Is it true that lighting a candle causes a chemical change?

A chemical change occurs when one substance combines with another, resulting in the formation of one or more new compounds. This is referred to as chemical synthesis or decomposition in general.

You might be wondering why I’m talking about chemical changes when we’re lighting a candle. Yes, I’ve been thinking about the same thing. But believe me when I say that this is a very hot topic among chemistry students and the general public.

One of the most significant words in chemistry is chemical change. However, some of you may find it challenging if you don’t understand what chemical change is.

Yes, burning a candle results in a chemical change since carbon dioxide, water vapours, heat, and light are all released. Furthermore, the transformation is irreversible because the original substance cannot be restored in any way. A chemical change is defined by the loss or gain of energy as well as the irreversible nature of the reaction. As a result, candle burning is a chemical change.

Let’s take a closer look at what a chemical change is.

What is the definition of a chemical change?

A chemical change is an irreversible process that involves the rearrangement of one or more substances and a change in their chemical characteristics or composition, with the development of at least one new product as a result.

The chemical change, also known as a chemical reaction, occurs when a substance combines with another substance or decomposes to generate new products.

Chemical changes are irreversible and permanent, therefore they can’t be reversed by changing or modifying the experimental modifications, unless they’re reversed by other chemical reactions.

A change in mass and energy occurs when a chemical change occurs. The mass of a substance gains or loses after a chemical transition. In addition, the breaking of some bonds in reactants and the creation of new ones in the product cause energy loss or gain.

Chemical changes include the burning of wood or paper, the sourness of milk, the burning of candles, the digestion of meals, and so on.

Chemical vs. Physical Alteration

A chemical change occurs when the chemical characteristics of the matter change, but a physical change occurs when the observable properties of the substance, i.e. the physical properties of the matter, change.

The physical change is accompanied by a change in molecular arrangement, which results in a state change. There are no new products generated, and the matter’s composition remains unchanged.

exactly the same In freezing water, for example, the molecular composition of ice is identical to that of water.

The following characteristics distinguish chemical changes from physical changes:

Physical ChangeChemical Change
The composition of a substance undergoing the physical change remains the same even on the rearrangement of molecules.The composition of the substance is entirely
changed during a chemical change resulting in
the formation of new products.
Physical change is temporary change and
therefore can be reversed.
The chemical change is permanent and
Only the physical properties are affected
during a physical change.
Both physical and chemical properties are
affected during a chemical change.
There is no change in the mass or energy of
the substance.
During a chemical change both mass and
energy is either gained or lost.
No new substance formation takes place.At least one new substance is formed due to chemical change
Some examples of physical change are
freezing of water, melting of wax, boiling of water, etc
A few examples of chemical change are
digestion of food, burning of coal, rusting, etc.

What Causes a Chemical Change When You Burn a Candle?

Because oxygen from the air mixes with carbon dioxide during combustion, the phenomena of burning a candle is a chemical change.

The fact that the burning of a candle is a chemical process reveals the creation of carbon dioxide that was previously absent.

The candle’s burning is eternal because it can’t be put back into the candle once it’s been extinguished. A new product is also created with a different composition than the candle. As a result, it’s a chemical change.

Burning is a chemical reaction that creates heat and light as a result of oxidation.

When a candle burns in the air, it reacts with oxygen, hydrogen, carbon, and other gases, increasing the product’s mass and causing carbon dioxide and water vapour to develop.

Why isn’t lighting a candle a physical alteration?

While the melting of wax occurs during the burning of a candle, the burning of a candle is a physical change.

The development of new products, as well as the discharge of heat and light, accompany the burning of candles.

There should be no formation of new products or release of energy for a reaction to be a physical change, yet this is not the case when a candle is burned. As a result, it demonstrates that the act of lighting a candle is not a physical change.

Though candle burning is not a physical change, the melting of wax is. When wax melts down as a result of candle burning, it retains its original makeup.

The mass of wax before and after melting is the same, and the wax solidifies the same way it did previously. As a result, the transformation is reversible, and the melting of wax is a physical transformation.

How Does a Candle Work?

Hydrocarbons, which comprise carbon and hydrogen, make up the majority of candles. Combustion is what keeps candles burning.

When the wick is lit, the melted wax is pushed up through capillary action towards the wick, which is a natural absorbent.

The wax is vaporised by the heat of the flame, and these gas molecules react with oxygen in the air to produce carbon dioxide, water vapours, heat, and light. Throughout the reaction, the wax serves as a source of energy.

CnH2n+1  +  O2  →  CO2  +  H2O  +  Heat  +  Light

More evaporation of the wax occurs as a result of the heat released, resulting in more combustion and the generation of carbon dioxide, water vapours, heat, and light in greater quantities. The combustion will continue until all of the wax has been burned.

Because it takes some time for the combustion to stabilise, you may see a flickering of flame or smoke while burning a candle at first.

The flame is divided into four separate coloured areas, each of which represents a different reaction.

The oxygen-rich innermost zone, where hydrocarbons vapourize into carbon and hydrogen, is blue in colour. Hydrogen reacts with air first, forming water vapour, while a little amount of carbon burns to produce carbon dioxide.

The second layer is the brown layer, which contains less oxygen and is where various other types of carbon break down and settle.

The next layer is the yellow-colored zone, which sees an increase in the creation of soot, or unburned carbon. Because this is the most visible part of a candle flame, the human eye perceives it as yellow.

The blue edge, which is the hottest zone of the flame, is the fourth and outermost region of the flame.

Take a look at this fascinating video about how candles work.

Is the reaction of a burning candle exothermic or endothermic?

Depending on whether energy is released or acquired, a reaction might be exothermic or endothermic.

An exothermic process is one that releases energy in any form, such as heat, light, or chemical energy. The energy of the products is always smaller than the energy of the reactants in exothermic processes.

The energy of the product is greater than the energy of the reactants in an endothermic reaction because energy is absorbed throughout the process.

The burning of a candle is an exothermic reaction because energy is released in the form of heat and light during the reaction.

The energy required to break the bonds in reactant molecules is less than the energy released during the formation of bonds in products, indicating that the reaction is exothermic.


Finally, we may state that the burning of a candle is a chemical process that results in the formation of new products. A chemical change occurs when new substances are formed, the mass and energy of the components change, and the reaction is irreversible.

All of these changes occur when a candle is burned, making it a chemical change. These qualities demonstrate that while candle burning cannot constitute a physical change, the melting of wax during candle burning can be.

In the presence of oxygen, a candle burns on the principle of combustion, where the wax vaporises and reacts with oxygen from the air to produce carbon dioxide and water vapours. Because energy is emitted in the form of heat and light, the burning of a candle is an exothermic reaction.

A chemical shift occurs when a candle is lit.

Good luck with your reading!!

Read more: Is SF6 a polar or nonpolar substance?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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