Difference Between Physical and Chemical Change - Definition, Characteristics, Examples, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:30 PM IST

Matter undergoes two different types of changes in nature: physical and chemical change. A physical change would affect a material's physical characteristics, while a chemical change impacts the chemical properties, as its names suggest. Many physical changes including heating and cooling are recoverable, whereas chemical changes are irreparable or only reversible with another chemical process.

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Definition of Physical Change :
Definition of Chemical Change :
Characteristics of physical change:
Characteristics of chemical change:

Difference Between Physical and Chemical Change - Definition, Characteristics, Examples, FAQs

Definition of Physical Change :

Physical transformation or change is a result in which a substance's physical qualities, such as shape, size, quantity, appearance, colour, state (i.e., solid, liquid, gas), and so on, change without affecting its molecular composition. These changes are inherently unstable, but they can be reversed with basic physical techniques. The same component or combination exists before or after the alteration, i.e. the object's fundamental physical appearance is preserved. Examples of physical changes comprises, wax melting, glucose dissolving in water, water bubbling, wood cutting, paper crumpling, and so on.

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Definition of Chemical Change :

Chemical change is explained as the method of rearranging or combining the molecules of one or even more substances to generate a new component. When a substance undergoes chemical transformation, its molecular character changes, and this is transformed into a new substance with a specific chemical structure. The development of energy, the formation of bubbles, and temperature variations are all examples of chemical change.

Alternatively, chemical change is called as a chemical reaction, in which the chemicals involved are referred to as reactants, as well as the reaction's outcome is referred to as a product. Because of the creation of the entire product, energy change is one of the characteristics of a chemical change. It is impossible to reverse the chemical change once it has occurred. For example, bleaching a stain, combining vinegar and baking soda, and so forth.

Common Physical Changes :

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Texture:

A physical alteration can modify the smoothness of a substance. A piece of wood that has been sanded, oiled, and polished, for example, will have a very different appearance than it had when it was rough.

Colour:

A substance's colour changing isn't always an indication of a chemical change. Changing the colour of a metal, for example, has no effect on its physical qualities. A colour change, on the other hand, is frequently an indication that a chemical reaction is taking place. The nature of the metallic component is not changed by painting the metal car whereas the physical appearance is altered.

Temperature:

Even though we cannot see change in temperature, it is a physiological response unless a change of condition occurs.

Shape:

An entity's shape can be modified while the object's molecular structure remains unchanged.

Change of state:

A physical change occurs when a substances changes its state. A multitude of physical qualities, such as viscosity and form, are changing in this scenario. When ice melts into water, it loses its solid form and becomes a viscous fluid.

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The common physical changes of state are:

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Common Chemical Changes :

Change in Temperature

Variation in temperature is major characteristic of a chemical change.

Change in colour:

Another sign that a chemical reaction is currently happening is a change in colour. For instance, observing the rusting of metal over time will reveal that the metal has changed colour and glowed yellow. This colour shift is the result of a chemical process.

Odor development:

A chemical reaction occurs when two or more chemicals or components are combined, and a fragrance or odor is produced. A chemical reaction has occurred when an egg begins to smell (a rotting egg, for example). A chemical decomposition has resulted in this.

Formation of precipitate:

One of the most common signals that a chemical reaction is taking place is the emergence of a precipitate. A precipitate is a substance that develops inside another solid or within a solution.

Characteristics of physical change:

Properties of physical change has three characteristics:

There is no formation of a new material.
The modifications are recoverable.
Both the product and the reactant have the same physical characteristics.

Characteristics of chemical change:

Properties of chemical change has four major characteristics:

A chemical reaction results in the formation of a new material.
The alterations are long-term.
The change is usually irreversible.
It also entails the absorption or release of energy, such as heat or light.

What is the difference between physical and chemical change?

