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Why Chemical Change Is Irreversible: Detailed Analysis

January 21, 2024November 29, 2021 by Durva Dave

The Chemical change is irreversible as new bonds are made.

When a chemical change occurs, the molecules present in one type of reactants break their bonds and make bonds with another kind of reactants, or they break bonds and create an entirely different molecule.

Due to this reason solely it is simple to understand why chemical change is irreversible. Though some chemical changes are reversible, that is because they have formed simple bonds that can be transformed back to the original. Whereas in irreversible chemical change, numerous complex changes occur that change the bond formation entirely, and it is impossible to reverse.

In this article, we shall have a close look at why chemical change is irreversible.

List of Contents

Creation of New Bonds

When two or more molecules react with each other, they create different types of bonds between them. These bonds, once created, are complicated to transform to the original. Though new molecules can be made by altering them, but they cannot be brought back to their initial state.

The molecules that react with each other are known as ‘Reactants,’ and the resultant molecules are known as ‘Products.’ Thus, in other words, reactants can be transformed into products, but products cannot be converted back to reactants.

Such equations are symbolized with an arrow that points in one direction.

Say, for example, reactant ‘A’ and reactant ‘B’ are made to react with one another, and they yield product ‘C’ and product ‘D,’ then the equation for this scenario is written as:

A+B→C+D

Why Chemical Change is Irreversible — **General Equation for Irreversible Chemical Changes**

Thus, the chemical properties of the material are altered entirely when such reactions occur. The change in chemical properties also changes the physical properties of a substance at times. Hence, such reactions are difficult to reverse, and in some cases, even impossible to reverse.

Have a look at Irreversible Chemical Change Examples

Baking a Cake

For instance, let’s take the example of cooking. Say a person is baking a cake. For making a cake, they will need flour, egg, butter, salt, sugar, milk, baking soda, water, and edible decorating ingredients.

First of all, all these ingredients will be mixed together. We can’t even begin to imagine the chemical processes taking place inside a material when nine ingredients are mixed all together. After the mixture, the cake is baked. Baking, frying, sautéing, etc., change the properties of a material to a whole another level.

Now, once the cake is baked, there’s no way we can transform the cake back to the nine initial ingredients that we used.

Change in Energy

One of the most essential reasons why chemical change is irreversible is the energy difference. As we saw above that a chemical change occurs when bonds are broken or created.

Sometimes, there isn’t enough energy present in the system that can reverse a reaction, or there isn’t enough energy in the system that can break all the bonds in the products.

Here, energy does not necessarily mean heat. Nucleus, atoms, and molecules altogether have energy and energy levels of their own. Providing them external heat just won’t make the expected change sometimes.

Elimination of Reactant

When a chemical reaction is performed in an open system, more often than not, some amounts of reactants are lost to the environment. For example, elimination of oxygen (O₂) or Carbon dioxide (CO₂) as they are in gaseous form.

If the closed system is not appropriately maintained, the gaseous reactants or resultant products can also blow off in an open environment. A system in which there is no transfer of matter or energy, neither from inside nor from outside, is known as a closed system.

Though there are different closed systems in which the transfer of either of them is allowed, like, in thermodynamics, where transfer of energy is allowed, but the transfer of matter is not permitted in a closed system.

Consecutive Reactions

The formation of Carbon Tetrachloride from Methane involves many steps. Methane is chlorinated in the presence of light to obtain chloromethane, which is again chlorinated in the presence of light, giving dichloromethane. Further chlorination yields chloroform, chlorination of which will result in Carbon Tetrachloride.

The equation of the reaction is given as:

Chlorine is added to the products, and light works as a catalyst.

The initial reactants are the same, but the process is lengthy. Reversing this process is usually difficult or sometimes even impossible.

In this case, only chlorine is added at every step. There are also some reactions that involve more than two reactants at every stage, which makes the process even more complex.

Products are More Stable than Reactants

In some reactions, products are more stable than the reactants, and thus, transforming the products back to reactants is exceptionally burdensome. The products have double or triple bonds formed on occasions, which are not easy to break or even reverse.

Exothermic reactions are said to be irreversible. For example, combustion; when a log of wood is set to fire, it releases energy in the form of heat and light. This energy is emitted out of the system, and thus, it is an exothermic reaction. Hence, the products yielded will be more stable than the reactants, which is why we cannot bring back wood from ashes.

Also Read:

Irreversible Chemical Change Examples: Detailed Analysis

January 20, 2024November 27, 2021 by Durva Dave

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.

