The burning of a candle is a chemical change. It involves a chemical reaction between the wax (hydrocarbons) and oxygen in the air, resulting in the production of carbon dioxide, water vapor, heat, and light. 1 The chemical composition of the wax changes as it reacts with oxygen to form new substances.
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Key Takeaways: Is Burning of Candle a Physical or Chemical Change?
- The burning of a candle is a chemical change because it involves a chemical reaction between the wax (hydrocarbons) and oxygen in the air, resulting in the production of carbon dioxide, water vapor, heat, and light.
- The chemical composition of the wax changes as it reacts with oxygen to form new substances.
- The burning of a candle is not considered a physical change because it involves a chemical reaction that results in the formation of new substances.
Why is burning of candle a chemical change?
The burning of a candle is considered a chemical change because it involves a chemical reaction known as combustion. 2 Combustion is a rapid chemical reaction between a fuel and an oxidizer (typically oxygen) that produces heat, light, and often other byproducts. 3
In the case of a candle, the fuel is the wax, which is usually made up of hydrocarbons, such as long-chain alkanes. 4 When the wick of the candle is lit, the heat of the flame melts the wax near the wick.
The liquid wax is then drawn up the wick due to capillary action. Once the liquid wax reaches the flame, it vaporizes and undergoes combustion.
During the combustion process, the hydrocarbons in the wax react with oxygen from the air, releasing energy in the form of heat and light.
The chemical bonds within the hydrocarbons are broken, and new chemical bonds are formed with oxygen to produce carbon dioxide (CO2) and water (H2O) as byproducts. These chemical changes are irreversible, meaning that the original wax cannot be recovered from the combustion products.
Therefore, because the burning of a candle involves a chemical reaction that results in the formation of new substances, it is considered a chemical change.
Why is burning of candle not a physical change?
The burning of a candle is not considered a physical change because it involves a chemical reaction that results in the formation of new substances. Physical changes typically involve alterations in the physical properties of a substance, such as its shape, size, or state, without any change in its chemical composition. 5
During the burning of a candle, the wax molecules undergo a chemical reaction with oxygen from the air, leading to the formation of carbon dioxide and water vapor.
The original wax molecules are broken apart, and new molecules are formed. These changes are not reversible, and the original wax cannot be recovered from the byproducts of combustion.
In contrast, physical changes do not involve the rearrangement of atoms or the formation of new substances. For example, melting the wax of a candle to change its state from solid to liquid is a physical change because the chemical composition of the wax remains the same.
The molecules are simply rearranged in a different state. However, when the candle burns, the chemical composition of the wax is altered, making it a chemical change rather than a physical one.
Further reading
Is Burning of Paper a Physical or Chemical Change?
Is Melting a Physical or Chemical Change?
Is Burning a Physical or Chemical Change?
Is Frying (or Cooking) an Egg a Chemical Change?
Is Cooking a Physical or Chemical Change?
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References
- UCSB Science Line. (n.d.). UCSB Science Line. http://scienceline.ucsb.edu/getkey.php?key=6845
- Combustion and Burning | Energy Foundations for High School Chemistry. (n.d.). Combustion and Burning | Energy Foundations for High School Chemistry. https://highschoolenergy.acs.org/how-do-we-use-energy/combustion-and-burning.html
- Combustion. (n.d.). Combustion. https://www.grc.nasa.gov/www/k-12/airplane/combst1.html
- Wax – Wikipedia. (2016, December 6). Wax – Wikipedia. https://en.wikipedia.org/wiki/Wax
- Physical change – Wikipedia. (2011, November 1). Physical Change – Wikipedia. https://en.wikipedia.org/wiki/Physical_change
