Substances around us undergo changes that may not be noticeable to us at all times. It is often difficult to classify them as physical and chemical changes. Regardless, both have major differences between them that might make it easy to understand the concepts. Furthermore, they might also help decipher each of them.
Physical vs Chemical Change
The main difference between physical and chemical change is that physical change is the process in which the state of matter of a substance changes even though the chemical composition remains intact. On the other hand, a chemical change is a process in which the chemical composition of a substance changes and often creates an entirely new substance.
When an object undergoes a physical change, there are noticeable differences in its appearance. The object however remains the same even though its physical properties are completely transposed. New energy is not produced during the process. Some examples of physical change include freezing of water, shaping of clay, and even chopping vegetables.
When an object undergoes a chemical change, an entirely new substance is created that now has a different chemical composition. Unlike the former, this kind of transposition is permanent. New energy tends to be produced during the process. Some examples of chemical change include rusting of iron, burning of coal, and cooking of vegetables.
Comparison Table Between Physical and Chemical Change
| Parameters of Comparison | Physical Change | Chemical Change |
| Definition | It is a process in which the physical properties of an object change while its chemical composition remains intact. | It is a process in which the chemical composition of an object changes entirely. |
| Effects | The appearance of the object changes. | The appearance of the object changes along with its chemical bonds. |
| Nature | It is a temporary change. | It is a permanent change. |
| Energy Production | New energy is not produced during the process. | New energy is produced during the process. |
| Energy Absorption | Very little to no energy is absorbed by the object. | A substantial amount of energy is absorbed, which then evolves. |
| Result | A new substance is not formed. | A new substance is formed. |
| Reversibility | It is easily reversible. | It is not reversible. |
| Examples | Some examples include freezing of water, shaping of clay, and chopping vegetables. | Some examples include rusting of iron, burning of coal, and cooking of vegetables. |
What is Physical Change?
Physical change is a process in which the physical properties of a substance change while its chemical composition is retained. As a result, the appearance and form of the substance change entirely. This includes its shape, size and in some cases even how it smells. When a substance undergoes the process, the result is generally reversible.
New substances with a different chemical composition are not formed after a physical change occurs. In fact, very little to no energy is absorbed during the process. Neither is any form of energy created. It is only that the state of matter of the substance changes from one form to the other.
A great example of a physical change is grinding a piece of wood into sawdust. Once the process has taken place, the result involves a change in appearance. Even though the state of the substance changes, the chemical composition of the wood remains the same. Moreover, there is no exchange, conversion or production of any kind of energy.
Other examples of physical changes include melting of ice, boiling of water, breaking a glass, tearing a paper bag, crumpling paper, chopping wood, mixing sand with water, mixing red stones with green coloured stones, and even cutting vegetables.
What is Chemical Change?
A chemical change is a process in which the chemical bonds in an object are broken, often to form an entirely new substance. It is often called a chemical reaction. Through the process, the appearance as well the chemical composition of the object change. The result is not reversible. A significant amount of energy is absorbed and produced during a chemical change.
After undergoing a chemical change, an entirely new substance is formed. The process may be organic, inorganic, or biochemical. An organic process is that which involves carbon. Inorganic changes do not involve or associate with carbon. Meanwhile, biochemical changes involve the chemistry of growth and survival of a living organism.
Some evidence of chemical changes includes a change of odour, emitted light or heat, creation of gases, decomposition of matter, formation of bubbles, change in temperature, and even change in colour. When any of these occur during say an experiment, it means that a chemical change has taken place.
Examples of chemical changes include food digestion, rusting of iron, cooking food, baking cookies, curdling of milk, wood burning in a furnace, ripening of fruits, fermentation, photosynthesis and even fire explosions. These bring a permanent change in the chemical composition of objects and create a new substance with a different chemical bond.
Main Differences Between Physical and Chemical Change
- Physical change is a process in which the physical properties of an object change while its chemical composition remains intact whereas chemical change is a process in which the chemical composition of an object changes entirely.
- Physical change brings a change in appearance whereas a chemical change brings a change in appearance and chemical bonds.
- Physical change is temporary whereas a chemical change is permanent.
- A physical change does not create new energy whereas chemical change creates it.
- A physical change involves little to no absorption of energy whereas a chemical change involves a significant amount of energy.
- A physical change does not create a new substance whereas a chemical change does.
- Physical change is easily reversible whereas a chemical change is irreversible.
- Examples of Physical change include freezing of water, shaping of clay, and chopping vegetables whereas examples of chemical change include rusting of iron, burning of coal, and cooking of vegetables.
Conclusion
Physical change and chemical change are majorly different from each other. A physical change involves a change in physical properties whereas a chemical change involves a change in chemical properties, as the name suggests. While Physical change changes the appearance of the substance, Chemical change changes appearance as well as chemical bonds.
There are various other differences as well in terms of production and absorption of energy. The most notable one is that Physical change is temporary and easily reversible whereas Chemical change is permanent and irreversible. It is fairly easy to understand and remember these concepts through examples. It is important to know these concepts while applying various fields of science.
References
- https://onlinelibrary.wiley.com/doi/abs/10.1002/jsfa.2740230406
- https://www.sciencedirect.com/science/article/pii/S0260877404003322