Fuel(C_xH_y)+Oxygen(O₂)→Carbon Dioxide(CO₂)+Water(H₂O)

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.’

Irreversible Chemical Change Examples — **Ripening of Banana**
Image Credit : Shutterstock

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.

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.

Also Read:

Example Of Chemical Change Which Is Reversible: Detailed Analysis

January 20, 2024November 22, 2021 by Durva Dave

A reaction in which the conversion of reactants to products and vice-versa co-occur is known as a reversible reaction.

Mainly chemical change is irreversible, but various chemical reactions are reversible. One such easiest example of chemical change which is reversible is the Haber process.

In this segment, we will learn about various example of chemical change which is reversible.

List of Contents

The reaction between Copper Sulphate and Water

Copper sulphate exists in different colors with and without the presence of water; here, we will take the example of blue copper sulphate, which is hydrated and thus emits the color blue. When the hydrous copper sulphate and water are separated, copper sulphate becomes anhydrous, which simply means without water. This happens with the help of heating.

The crystal lattice surface of blue copper sulphate is surrounded by water molecules, these water molecules get banished as vapor when heated, and copper sulphate turns into a white solid.

Let’s have a look at the chemical reaction for the same:

This reaction between copper sulphate and water is an excellent example of chemical change which is reversible.

The reaction between Bismuth Oxychloride and Hydrochloric Acid

BiOCl – known as Bismuth (III) Oxychloride is dissolved in concentrated Hydrochloric acid, which yields Bismuth (III) Trichloride (BiCl₃) and water.

The reaction is given as:

When BiOCl is dissolved on HCl, a clear solution is formed, which means that the reaction is proceeding to the right side. When water is poured into this solution, a white precipitate is created, which means that the reaction is preceding back to the left side and BiOCl is yielded. When concentrated HCl is added to this solution, the reaction will proceed to the right side, producing BiCl₃.

This process can be repeated several times until equilibrium is attained. It is a concentration based example of chemical change which is reversible.

The reaction between Carbon and Water to manufacture Hydrogen

To obtain Hydrogen in pure form, water in gaseous form or rather steam, which consists of hydrogen, is made to react with carbon.

There are various ways to separate hydrogen from a mixture of H₂and CO, both in gaseous form.

To describe a few, one can be to heat this mixture at temperatures around -200°C. At this temperature, carbon monoxide will be liquefied and can easily be separated from hydrogen.

Another method can be to heat this mixture in the presence of iron. Carbon monoxide will react with iron and form rust, thus making it easy to carry off hydrogen.

Read more on Is Chemical Change Reversible

Formation of Zinc from Zinc Oxide

Carbon monoxide is made to react with zinc oxide. In this reaction, Carbon Monoxide will act as a reducing agent, which means that it will reduce oxygen from the subsequent reactant. As a result, we get zinc in solid form and Carbon Dioxide in gaseous form, making it easier to extract zinc.

Note:- The image provided above is just for reference and does not necessarily mean that zinc will appear to be like that when extracted.

The mixture of gaseous Hydrogen and vaporized Iodine

To obtain high purity samples of hydrogen iodide, a mixture of hydrogen and iodine, both in gaseous form, is heated at high temperatures around 443°C in a closed vessel for 2-3 hours. As a result, we obtain hydrogen iodide. When the mixture is heated again after the formation of hydrogen iodide, in the same manner, it decomposes back to gaseous hydrogen and gaseous iodine.

The reaction for the same is given as:

Initially, two iodine atoms dissociate and get attached on the side of two hydrogen atoms, and the bond looks somewhat like this: I—H—H—I, but as we know that hydrogen has only one valency to fulfill its outer shell, it will immediately break the bond with another hydrogen and form bond with iodine to become hydrogen iodide. This process happens in a fraction of microseconds, and it is difficult to capture the intermediate process.

Formation of Sulphur Trioxide from Sulphur Dioxide

Sulphur is found in the atmosphere, in rocks, in plants and innumerable other places. Oxygen – as we all know, is present in the environment, mainly in the air that we breathe. Thus, the reaction of sulphur with oxygen occurs naturally. When oxygen forms a bond with another element, that element is said to be oxidized, and hence the process is called oxidation.

So when sulphur is oxidized, it becomes sulphur dioxide. On further oxidation, it results in sulphur trioxide.