Distinguish between physical and chemical change
PHYSICAL CHANGE	CHEMICAL CHANGE
The molecules are reconfigured because of a physical change, but their true composition stays unchanged.	A chemical change causes a substance's atom configuration to totally change, resulting in the formation of a new compound.
Physical change is only a short term transformation	A chemical change is a long-term transformation.
Only physical properties, such as shape and size, are affected by a physical change.	Chemical changes the substance's physical and chemical qualities, as well as its makeup.
A physical change includes little or no heat transfer.	Absorption and development of energy occur during a chemical process.
Physical changes include the freezing of water, the melting of wax, the boiling of water, and so on.	Food digestion, coal combustion, corrosion, and other chemical changes are examples.
Physical changes, in definition, do not necessitate the creation of energy.	The creation of energy is frequently involved in chemical transformations (which can be in the form of heat, light, sound, etc.)
A physical change does not result in the formation of a new material.	One or even more new substances are always present when a chemical transition occurs.
The physical change is reversible, which means the original material can be retained.	Chemical transformations are irreversible, which means that the original component cannot be restored.
The molecules are reconfigured during a physical change, but their true composition remains unchanged.	A chemical change causes a substance's atom configuration to totally change, resulting in the formation of a new compound.

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The above table shows the difference between physical change and chemical change.

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Frequently Asked Questions (FAQs)

1. What is physical change?

2. What is chemical change?

3. Give an example for a chemical change having an odour development.

Chemical change is usually accompanied by a change in colour, evolution of gas or formation of precipitate or the development of an odour. Rotting of eggs is an example for a chemical change having odour development.

4. Write the difference between physical and chemical change

Physical change is only a short-term transformation whereas a chemical change is a long-term transformation. Only physical properties, such as shape and size, are affected by a physical change while in Chemical changes the substance's physical and chemical qualities, as well as its makeup. A physical change includes little or no heat transfer, but absorption and development of energy occur during a chemical process.

5. Give a physical and chemical changes examples.

The example of physical change and chemical change are

Chemical change: rusting of iron.

Physical change: melting of ice.

6. Why is burning a piece of paper considered a chemical change?

Burning paper is a chemical change because it involves a chemical reaction between the paper (cellulose) and oxygen in the air. This reaction produces new substances (carbon dioxide, water vapor, and ash) with different chemical properties than the original paper. The process is irreversible, and the original paper cannot be recovered from the products.

7. What is the significance of reversibility in distinguishing between physical and chemical changes?

Reversibility is a key factor in distinguishing between physical and chemical changes. Physical changes are generally easily reversible through simple means, such as changing temperature or applying mechanical force. Chemical changes, on the other hand, are typically irreversible or require significant energy input to reverse. This difference arises from the fact that chemical changes alter the fundamental structure and bonding of substances.

8. How do physical and chemical changes affect the molecular structure of substances?

Physical changes do not alter the molecular structure or chemical composition of a substance. The molecules remain intact, but their arrangement or physical state may change. In contrast, chemical changes involve breaking and forming chemical bonds, resulting in a rearrangement of atoms and the creation of new molecular structures with different properties.

9. How do physical and chemical changes affect the energy content of substances?

Physical changes typically involve relatively small changes in energy content, usually associated with changes in intermolecular forces or kinetic energy of particles. Chemical changes, however, can involve significant changes in energy content due to the breaking and forming of chemical bonds. This can result in the release of energy (exothermic reactions) or the absorption of energy (endothermic reactions) from the surroundings.

10. How does energy play a role in physical and chemical changes?

Energy is involved in both physical and chemical changes, but in different ways. Physical changes often involve changes in the kinetic energy of particles or phase transitions, which require energy input or release. Chemical changes involve breaking and forming chemical bonds, which can either release energy (exothermic reactions) or absorb energy (endothermic reactions) from the surroundings.

11. Why is the melting of ice considered a physical change despite the dramatic change in appearance?

The melting of ice is considered a physical change because it only involves a change in the physical state of water from solid to liquid. The chemical composition and molecular structure of water (H2O) remain unchanged throughout the process. The dramatic change in appearance is due to the rearrangement of water molecules from a rigid crystal structure to a more fluid arrangement, not a change in their chemical nature.

12. What is the relationship between physical changes and the states of matter?

Physical changes are closely related to the states of matter (solid, liquid, gas, and plasma). Many physical changes involve transitions between these states, such as melting, freezing, evaporation, condensation, and sublimation. These changes occur due to variations in temperature and pressure, which affect the kinetic energy and arrangement of particles without altering their chemical composition.

13. What role do physical changes play in the preparation of chemical reactions?

Physical changes often play a crucial role in preparing substances for chemical reactions. For example, grinding solids into powders increases their surface area, which can significantly increase the rate of chemical reactions. Similarly, heating or cooling substances can change their physical state, making them more reactive or easier to mix with other reactants.

