Difference Between Physical and Chemical Change for JEE Main 2024

Change is occurring all around us all of the time. Just as chemists have categorized elements and compounds, they have also classified kinds of changes. Changes can be classified as physical or chemical changes.

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In our everyday life, we come across many changes in our surroundings, for example, souring of milk, rusting of iron, bread becoming toast, stretching of a rubber band, melting of wax, lilting of a match stick, etc. All these changes that take place nearby are chemical changes or physical changes. Physical changes are the changes that change the physical characters of the material, without making any change in their interior structure.

On the other hand, a chemical change is one that changes the internal structure of the substance, so as to proceed with a new substance.

Definition of Physical Change

Physical change is a process in which the material experiences alteration in its physical properties like shape, size, volume, appearance, color, state (i.e. solid, liquid, gas), etc., that, without making any alteration in their molecular composition. These alterations are unstable; that can be reversed using simple physical methods.

The same element or compound occurs prior, or after the change, i.e. the original physical appearance of the object remains unchanged. For instance, melting of wax, dissolving sugar in water, boiling of water, chopping wood, crumpling of paper, etc.

Definition of Chemical Change

Chemical Change is defined as the procedure in which the atoms of one or more substances are reordered or combined to form a new substance. When a substance experiences a chemical change, the chemical character of the substance changes and it is converted into a different substance with a different chemical configuration. The evolution of energy, the creation of bubbles, and changes in temperature are some signs of chemical change.

Alternately, known as a chemical reaction, where the substances involved are called reactants, and the result of the reaction is known as a product. Energy change is one of the features of a chemical change, because of the development of the new product. Once the chemical alteration takes place, it cannot be overturned. For instance, bleaching a stain, adding vinegar to baking soda, fermenting grapes, etc.

Chemical Change vs. Physical Change

The primary difference between a chemical change and a physical change is what happens to a substance’s composition. The basic definitions of chemical and physical changes are given below:

• Chemical Change: It is a process in which chemical bonds are broken or created to make a new substance.

• Physical Change: It is a process in which a substance changes its state of matter, but chemical bonds stay intact.

When the matter goes through a chemical change, it can’t return to its original state without additional reactions whereas when it goes through a physical change, it only needs to return to its original state of matter. The molecules of the substance haven't changed at all. There are really only two criteria for whether a change is chemical or physical, after the change does it look the same and can

you change it back? 

If the answer is yes, the change is physical every time. If the answer is no, the change is chemical every time.

Physical Change

Physical change is a process in which the material experiences change in its physical properties like shape, size, volume, appearance, color, state (i.e. solid, liquid, gas), etc., that, without making any changes in its molecular composition. These changes are unstable and can be overturned using simple physical methods. Some kinds of physical changes include

• Changes of state

• Separation of a mixture

• Physical deformation

• Making solutions

As an ice cube liquefies, its shape is altered as it obtains the ability to flow. However, its arrangement does not change. Melting is an illustration of a physical change. A physical change is a change to a sample of matter in which some character of the material changes, but the uniqueness of the matter does not. When we boil the liquid water, it transforms into water vapor. But even though the physical character has changed, the molecules are precisely the same as they were before. We still have each water molecule comprising two hydrogen molecules and one oxygen molecule covalently bonded. When you have a jar holding a group of pennies and nickels and you sort the mixture so that you have one heap of pennies and another pile of nickels, you have not transformed the identity of either the pennies or the nickels - you've simply separated them into two groups. This would be an instance of a physical change. Physical changes can more be classified as reversible or irreversible. The melted ice cube may be frozen again, so melting is a reversible change. Physical changes that include a change of state are all reversible. Other changes of the state include evaporation (liquid to gas), icing (liquid to solid), and condensation (gas to liquid). Melting is also a reversible physical change. When salt is dissolved into water, the salt is said to have gone into the aqueous state. This can be recovered by boiling off the water, leaving the salt behind.

Characteristics of Physical Changes

• The physical characteristics of a substance will change nothing more than that.

• no different substance is formed.

• The physical changes are reversible in nature as we know.

• Separating Mixtures through Physical Changes

Solution mixtures can be separated into their basic substances by physical methods that depend upon differences in some physical properties, such as changes in their boiling points. Two of these separation approaches are distillation and crystallization. Distillation makes use of variation in volatility, to measure how easily a substance is transformed into a gas at a given temperature. A simple distillation apparatus for splitting a mixture of substances, at least one of which is a liquid. The highly volatile component boils first and is condensed back to its natural states in the water-cooled condenser, from which it flows into the receiving flask. If a mixture of salt and water is distilled, for example, the highly volatile component, clean water, collects in the receiving flask, while the salt remains in the distillation flask.