The forward reaction requires heat to process further, and thus, it is exothermic. When heat is provided, sulphur dioxide reacts with oxygen to form sulphur trioxide. Now, when the final product is kept down for cooling, sulphur trioxide will decompose into its original reactants. And hence, the reverse reaction is endothermic, as it emits the extra heat from the mixture.

The reaction for this process is given as:

Sulphur Dioxide(2SO₂)+ Oxygen (O₂) –> Sulphur Trioxide (2SO₃)

Is Chemical Change Reversible: Detailed Analysis

January 20, 2024November 16, 2021 by Durva Dave

‘Is chemical change reversible?’ – This question has been asked numerous times and left people scratching their heads.

The Chemical change is reversible at times. Yes, you read it right! Well, a chemical change is usually an irreversible process, but the beauty of chemistry is that – it has exceptions, just like this one.

The reversible chemical reaction has the ability to progress in both ways, which simply means to move forward as well as backward. But this process occurs only till dynamic equilibrium is attained. Equilibrium, in this case, is achieved when two reactions, happening in opposite ways, occur at the same time and at the same rate.

What is a Reversible Process?

Reactions that do not reach to the absolute completion are reversible.

A reversible process or reaction is a reaction in which reactants are converted into products and products are converted into reactants simultaneously.

On occasions, the number of reactants getting converted back from products might vary from the original amount of reactants.

Give some advantages and disadvantages of a reversible chemical reaction.

Advantages	Disadvantages
Reversible chemical reactions or in general, every chemical reaction help us in understanding the properties of matter and in developing new technologies or new products.	Occasionally, the produced outcome may be harmful to the environment as well as to the other life forms on earth (like humans, animals, plants, marine life, etc.).
Increased reaction rates.	They cost more in terms of both, money and time.
Improved quality of the product.	Finite applications.
Less initial investment.	Requirement of complex operations when wanting to reverse the reaction.
Simple reactant to a product mixture.	Quite a time, complex product to reactants conversion.
Finer product quality.	Considerable experimental development is required.
Enhanced catalyst life.	Only a few reactions can be reversed compared to more number of irreversible reactions.

Give one Example of Reversible Chemical Change.

The reaction of ammonia and hydrogen chloride is one such example of reversible chemical change.

Ammonium chloride, a mixture of ammonia and hydrogen chloride, which is a white solid. When hydrogen chloride and ammonia are mixed at room temperature, i.e., 25°C, they form ammonium chloride.

It again breaks down into ammonia and hydrogen chloride when heated.

Whenever a reversible chemical reaction takes place, a part of the reaction heading in one direction will always be exothermic, and the reaction heading in another direction will always be endothermic.

Remember, the reaction from left to right doesn’t need to be exothermic, and the reaction from right to left doesn’t need to be endothermic. It can occur in whichever way possible.

What should be the equilibrium position for a reversible reaction?

The equilibrium of a reversible chemical reaction is affected by several factors.

The reaction is in equilibrium when the concentration of reactants and products are equal.

One can change the equilibrium of a reversible chemical reaction through various other conditions like adjusting the temperature, changing the pressure, changing the concentration, etc.

Let us consider a straightforward example to understand the concentration of a reaction with the help of the Haber process.

Say, one part of nitrogen molecules and three parts of hydrogen molecules are mixed together to get two parts of ammonia molecules.

Now, when we say one part means 1 N₂ molecule and not 1 N, as Nitrogen (N) alone cannot exist. A single nitrogen atom immediately makes a bond with another nitrogen molecule to fulfill its valance band.

Similarly, three parts of hydrogen mean 3 H₂ molecules.

Thus, the reaction for the Haber process is given as follows:

Now the question arises that 1N₂+ 3H₂should yield 4NH₃ but instead, we have 2NH₃.

Well, when looked closely, there are 2 N molecules on the left side as well as 2 N molecules on the right side.

Similarly, for hydrogen on the left side, we have 3H₂molecules, which give 3×2 = 6 hydrogen atoms as well as 3×2 = 6 hydrogen atoms on the right side.

When the numbers of atoms or molecules on both sides are equal, the reaction is said to be balanced, and hence, we can say that it is in equilibrium.

is chemical change reversible — General Chemical Reversible Reaction

Examples of Reversible Chemical Reaction

Haber process.

Formation of Hydrogen Iodide.

Decomposition of Calcium Carbonate.

The reaction of bromine with water.

The reaction of iron ions with thiocyanate ions.

Also Read:

How Chemical Change Occurs: Detailed Analysis

January 21, 2024November 11, 2021 by Durva Dave

Chemical Changes occur when a new bond between molecules is either formed or broken. This change results in new and different kinds of properties than the parent molecule.