14. Why is it important to distinguish between physical and chemical changes in environmental science?

Distinguishing between physical and chemical changes is crucial in environmental science for understanding and addressing pollution, climate change, and ecosystem dynamics. Physical changes, like the melting of polar ice caps, can be potentially reversible with proper interventions. Chemical changes, such as the formation of acid rain or the depletion of the ozone layer, often have more lasting impacts and require different mitigation strategies. This distinction helps in developing appropriate environmental policies and conservation measures.

15. How do physical and chemical changes differ in their energy requirements?

Physical changes typically require less energy than chemical changes. Physical changes often involve overcoming intermolecular forces or changing the kinetic energy of particles, which generally requires less energy. Chemical changes, on the other hand, involve breaking and forming chemical bonds, which usually require or release larger amounts of energy. This difference in energy requirements is why chemical changes are often more difficult to reverse than physical changes.

16. What role do physical and chemical changes play in the water cycle?

The water cycle involves both physical and chemical changes. Physical changes dominate, including evaporation, condensation, and freezing of water. These changes allow water to move between different reservoirs on Earth. Chemical changes also occur, though less prominently, such as the dissolution of minerals in groundwater or the formation of acid rain. Understanding both types of changes is crucial for comprehending the complete water cycle and its environmental impacts.

17. How do physical and chemical changes affect the properties of materials in engineering applications?

In engineering, both physical and chemical changes are utilized to manipulate material properties. Physical changes, like heat treatment or mechanical processing, can alter a material's strength, ductility, or conductivity without changing its chemical composition. Chemical changes, such as alloying or surface treatments, can create materials with entirely new properties, such as increased corrosion resistance or altered electrical characteristics. Engineers must understand both types of changes to design and manufacture products with desired properties.

18. What role do physical and chemical changes play in the process of digestion?

Digestion involves both physical and chemical changes. Physical changes occur first, such as chewing food (mechanical breakdown) and mixing it with saliva. These changes increase the surface area of food particles, facilitating subsequent chemical changes. Chemical changes then occur through enzymatic reactions that break down complex molecules into simpler ones. For example, proteins are broken down into amino acids, and carbohydrates into simple sugars. This combination of physical and chemical changes is essential for efficient nutrient absorption.

19. Why is rusting considered a chemical change, and what factors accelerate this process?

Rusting is a chemical change because it involves the reaction of iron with oxygen and water to form a new substance, iron oxide (rust). This process changes the chemical composition and properties of the original iron. Factors that accelerate rusting include exposure to moisture, oxygen, salt, and acidic environments. Higher temperatures and the presence of electrolytes can also speed up the rusting process by facilitating the electron transfer necessary for the chemical reaction.

20. How do chemical changes contribute to the formation of new materials in industry?

Chemical changes are fundamental to the production of new materials in industry. They involve reactions that transform raw materials into products with different properties and applications. For example, the production of plastics involves chemical changes that polymerize simple molecules into long chains with unique characteristics. Similarly, the steel industry relies on chemical changes to alloy iron with carbon and other elements to create stronger, more durable materials.

21. How do physical and chemical changes contribute to weather phenomena?

Weather phenomena involve both physical and chemical changes. Physical changes include the evaporation and condensation of water, leading to cloud formation and precipitation. Wind is also a result of physical changes due to temperature and pressure differences. Chemical changes contribute to weather through processes like the formation of ozone in the atmosphere or the chemical reactions involved in acid rain formation. Understanding both types of changes is crucial for accurate weather prediction and climate modeling.

22. Why is cooking food often a combination of physical and chemical changes?

Cooking food typically involves both physical and chemical changes. Physical changes occur when food is cut, mixed, or heated, altering its shape, size, or state. For example, melting butter or boiling water are physical changes. Chemical changes happen when heat causes molecules in the food to break down or recombine, creating new flavors, colors, and textures. For instance, the browning of meat (Maillard reaction) or the caramelization of sugars are chemical changes. This combination of changes is what makes cooking a complex and interesting process.

