Chem Explorers

Spotting Chemical Changes: Signs and Types Explained

Chemical Change: A Guide to Understanding Inorganic, Organic, and Biochemical Reactions

Have you ever seen a nail rust? Or maybe you’ve witnessed the magic of bread rising.

While these two processes may seem unrelated, they are actually both examples of chemical changes. In this article, we will dive into the world of chemical changes, including inorganic, organic, and biochemical reactions.

By the end, you will have a better understanding of how certain chemical reactions occur and why they are important.

Inorganic Change

Inorganic chemical changes involve reactions that do not contain carbon. These can include acid-base reactions, neutralization reactions, combustion reactions, oxidation, and reduction.

Let’s look at some examples of each. Acid-base reactions occur when an acid (a substance with a pH lower than 7) and a base (a substance with a pH higher than 7) come together to form water and a salt.

One common example is the reaction between hydrochloric acid and sodium hydroxide, which can be written as:

HCl + NaOH NaCl + H2O

Neutralization reactions are a specific type of acid-base reaction where the acidic and basic properties are neutralized. For example, if you mix hydrochloric acid (HCl) with sodium hydroxide (NaOH), you get sodium chloride (NaCl) and water (H2O).

This is a neutralization reaction because the acidity and basicity cancel each other out, resulting in a neutral solution. Combustion reactions are perhaps the most well-known type of inorganic chemical change.

This is when a substance is burnt and reacts with oxygen, producing energy, heat, and often a flame. For example, when we burn propane gas (C3H8) in a grill, it reacts with oxygen in the air (O2) to produce carbon dioxide (CO2) and water (H2O):

C3H8 + 5O2 3CO2 + 4H2O

Oxidation is the process where a substance loses electrons, while reduction is when it gains electrons.

For example, when iron (Fe) rusts, it is oxidized as it loses electrons. On the other hand, in photosynthesis, plants reduce carbon dioxide, which means they gain electrons.

Organic Change

Unlike inorganic changes, organic chemical reactions involve carbon-containing substances. These can include combustion reactions, polymerization, condensation, fermentation, methylation, and halogenation.

Let’s take a closer look at some of these reactions. Combustion of natural gas is a largely organic chemical reaction that is used widely in natural gas cookers and heating systems.

This type of combustion reaction is exothermic, releasing energy in the form of heat. Frying an egg is another example of an organic change.

When an egg is heated, the proteins in the egg change shape and coagulate, or solidify. This is a result of the chemical reaction between the egg and heat.

Polymerization is the process where two or more monomers (small molecules) combine to form a larger polymer. One common example of polymerization is the creation of plastics.

For example, polyethylene is made up of many ethylene molecules polymerizing together. Condensation is another organic chemical reaction that occurs when two molecules combine to form a larger molecule, usually with a release of water as a by-product.

For example, when two amino acids react, they join together via a peptide bond to form a dipeptide, releasing water in the process. Fermentation is a type of organic change that occurs when microorganisms break down organic matter in anaerobic (oxygen-deprived) environments.

One common example of this is the fermentation of sugars in fruits and grains to produce alcohol. Methylation is the process of adding a methyl group (-CH3) to a molecule.

This type of organic change is common in biology and is important for controlling gene expression and metabolism. Halogenation is a type of organic chemical reaction where a halogen, such as chlorine or bromine, is added to a molecule.

This can result in changes in the properties of the molecule, such as making it more reactive.

Biochemical Change

Biochemical changes involve complex reactions that occur in living organisms. These include photosynthesis, digestion, and decomposition of organic matter.

Let’s examine these biochemical changes in more detail. Photosynthesis is the process by which plants, algae, and some bacteria convert sunlight into energy in the form of organic molecules, such as glucose.

This process involves many complex chemical reactions, including the conversion of carbon dioxide to glucose. Digestion is the process by which food is broken down in the body into components that can be absorbed and used for energy.

This involves many different types of biochemical changes, including the breakdown of carbohydrates, proteins, and fats. Decomposition of organic matter is a process that occurs naturally in the environment and is essential for recycling nutrients.

This involves the breakdown of complex organic molecules into simpler ones that can be taken up by plants and other organisms.


Understanding chemical changes, including inorganic, organic, and biochemical reactions, is essential for understanding many aspects of our world, including cooking, energy production, and biology. By knowing the types of chemical reactions that can occur and their mechanisms, we can better appreciate the vital role they play in our lives.

