Learning outcome:

1. Edible salt, its preparation and uses.
2. Baking soda/ powder, its preparation and uses.
3. Vinegar, its preparation and role to preserve foods.
4. A brief discussion on soft drinks.

Household Chemistry

we use different kinds of chemical substances such as table salt, baking powder, vinegar, and soft drinks in our houses.

Table Salt or Edible salt

Sodium chloride (NaCl) is known as table salt or edible salt.

Preparation of Table Salt

NaCl along with a little quantity of some other salts including MgCl₂ are dissolved in sea water at a larger scale. Again sufficient sodium chloride (NaCl) is found in the underground as minerals. Various country like Bangladesh, table salt is extracted from sea water.

Firstly, salt cultivators in the coastal areas of Bangladesh make dams around the square or rectangular land of different sizes and keep a small empty space in every of them to enter the tide water. Then closing the entry point tide-water is reserved inside. When this water gets emaciated in sunlight salts become visible there. This method is called salt harvesting. This type of salt obtained contains sand. So, it is further treated through the different process in factories to convert it into edible salt.

Secondly, when the salt is mixed with water in a pot, it is dissolved in water but the sand remains at the bottom of the pot. Then the salt-water solution is separated through filtration.

Salt harvesting in the coastal area

Thirdly, when this sand free salt-water solution is heated, the water vaporizes but the salt remains at the bottom of the pot. In this way, the processed salt is packed and sent to the different places for sales.

Uses of NaCl

(i) Our body needs different types of ions like Na⁺, K⁺ etc. for all normal activities in our body. If there is any lacking of Na⁺ in our body due to any reason, this deficiency is filled up by taking NaCl with water.

(ii) We eat rice with curry. The curry does not taste good if we do not use NaCl salt in it.

(iii) NaCl is used in industries to prepare NaOH compound.

(iv) NaCl is widely used in drug industries to manufacture salines for diarrhoea or dehydration.

Baking Powder

The chemical name of baking soda or table soda is sodium hydrogen carbonate (i.e. NaHCO₃₎.

Preparation of Baking Soda

Firstly, a saturated solution of NaCl is prepared by dissolving NaCl in water. Secondly, this saturated solution is further saturated by blowing NH₃ gas into it. Finally, CO₂ gas is blown into NaCl solution saturated by NH₃. In this stage, at first CO₂, NH₃ and H₂O together produce Ammonium Hydrogen Carbonate (NH₄HCO₃).

Then, this NH₄HCO₃ reacts with sodium chloride and produces sodium hydrogen carbonate or baking soda (NaHCO₃). Baking soda is separated from the reaction pot. When the tartaric acid (C₄H₆O₆) is mixed with baking soda (NaHCO₃). This mixture is called baking powder.

Baking Powder

Uses of Baking Soda

Baking powder is usually used in making cakes. During making cakes, it is mixed with the flour of cake and heated. Now, do you know why does the cake rise/ swell up?

This is because, baking soda reacts with tartaric acid (C₄H₆O₆) in the mixture to produce sodium tartrate (C₄H₄Na₂O₆), CO₂ gas and H₂O. Here, cakes rise up because of this CO₂ gas.

Sometimes we use one type of fungus named ‘Yeast’ in our home or bakeries to inflate bread. To do this, yeast is added to a solution of sugar initially. If the dough is made with this yeast- sugar mixture solution and kept in a warm place then CO₂ is produced due to aerobic respiration of the yeast. Hence, this CO₂ helps the cakes to swell up. When the bread is baked in the oven after sufficient blow-up then the yeast dies in heat and the blow-up process of bread stops.

Vinegar

Vinegar is a liquid substance. 4% to 10% liquid solution of ethanoic acid (acetic acid) is called Vinegar.

White vinegar

Preparation of Vinegar

It is prepared by blowing the bubble of oxygen gas into ethanol and acetobacter is kept in a steel pot at (25-35) °C temperature.

Roles of Vinegar in Preserving Food

Pickles get putrefied or rotten if bacteria attack them. But if vinegar is applied to them, bacteria cannot attack them. We know the main element of vinegar is ethanoic acid. The protein released by ethanoic acid damages H⁺ bacteria. As a result, the foods remain safe from the attack of bacteria. In this way, food is preserved by using Vinegar.

Soft Drinks

A soft drink typically contains carbonated water, a sweetener, and a natural or artificial flavouring. The sweetener may be sugar, fruit juice, high-fructose corn syrup, sugar substitutes or some combination of these.    

Soft drinks

Soft drinks are prepared when carbon dioxide gas is dissolved in water at the cold state and high temperature. CO₂ and H₂O react in the soft drink to produce H₂CO₃. Some examples are coca-cola, sprite etc. People take soft drinks for the digestion of food.

 

*References: NCTB, Google and Wikipedia.