Changes that occur only in one direction or changes that are permanent are known as irreversible chemical changes.
Irreversible chemical change examples include much day- to- day work like cooking, eating, digesting, etc. Burning of fire-crackers, combustion, rusting, leaves changing color, decomposition of food are also some irreversible chemical change examples that we observe frequently.
When an irreversible chemical change occurs, internal properties of material change. Properties like boiling point, melting point, molecular mass, color, odor, etc., change.
In this section, we’ll study in detail about some of the irreversible chemical change examples.
List of Contents
Combustion of Fuel
Combustion of fuel is an irreversible chemical change example. In this type of reaction, the fuel combines with oxygen in the air and emits products such as carbon dioxide and water vapor.
The direction of the arrow is only in one way, which coveys that the reaction is irreversible.
Combustion of fuel is as simple an example as burning of wood or baking a cake. Once the wood turns to ashes, the ashes cannot be turned into wood again; likewise, once the cake is baked; we cannot un-bake the cake. Cake cannot be transformed back into flour, egg, sugar, etc.
Similarly, in the above chemical process, the reaction between carbon dioxide and water cannot create fuel and oxygen.
Read more about Chemical Change Examples
The Process of Ripening of Fruits and Vegetables
The ripening process of any fruit or vegetable is considered as an irreversible chemical change example as once the fruit is ripened, it cannot be reversed as a raw fruit. Though the ripening of fruits and vegetables is not an entirely chemical process, it is a bio-chemical change.
As a bio-chemical change, numerous enzymes, genes, and acids work together, breaking and making chemical bonds to alter the fruit and vegetable from being raw to ripe. Chiefly, ethylene gas is responsible for ripening of fruits and vegetables and is often referred to as the ‘Food Ripening Hormone.’
In the above image, the extreme left green – colored banana is the raw banana and the extreme right yellow banana with brown spots indicates ripened banana.
Every so often, we hear that raw fruits and vegetables have different advantages as well as disadvantages from ripened fruits and vegetables. Sometimes, unripe fruits and vegetables have better health benefits than ripe fruits and vegetables.
The Process of Turning Milk into Curd
The best irreversible chemical change example is the formation of curd from milk. It is effortless to make curd. Heat the milk until it is lukewarm and then add a drop or two of either buttermilk or lemon juice. Set it overnight and the following morning, the curd is ready.
This process is called curdling. When an edible acidic substance is added to milk, the milk thickens, forming curd. Thickening, also known as coagulation, gives curd its thick quasi-solid appearance.
In scientific language, when lactose reacts with water, it produces lactic acid. Lactose is a substance present in milk which is also known as the ‘Milk Sugar.’ The sour taste of curd is a result of lactic acid.
The equation for the conversion of lactose to lactic acid is given as:
Lactose(C12H22O11)+Water(H2O)→Lactic acid [4CH3CH(OH)COOH]
This reaction changes the chemical composition of milk altogether, and thus, it is an irreversible process.
Rusting of Iron
Another fine and important irreversible chemical change example is the rusting of iron. When iron associates with oxygen in the presence of moisture, it forms iron oxide and starts to rust. This reaction is well known as a redox reaction. In a redox reaction, one substance undergoes oxidation while the other undergoes reduction, and thus, the reaction is called a redox reaction.
Iron becomes crumbly and reddish-brown when rusted. Iron can be prevented from rusting but once rusted; it cannot be brought back to its original form.
Read more on Redox Reactions
Acid – Base Reaction
The reaction between an acid and a base is popularly known as neutralization. Here, let us take an example of ammonium bromide and potassium amide. Where ammonium bromide is an acid and potassium amide is a base. The reaction between an acid and a base invariably yields salt.
Ammonium Bromide(NH4Br)+Potassium Amide(KNH2)→Potassimum Bromide(KBr)+Ammonia(2NH3)
Salt is a neutral compound and in this case, potassium bromide is a salt. Acid is known for either donating its proton or for making covalent bonds. Here, it is a clear case of donating its proton.
Acids are wet or sticky and taste sour, while bases are slippery to touch and taste bitter.
One excellent example for both an acid and a base that we use in our regular life is vinegar, which is an acid, and baking soda, which is a base. These products are weak acids and bases. Other than a few regular products, one shouldn’t touch an acid or a base directly as they can damage the skin.
Growth of Plants and Animals
The growth of plants and animals isn’t an entirely chemical process; again, it is a mixture of biological changes as well as chemical changes, and thus, we call it a bio-chemical change. As described above, in the section – ripening of fruits and vegetables, various enzymes, organisms, chemicals work together for the growth of the body. Human beings, too, come under this category.
The process of cooking, eating, digesting and body converting that food into energy all these processes come under irreversible change. Unlike humans, animals don’t cook, but they do eat and digest. Their body converts the food into energy just like ours!
Plants have a whole other system of obtaining energy from water and sunlight. They use the light received from the sun to perform photosynthesis, make fruits, flowers, and vegetables and produce oxygen.
All these processes are excellent irreversible chemical change examples. Most of them occur in our day- to- day life, while others can be observed in laboratories.