When a chemical change occurs, there is rearrangement of atoms which changes the chemical composition of the substance as a whole, due to which this process is generally irreversible. When multiple compounds react with one another, two types of changes can be observed, one is the chemical change, and another is the physical change.

How chemical change occurs is a question asked frequently.

In physical change, no bonds are broken or formed. Thus, physical change can be observed when there is a change in state of the material, i.e., solid, liquid or gaseous form, physical deformation, etc.

Chemical change is when the internal composition of the matter changes, which results in change in color, change in odor, change in melting and boiling points, formation of precipitate, formation of bubbles, release of gases, change in composition etc. One of the significant points is, if the reaction is difficult to reverse or impossible to reverse.

Energy is always required to put forward a chemical reaction. Sometimes, the energy is absorbed by the molecules to carry forward the reaction and sometimes, energy is released.

Factors like temperature, presence of catalysts, concentration of the reactants, presence of moisture (for some reactions), state of reactants (solid, liquid, gas, and ions), etc., affect the reaction rate.

In this section, we will learn about how chemical change occurs, factors affecting chemical change, requirements for a chemical change to occur, types of chemical change, etc.

1. How Chemical Change Occurs?

When chemical change occurs, a substance is transformed into a different substance.

Chemical change occurs when the bond between two or more reactants is created, broken or simply rearranged.

Energy is required for both breaking and creating a bond. Sometimes, the energy needed to break the bond is higher than the energy required in making a bond. This binding or splitting changes numerous properties of the substance such as odor, color, state, melting point, boiling point, taste, etc.

For E.g.:- Rusting of iron is an example of chemical change as the iron reacts with oxygen and water and a different substance is formed, which is rust while boiling of water is not a chemical change as the water molecules only change their state (i.e., from liquid to gaseous) but not its form.

Chemical change is usually irreversible but in some cases, it is reversible too!

Similarly, physical changes are reversible but in some cases, irreversible too.

For E.g.:- Tearing off a paper is a physical act or change but it cannot be reversed. Even if we try to join the paper with different means, it won’t come back to its original form.

2. Why are chemical reactions important?

Chemical Change assists us in understanding the properties of matter.

Chemical changes help us understand the processes happening all around the world as well as in the universe.

Every action that occurs in the universe is a result of chemical change. Once the properties of matter are understood, one can also understand how to control a reaction. All this information helps in recognizing the ongoing processes and in developing or inventing new things.

3. Which is the most crucial chemical change?

The basic necessity for all life forms to survive in the biosphere is oxygen and food.

Photosynthesis was chosen as the most crucial chemical change in 1988.

Though humans, animals or other organisms do not perform photosynthesis on their own, they highly depend on plants (who carry out photosynthesis) for food and oxygen.

4. What are some examples of chemical change observed in everyday life?

One of the best and the most straightforward examples of chemical change that we observe in our day-to-day life is cooking.

Various physical and chemical changes take place when food is cooked. Another easy example is combustion.

Nowadays, the electric gas stove has taken over, but a large part of the world still uses the conventional gas stove that utilizes fire. Fire is nothing but a type of chemical reaction.

How Chemical Change Occurs — Examples of Chemical Change

5. Are all chemical changes Irreversible?

Not all chemical changes are irreversible.

Yes, you read it right; some chemical changes are reversible like, the Haber process.

In Haber process, hydrogen and nitrogen combine to form ammonia, which can later be separated into hydrogen and nitrogen again.

But this happens only till equilibrium is reached. Once the equilibrium is reached, the reaction cannot be carried forward or backwards.

6. Is mass conserved in a chemical reaction?

No, the mass is not conserved in a chemical reaction.

Yet, sometimes it is, but most of the time, it is converted into energy.

According to the famous equation given by Einstein, which states that mass can be converted into energy and energy can be converted into mass. The equation is given as:

E = mc²

Where, E = Energy; m = mass; c = speed of light in vacuum

More often than not, the mass converted into energy is in a negligible amount in atomic reactions. In nuclear reactions, the energy absorbed or released is relatively high, and thus, the change in mass is significantly visible.

7. What are the different types of chemical changes?

The different types of chemical changes are:

Organic Chemical Changes
Inorganic Chemical Changes
Biochemical changes

The organic type of chemical change deals with the chemistry of carbon, and the inorganic type of change deals with the chemistry of all the other elements and their compounds other than carbon. In contrast biochemical change involves the chemistry of the living organisms controlled by proteins and enzymes.