23. How do physical and chemical changes affect the recycling process of materials?

In recycling, both physical and chemical changes play important roles. Physical changes are often used in the initial stages of recycling, such as melting plastics or crushing glass, which alter the form but not the chemical composition of the materials. Chemical changes are employed in more advanced recycling processes, like breaking down polymers into their constituent monomers or chemically treating materials to remove impurities. Understanding these changes is crucial for developing efficient recycling methods and determining which materials can be effectively recycled.

24. How do physical and chemical changes differ in their effects on the atomic structure of substances?

Physical changes do not affect the atomic structure of substances. The atoms and molecules remain the same, only their arrangement or state changes. In chemical changes, the atomic structure is altered as atoms are rearranged, bonds are broken and formed, and new substances with different atomic compositions are created. This fundamental difference is why chemical changes result in new substances with different properties, while physical changes only alter the form of the original substance.

25. What is the significance of physical and chemical changes in the formation of sedimentary rocks?

The formation of sedimentary rocks involves both physical and chemical changes. Physical changes occur during erosion, transportation, and deposition of sediments, altering their size, shape, and arrangement. Chemical changes take place during diagenesis, where minerals dissolve, precipitate, and recrystallize, cementing the sediments together. Some sedimentary rocks, like limestone, can also form through chemical precipitation. Understanding these changes is crucial in geology for interpreting Earth's history and the formation of natural resources.

26. What is the fundamental difference between a physical change and a chemical change?

A physical change alters the form or appearance of a substance without changing its chemical composition, while a chemical change results in the formation of one or more new substances with different chemical properties. In physical changes, the original substance can usually be recovered, whereas in chemical changes, the process is typically irreversible.

27. How can you distinguish between a physical and chemical change in everyday life?

You can distinguish between physical and chemical changes by observing key indicators. Physical changes often involve changes in state, shape, or size without altering the substance's identity. Chemical changes typically involve the production of heat, light, gas, color changes, or the formation of a precipitate. For example, ice melting is a physical change, while rusting of iron is a chemical change.

28. Can a change be both physical and chemical simultaneously?

While most changes are primarily either physical or chemical, some processes can involve both types of changes occurring simultaneously or in quick succession. For example, when you cook an egg, the initial heating causes a physical change (liquid becoming solid), but it also triggers chemical changes in the egg's proteins, altering their structure and properties.

29. Why is dissolving sugar in water considered a physical change, while dissolving an antacid tablet is a chemical change?

Dissolving sugar in water is a physical change because the sugar molecules simply spread out in the water without changing their chemical structure. The process is reversible by evaporating the water. Dissolving an antacid tablet, however, involves a chemical reaction between the tablet's components and water, producing new substances (often releasing carbon dioxide gas). This process is irreversible and results in new chemical compounds.

30. How do physical and chemical changes differ in their effect on the mass of a closed system?

In a closed system, physical changes do not alter the total mass of the system, as no matter is created or destroyed. The mass is conserved even if the substance changes form or state. In chemical changes within a closed system, the total mass also remains constant (law of conservation of mass), but the distribution of mass among different chemical species changes as new substances are formed and others are consumed.

31. How do catalysts affect chemical changes without undergoing permanent change themselves?

Catalysts facilitate chemical changes by lowering the activation energy required for a reaction to occur. They participate in the reaction by forming temporary intermediate compounds, which then break down to release the catalyst unchanged at the end of the reaction. This allows catalysts to speed up chemical changes without being consumed in the process, making them efficient in industrial and biological processes.

32. How do physical and chemical changes differ in their effects on the properties of polymers?

Physical changes in polymers typically affect their macroscopic properties without altering their chemical structure. For example, heating a thermoplastic polymer can change its shape and flexibility, but the polymer chains remain intact. Chemical changes, however, alter the molecular structure of polymers. This can include cross-linking, which creates stronger bonds between polymer chains, or degradation, which breaks down the polymer structure. These chemical changes can dramatically alter the polymer's properties, such as its strength, melting point, or solubility.

33. Why is the process of photosynthesis considered a chemical change?

Photosynthesis is a chemical change because it involves the transformation of reactants (carbon dioxide and water) into new products (glucose and oxygen) through a series of complex chemical reactions. This process, driven by light energy, rearranges atoms and forms new chemical bonds, resulting in substances with different chemical compositions and properties than the original reactants. The fact that the process creates new molecules and cannot be easily reversed further classifies it as a chemical change.

