The basic difference between physical and chemical change is that physical change alters the form or state of a substance without creating new substances, while a chemical change results in the formation of new substances with different properties.
Physical vs Chemical Change
The key difference between physical and chemical change is given below:
| Aspect | Physical Change | Chemical Change |
| Nature of Change | Alters the physical properties without forming new substances. | Results in the formation of new substances with different properties. |
| Particle Arrangement | Rearranges or changes the arrangement of particles without altering their fundamental identity. | Involves a rearrangement of atoms and molecules, leading to the creation of new chemical substances. |
| Reversibility | Often reversible, meaning the original substance can be restored by reversing the change. | Generally irreversible, as the original substances cannot be easily obtained from the new products. |
| Energy Change | May involve the exchange of energy, such as heat, but the energy change does not necessarily indicate a chemical reaction. | Involves a significant exchange of energy, often resulting in the release or absorption of heat, light, or other forms of energy. |
| Formation of New Substances | No new substances are formed; only the physical state or appearance changes. | New substances with different chemical properties are formed. |
| Examples | Melting ice, boiling water, tearing paper, dissolving salt in water. | Burning wood, rusting iron, digestion of food, baking a cake. |
| Observables | Change in state (solid to liquid, etc.), change in shape or size, change in density. | Color change, gas production (bubbles), formation of precipitate, odor change. |
What is Physical Change?
A physical change refers to a type of change in matter where the substance’s chemical composition remains the same, but its physical properties alter. In simpler terms, the arrangement, shape, size, or state of the matter can change, but the fundamental nature of the substance remains unchanged.
Examples
Changes in state of matter
When a substance changes from one state (solid, liquid, gas) to another through processes like melting, freezing, vaporization, condensation, or sublimation.
Changes in size or shape
Cutting, tearing, crushing, or reshaping a material, like cutting a piece of paper or breaking a glass.
Dissolving
When a solid substance dissolves in a liquid, like sugar dissolving in water.
Mixing
Combining different substances without altering their chemical compositions, such as mixing salt and pepper.
Change in color
While some color changes might be indicative of a chemical reaction, certain cases involve only a change in the way light interacts with the substance, not its actual composition.
What is chemical change?
A chemical change, also known as a chemical reaction, refers to a process in which one or more substances undergo a transformation, resulting in the formation of new substances with different chemical properties. During a chemical change, the molecular structure of the involved substances is altered, leading to the creation of entirely new arrangements of atoms.
Indicators
Formation of New Substances
New substances are produced as a result of the reaction. These substances often have different physical and chemical properties compared to the initial substances.
Energy Change
Chemical reactions typically involve the exchange or transformation of energy. This can manifest as heat, light, or other forms of energy being released or absorbed during the reaction.
Color Change
The color of the substances involved may change as a result of the reaction.
Formation of Precipitate
In some reactions, a solid substance called a precipitate may form when two solutions are mixed. This indicates the formation of a new substance.
Gas Production
Gases might be released during a chemical reaction, leading to the formation of bubbles or a change in pressure.
Irreversibility
Chemical changes are often irreversible, meaning it’s challenging or impossible to revert the substances back to their original forms.