for 1 minute and 30 seconds. Cool the tangerines. Gently add water (so as not to break the oranges). Change the water several times to wash off the baking soda. Take the thin skin by hand.
This method is quoted from a cooking channel called “Roku Kitchen”. Students can eat with peace of mind, and since only baking soda is available, they can experiment in a pot.