A solution of two or more liquids with dissimilar boiling points can be separated with a more complex distillation apparatus.

One sample is the filtering of crude petroleum into a variety of useful products: aviation fuel, gasoline, diesel fuel, kerosene, and lubricating oil (in the approximate order of decreasing volatility). Another illustration is the purification of alcoholic spirits such as whiskey or brandy.

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Another instance of using physical properties to separate solutions is filtration. Separation operations isolate fluids from solids by adding a medium through which only the fluid (liquid) can pass. The fluid that passes through is termed the filtrate. There are several different methods of filtration; all-purpose is to attain the separation of substances. Separation is attained by some form of interface between the substance or objects to be removed and the filter. The mixture that is to pass through the filter must be a liquid, i.e. a liquid or gas. Techniques of filtration vary depending on the location of the targeted material, i.e. whether it is melted in the fluid phase or suspended as a solid.

Chemical Change

Chemical changes happen when bonds are broken and/or made between molecules. This means that one material with a specific set of properties (such as MP, color, taste, etc) is twisted into a different substance with different properties. Chemical changes are regularly harder to reverse than physical changes.

One illustration of a chemical change is the burning of candles. The action of a burning candle truly results in the formation of different chemicals (carbon dioxide and water, to be exact) from the burning of the wax. Another instance of a chemical change is when natural gas is burned in your furnace. On the left, we have a particle of methane, CH₄ and two molecules of oxygen, O₂ while on the right we have two atoms of water, H₂O and one atom of carbon dioxide, CO₂. In this case, not only has the look changed but also the structure of the atom has changed. The new compound does not have the same chemical properties as the original ones have. So, this is a chemical change.

We can't see atoms breaking and forming bonds, even though that's what defines chemical changes. We have to create other observations to show that a chemical change has occurred. Some of the indications for chemical change will include the energy changes that happen in chemical changes, but some sign involves the fact that new substances with different properties are produced in a chemical change.

Remarks that Help to Sign Chemical Change Include:

• Temperature changes (increases or decreases).

• Unexpected color shift (a material with an altered color is prepared, rather than just mixing the original colors together).

• Light is given off.

• Different smell or taste (do not try to taste your chemistry experiments, though!).

• A solid method if two clear liquids are mixed (look for floaties - technically known as a precipitate).

• Bubbles are made (but the mixture is not boiling - you prepare a substance that is a gas at the temperature of the beginning materials, instead of a liquid). 

Characteristics of Chemical Changes

• For a material, only the chemical properties will alter.

• Here new substances will be produced.

• Not all but certain of the chemical changes are irreversible.

• By simple physical means, chemical changes cannot be overturned.

Difference Between Physical and Chemical Change

A change in which the atoms are reorganized, but their composition on the inside remains the same is called Physical Change. A procedure in which the substance converts into a new substance, having a dissimilar chemical composition, is called Chemical Change.

1. Some mutual examples of physical changes are vaporization, condensation, FP/MP/BP of water. On the other hand, the illustrations of chemical change are metabolism, combustion, cooking of eggs, etc.

2. Physical change is short-term; they are easily reversible. As compared to this, the chemical change is long-lasting, i.e. they cannot be overturned, even by reversing conditions.

3. In the physical change, only the form of the substance is altered, but no new product is produced. On the other hand, when there is a chemical reaction, a totally different product is produced, whose properties are totally different from that of the reacting substances.

4. In a physical change, the original substance can be recovered, by basic physical methods. As compared, in chemical change the original substance no longer exists, and so it cannot be recovered back.

5. In the physical change, alteration in the physical characteristics of the substance is seen, such as size, shape, texture, smell, appearance, density and so on. On the other hand, chemical change includes the alteration in the chemical properties of the substance, i.e. change in its chemical nature.

6. In the physical change, not or very little volume of energy is absorbed or liberated as light or sound energy, heat. Contrasting chemical change, wherein huge energy is absorbed or liberated as heat, light or sound energy.

Chemical and Physical Change Examples

• A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity.

• Examples of chemical changes are burning, cooking, rusting, and rotting.

• Examples of physical changes are boiling, melting, freezing, and shredding.

• Many physical changes are reversible if sufficient energy is supplied. The only way to reverse a chemical change is via another chemical reaction.

Conclusion

A substance can undergo physical and chemical changes. These changes can cause a substance to change its form or to change into a completely different substance. The main difference between physical and chemical change is that a physical change does not change the chemical composition of a substance whereas a chemical change changes the chemical composition of substances. 

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.