Also Read:

Chemical Change Examples: Detailed Analysis

January 20, 2024November 4, 2021 by Durva Dave

Chemical changes generally happen when two substances react or combine with each other to form a different substance.

When any two or more substances in matter react with one another, two kinds of changes occur: Physical change which is usually reversible and chemical change which is generally irreversible. In this section, we’ll try to understand in detail about the chemical changes taking place in matter and the chemical change examples.

Irreversible processes are the processes in which the matter cannot be brought back into its initial form as the molecular structure of the matter partially or entirely changes.

Properties of chemical change

We can determine if the matter has gone through a chemical change or not with the help of the following properties:

If the molecular composition of the matter/ substance changes.
If the light is produced.
If there is a change in temperature of the matter as energy is either released or absorbed when changes in molecular composition occur.
When the energy is released, it is known as an exothermic reaction.
When the energy is absorbed, it is known as an endothermic reaction.
If the sound is produced.
If there is a change in mass of the reactants present in the substance.
If there is a change in composition.
If gas is produced.
If the color of the substance changes.
If a precipitate is formed.
In the case of liquids, bubbles may form.
If an odor is released.
If the change is difficult to reverse or impossible to reverse.

A chemical change might not display all the signs, but a few are likely to occur.

Types of chemical change

The types of chemical changes are divided into three main categories:

Organic changes
Inorganic changes
Bio-chemical changes

Further, let us have a close look at these three changes:

1. Organic Changes

‘Carbon’ – one of the most important components of organic chemistry and hence the organic change.

Changes concerned with the chemistry of carbon and elements or compounds with which it reacts are known as Organic Chemistry.

Thus, when a substance undergoes a change involving carbon and its compounds, it is known as organic chemical change or simply organic change.

Some typical examples of organic changes involve:

Cracking of hydrocarbons from crude oil for making gasoline at an oil refinery.
Halogenations, which means reactions that deal with elemental halogens like Fluorine (F), Chlorine (Cl), Iodine (I), Bromine (Br), etc.
Condensation reaction in which a single molecule is formed from the combination of two or more molecules. Usually, there is a loss of water when this type of reaction occurs; it is known as condensation reaction.
Methylation, which means adding a methyl group to a substrate.
Polymerization, which includes the reaction of monomer molecules to form a polymer chain in 3-dimensional networks.

2. Inorganic change

Reactions that do not involve ‘carbon’ are known as inorganic reactions and hence inorganic chemical change or simply inorganic change.

The typical types of reactions that inorganic changes involve are:

Mixing of acid with a base, generally known as neutralization.
Redox reactions in which there is a shift in oxidation states of atoms due to oxidation or reduction.
Decomposition reaction in which a compound breaks down into two or more substances.
Displacement reactions in which an atom or ion of one compound replaces an atom or ion of another compound.

3. Biochemical Change

It is a chemistry that occurs in living organisms such as plants, animals, humans, microorganisms, etc., where enzymes and proteins control most reactions.Biochemical change is highly complex, and it is still not fully understood.

Typical types of biochemical changes involve:

Photosynthesis is a process used by plants, algae, and cyanobacteria (a group of bacteria) to convert light energy that is generally received from sunlight to convert into chemical energy so that it can be later used to fuel the organism’s activities.
Protein synthesis, which creates protein in molecules that helps in the growth of the organism.
Krebs cycle, which is a process that releases stored energy derived from proteins, fats, and carbohydrates through oxidation.
Digestion is a process in which large food molecules are broken down into small food molecules so that they can be absorbed into blood plasma which helps the body to move and grow.

Chemical Change Examples

1. Rusting Iron

Rusting is a chemical process that happens when iron or its alloys come in contact with oxygen in the presence of moisture, and hence it is a type of Redox reaction known as oxidation.

Iron(Fe)+Oxygen(O)+Water(H₂O)=Hydrated Iron(III)Oxide

Objects submerged in the sea tend to rust faster due to the presence of salt in the seawater through the electrochemical process.

As rusting is a type of irreversible chemical change, iron cannot be brought back into its original form, but it can sure be prevented from rusting by using non-rusting materials or slow rusting materials as a protective coat on deteriorating materials, by galvanizing the material, or by coating the material by painting, wax tapes, varnish, and lacquer.

iron rust — Iron Rusting
Image Credit: flickr

2. Cooking Food

Cooking food is the simplest example of chemical change. For cooking any food, the raw ingredients are either boiled, fried, baked or sautéed. In any case, there is a change in its chemical composition, which cannot be reversed back. When the raw ingredients are cooked, there is a change in flavor, color, nutritional composition, etc.