34. How do physical and chemical changes affect the preservation of food?

Food preservation techniques utilize both physical and chemical changes. Physical changes, such as freezing or dehydration, alter the state or moisture content of food without changing its chemical composition, slowing down spoilage. Chemical changes in food preservation often involve adding substances that inhibit microbial growth or enzymatic reactions, like salting or adding preservatives. Some methods, like canning, use both physical (heating) and chemical (pH changes) processes to ensure food safety and longevity.

35. What role do catalysts play in distinguishing between physical and chemical changes?

Catalysts are primarily associated with chemical changes, not physical ones. They speed up chemical reactions by lowering the activation energy required for the reaction to occur, without being consumed in the process. The presence of a catalyst in a process is often an indicator that a chemical change is taking place. In contrast, physical changes do not require catalysts, as they do not involve the breaking or forming of chemical bonds. This distinction helps in identifying whether an observed change is physical or chemical in nature.

36. How do physical and chemical changes differ in their effects on the entropy of a system?

Physical changes typically have a smaller effect on the entropy of a system compared to chemical changes. In physical changes, the arrangement of particles may change, slightly increasing or decreasing entropy. For example, melting ice increases entropy as molecules become more disordered. Chemical changes often involve more significant entropy changes as they alter the number and type of particles in the system. For instance, the decomposition of a complex molecule into simpler ones generally increases entropy more substantially.

37. Why is the process of electrolysis considered a chemical change?

Electrolysis is considered a chemical change because it uses electrical energy to drive non-spontaneous chemical reactions, resulting in the decomposition of compounds into their constituent elements or the formation of new compounds. This process involves the breaking and forming of chemical bonds, changing the chemical composition and properties of the substances involved. For example, the electrolysis of water produces hydrogen and oxygen gases, which have entirely different properties from the original water molecules.

38. How do physical and chemical changes contribute to the carbon cycle?

Both physical and chemical changes play crucial roles in the carbon cycle. Physical changes include the dissolution of carbon dioxide in water and its release from oceans, as well as the physical movement of carbon in various forms through different reservoirs. Chemical changes are equally important, including photosynthesis (which converts CO2 into organic compounds), respiration (which releases CO2), and the formation of carbonate rocks. Understanding both types of changes is essential for comprehending the global carbon cycle and its impact on climate.

39. What is the difference between physical and chemical changes in terms of their effect on chemical equilibrium?

Physical changes generally do not affect chemical equilibrium, as they do not alter the chemical composition or the concentrations of reactants and products in a system. Chemical changes, however, can significantly impact chemical equilibrium. They can shift the balance between reactants and products, potentially driving the reaction in a particular direction according to Le Chatelier's principle. This distinction is crucial in understanding and controlling chemical processes in various applications, from industrial synthesis to biological systems.

40. How do physical and chemical changes differ in their impact on the half-life of radioactive elements?

Physical changes have no effect on the half-life of radioactive elements. The rate of radioactive decay is a nuclear property that remains constant regardless of the physical state or conditions of the element. Chemical changes, which affect the electron configuration of atoms, also do not alter the half-life, as radioactive decay occurs in the nucleus. However, chemical changes can affect how radioactive materials interact with their environment, potentially influencing their distribution or concentration, which is important in fields like nuclear waste management and radioisotope dating.

41. Why is the formation of a precipitate considered a chemical change?

The formation of a precipitate is considered a chemical change because it involves the creation of a new, insoluble substance from soluble reactants through a chemical reaction. This process alters the chemical composition and properties of the original substances. The precipitate has different chemical and physical properties from the reactants, and the process is typically not easily reversible without further chemical reactions. This phenomenon is crucial in various fields, including analytical chemistry and wastewater treatment.

42. How do physical and chemical changes affect the properties of nanomaterials?

In nanomaterials, both physical and chemical changes can have profound effects due to the materials' small size and high surface area-to-volume ratio. Physical changes, such as altering the size or shape of nanoparticles, can significantly affect their optical, electrical, and magnetic properties without changing their chemical composition. Chemical changes in nanomaterials can lead to even more dramatic property alterations, potentially creating materials with entirely new functionalities. Understanding these changes is crucial for designing and optimizing nanomaterials for