Effects of Chemical Reactions in Our Daily Life
Fermentation of fruits, digestion of food inside the stomach of the human body, respiration, burning of fuel, corrosion and rancidity are some examples of reaction in our daily life.
Corrosion
It is the process of oxidative deterioration of a metal surface by the action of substances present in the environment to form unwanted corrosion products. In other words, it is the process of formation of oxide or other salts on the surface of a metal when it is exposed to the atmosphere.
In this process, the metal surface which is in direct contact with air and moisture gets oxidized and forms a mixture of oxide and hydroxides. The process is continued until the metal is not destroyed completely.
e.g., conversion of iron into rust [Fe2O3.xH2O], tarnishing of silver (due to the formation of Ag2S), development of green coating of Cu(OH)2.CuCO3 (basic copper carbonate) on copper and bronze. It is basically an electrochemical process.
Corrosion of iron is called rusting. It is accelerated by the presence of impurities, H+ electrolytes such as NaCl, gases such as CO2, CO2, NO, NO2 etc.
It is prevented by the following methods
- By electroplating
- By surface coating (coating of surface with oil, grease, paint, and varnish)
- By alloying
- By galvanization of iron (process of deposition of a thin layer of zinc over iron surface)
- By anodizing (generally done by using aluminum metal as anode because it becomes passive due to the formation of its oxide layer over its surface)
- Food cans are coated with tin, not with Zn because Zn is more reactive than iron and hence readily converts into toxic substances.
- Formation of a layer of aluminium oxide over aluminium surface protects the metal from further corrosion.
- Platinum gold, silver are the metals that do not undergo corrosion and hence, are called noble metals.
Fermentation
Louis Pasteur discovered fermentation in 1857. In this process, complex organic compounds are decomposed by micro-organisms such as yeast bacteria into simpler organic compounds. It is an exothermic process, CO2 gas (H2 and CH4 in small amount) is evolved in this process and the apperance of gas seems like boiling the fermentative solution of the substance.
Examples of fermentation are
- Conversion of milk into curd through lactobacilli
- Preparation of wine and vinegar from sugarcane juice or preparation of ethyl alcohol from glucose by using yeast.
- In the baking industry for making bread, pastries, and cakes.
Rancidity
When oils and fats or foods containing oils and fats are exposed to air or oxygen, they get oxidized due to which the food becomes stale and its color and smell changes. This process is called rancidity.
It is prevented by the following methods
- Antioxidants like BHT (Butylated hydroxytoluene), N2 (dinitrogen) are added to foods containing fats and oils.
- The food is kept in airtight containers in the refrigerator or deep freezers