3. Digestion of food in the stomach

When the food that we eat reaches the stomach, it mixes with several digestive juices and enzymes that the stomach makes. The stomach’s strong muscles blend the food with enzymes and digestive juices to turn the food into a usable form. Once this process is completed, the food slowly enters the small intestine via a short tube between the stomach and the small intestine. Here the next step takes place when the juices produced in the pancreas and liver turn the food into energy. As a result, a lot of processes take place that completely change the food’s chemical composition. And thus, digestion of food is a chemical change.

4. Burning wood

Burning of wood is an example of chemical reaction as the structure and chemical composition of the wood change as a whole. Oxygen is an essential component when it comes to igniting something. In the absence of oxygen, the material would not catch fire or would not get ignited. So, when the wood log is kindled, it turns into ashes releasing carbon dioxide and water vapor.

wood burning — Wood Burning
Image Credit: flickr

5. Fruit/Vegetable getting rotten

There are multiple reasons behind fruit/vegetables or any food getting rotten, such as prolonged exposure of food in closed spaces in the presence of moisture, fermenting, acidifying, etc. Such processes create bacteria and fungi that sometimes cannot be harmful themselves, but their waste products may cause severe implications to one’s health.

a rotten capcicum — A rotten Capsicum
Image Credit: flickr

6. Decomposition of matter into the soil

Decomposition is a process that breaks down large pieces of matter into smaller ones. It is affected by several factors such as the soil’s surface, temperature, accessibility to flies or insects, oxygen, humidity, composition, and the matter’s internal components. The rate of decomposition also varies due to all such factors.

7. Firecrackers

Various chemical powders are filled inside a firecracker, which, when set to fire, react with each other producing different types of sound, color, lighting and patterns. For a firecracker to burn with its expected result, it needs some amount of energy known as Activation Energy . Once the tip of the firecracker is ignited, heat is produced that provides the required activation energy to the firecracker to show its beautiful result in the form of lighting and color.

Still, with this stunning effect, there comes a severe issue, that is the release of toxic chemicals into the atmosphere such as carbon monoxide, potassium, nitrogen, carbon dioxide, ammonia, etc., that create air pollution, which in turn has adverse effects on human health, animals and plants. Also, various institutions are researching to make an Eco-friendly alternative to firecrackers.

8. Photosynthesis

Photosynthesis is a process used by plants and other organisms to convert light energy received from sunlight into chemical energy that can further fuel the body’s movement and growth. This energy is stored in starch and sugars present in the particular body. Plants absorb Carbon Dioxide and water from the surrounding environment like air and soil and, in turn, emit oxygen in the presence of light which acts as a catalyst.

A general equation for photosynthesis in plants is given as:

A light-absorbing pigment known as chlorophyll, responsible for giving the green colour in plants absorbs energy from blue-light and red-light and reflects the green-light, making the plant appear green.

Thanks to plants for which oxygen is a waste, due to which all life forms on earth can breathe.

9. Leaves changing color

Many factors affect the change in color of leaves. One such is the breaking down of chlorophyll pigments, due to which plants lose their green color. When chlorophyll breaks down, another pigment known as Anthocyanin, responsible for the red color in leaves, comes to the rescue that protects the leaves from harmful sun-rays. But this doesn’t last for an extended period of time; eventually, these leaves dry out and fall off. Similarly, different pigments are responsible for different colors in plants.

Some other reasons for leaves changing color are drought, disease, change in the soil pH level, too little or too much availability of water and root damage.

10. The reaction between acid and base

The reaction between acid and base is referred to as Neutralization. It can be used to determine the pH level of a substance.

When neutralization takes place, the resultants come out as a mixture of salt and water.

Acid + Base→Salt + Water

One of the most famous and easy examples of this reaction is the mixture of Hydrochloric acid with Sodium Hydroxide, which is a base, both in aqueous form, that yields Sodium Chloride and water.

Its reaction can be given as follows:

Hydrochloric Acid (HCL) + Sodium Hydroxide (NaOH)→Sodium Chloride (NaCl) + Water(H2O)

The reaction between an acid and a base is one of the most important chemical change examples.

Also Read:

Change	Equilibrium
Pressure Increased	Moves to fewer molecules
Concentration Increased	Moves to the opposite direction from that reactant
Temperature Increased	Moves to the endothermic reaction