Signs of Chemical Change: Understanding the Different Clues of Chemical Reactions

Many chemical reactions happen around us without us even noticing. However, sometimes, these reactions exhibit various signs that indicate a chemical change has occurred.

In this article, we will delve into the different signs of chemical change, including changes in temperature, color, odor, formation of precipitate, and bubbles. By the end, you will have a better understanding of how to identify chemical changes around you.

Change in Temperature

One of the most noticeable signs of a chemical reaction is a change in temperature. A chemical reaction can be either exothermic or endothermic, which means it can release heat or absorb heat, respectively.

In exothermic reactions, the products have a lower energy state than the reactants, resulting in the release of energy, usually in the form of heat. An endothermic reaction, on the other hand, requires energy in the form of heat to proceed, so the reaction will feel colder.

An example of an exothermic reaction is a thermite reaction, which occurs when aluminum powder reacts with iron oxide to produce aluminum oxide and iron, as well as a lot of heat. This reaction is so exothermic that it is used for welding, cutting, and incendiary purposes.

Change in Color

Another sign of chemical change is a change in color. In some chemical reactions, the reactants have a different color compared to the products.

One example of this is rusting, which happens when iron reacts with oxygen in the presence of water, producing a reddish-brown color. Another example of a color change is the reaction between bleach and hair dye.

When bleach is used on hair, it causes a reduction reaction that removes the pigments from the hair shaft, resulting in a lighter coloring. If hair dye is added after the hair has been bleached, it will react with the residual bleach, resulting in a completely different color that can be lighter or darker than the original color.

Noticeable Odor

Chemical changes can also produce strong, noticeable odors. One excellent example of this is the decomposition of eggs.

Egg whites contain a protein called albumin, and when it breaks down, it produces hydrogen sulfide gas, which is a foul-smelling gas. This process starts to happen as soon as an egg is cracked open, although it may not be noticeable for some time.

Formation of Precipitate

A precipitate is a solid that forms in a solution during a chemical reaction. This is another sign of a chemical change, especially if the solution was previously clear or transparent.

For example, when silver nitrate (AgNO3) is mixed with sodium chloride (NaCl), it produces a white precipitate of silver chloride (AgCl).

Formation of Bubbles

The formation of bubbles is one of the most apparent signs of a chemical change. The bubbles are usually a result of a gas being produced during a reaction, such as carbon dioxide gas, which is produced when an acid reacts with a carbonate or a bicarbonate.

For example, when sodium carbonate (Na2CO3) is added to hydrochloric acid (HCl), carbon dioxide is produced, causing bubbles to form. The balanced reaction is:

Na2CO3 + 2HCl 2NaCl + CO2 + H2O

Another example of the formation of bubbles is the reaction between baking soda (sodium bicarbonate) and vinegar (acetic acid), which produces carbon dioxide gas, the bubbles causing the fizzy foam.


By understanding the different signs of chemical change, we can more easily recognize when a chemical reaction is happening. These signs include changes in temperature, color, odor, formation of precipitate, and the formation of bubbles.

Whether you are cooking, conducting experiments, or witnessing natural phenomena, an awareness of these signs can increase your understanding and appreciation of the chemical reactions that are happening around you. In this article, we have discussed the different types of chemical changes, including inorganic, organic, and biochemical reactions, and the various signs that indicate a chemical reaction has occurred.

These signs include changes in temperature, color, odor, formation of precipitate, and the formation of bubbles. Understanding these signs is essential in many fields, from cooking to biology, and can increase our appreciation of the chemical reactions happening around us.

Key takeaways include being observant, recognizing patterns, and being aware of the various signs of chemical change. FAQs:

Q: What are the different types of chemical changes?

A: The three types of chemical changes are inorganic, organic, and biochemical changes. Q: How do you identify a chemical change?

A: You can identify a chemical change through signs such as a change in color, temperature, odor, formation of precipitate, or the formation of bubbles. Q: What is an example of an inorganic change?

A: An example of an inorganic change is an acid-base reaction, such as the reaction between hydrochloric acid and sodium hydroxide. Q: What is an example of an organic change?

A: An example of an organic change could be the combustion of natural gas or the polymerization of plastics. Q: What is an example of a biochemical change?

A: An example of a biochemical change is photosynthesis or digestion. Q: Why is understanding chemical changes important?

A: Understanding chemical changes is important in many fields, such as cooking, energy production, and biology, as it allows us to recognize and appreciate the chemical reactions happening around us.

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