Chemical and Physical changes - 88tuition

Chemical and Physical changes - 88tuition



Change refers to any deviation from an object's initial condition. The transformation of water into ice, of paper into ashes, and of metals into tools are all instances of transformations. In some cases, the alterations may be undone, while in others, they may not. When anything changes, either physically or chemically, it may be undone. During a chemical transformation, new compounds are created, but during a physical transformation, simply a shift in state or size takes place. 

Definition of Physical Change

Alterations in a substance's physical state or form occur independently of the chemical elements that make it up. Separation of constituents from a mixture can also be achieved by means of physical changes. Big physical shifts can be undone. Physical changes include the boiling of water, breaking of glass, cutting of wood, and melting of ice. With a physical transformation, the structure of the materials remains the same even after the transformation has taken place. 

Characteristics of Physical Changes

During a physical transformation, the substance's shape, size, volume, mass, etc. will alter, but its chemical characteristics will remain unchanged. No novel chemicals are being created by these transformations. The change might be temporary or permanent. In addition, it does not absorb or develop any energy. Temporary alterations to the body are possible. Scratching a block of wood with your finger creates a rough texture, but rubbing it with sandpaper makes the surface smooth and eliminates the roughness. Just changing the wood's surface texture does not make it a new substance. Pieces of metal may be heated in a flame until they glow, yet metal retains its properties whether hot or cold. In the same way, when a substance changes phase, there are no chemical or biological transformations taking place. The substance's composition does not alter over time; it remains constant. Ice melting into water causes the water to boil, producing steam. Water's molecular structure is the same whether it's in solid, liquid, or gaseous form.

Examples of Physical Change

Some common examples are

  1. Rusting of iron 

  2. Freezing water 

  3. Grinding spices 

  4. Shredding paper 

  5. Bending a wire

Definition of Chemical Change

A change in the constitution of a substance results in a chemical transformation. In this process, chemical bonds are broken and new ones are formed. Hence, a molecule cannot be returned to its previous shape or size. It is challenging to detect a chemical shift. Changes in temperature, colour, odour production, and precipitation formation are therefore indicators of chemical changes. Energy is necessary to break chemical bonds inside a substance, hence energy is both absorbed and released when bonds are produced. The chemical cold pack included in first aid kits is an example of a chemical reaction that absorbs and emits heat energy.

Characteristics of Chemical Changes

Changes in colour, creation of gas, emission of odour, and precipitation are observable characteristics of chemical reactions. As iron combines with oxygen, it changes colour from red to brown due to chemical processes. On the other hand, spoiled food may have an odour that indicates a chemical shift. If food is left unattended for extended periods of time or has beyond its expiration date, it will ultimately degrade and often emit a foul odour. This is due to a chemical reaction that happens when food begins to disintegrate and decay, resulting in the production of new compounds with a distinct odour.

Precipitate formation is a frequent indicator of a chemical reaction. This occurs when the dissolved chemicals in the solution create a solid material. Consider, for instance, the combination of vinegar and baking soda. When these two substances are combined, foaming occurs. Carbon dioxide is formed by their chemical reaction. In comparison to physical processes, chemical reactions cannot be reversed easily.

Examples of Chemical change

Some common chemical changes are:

  1. Burning of wood 

  2. Rusting of iron

  3. Digestion of food 

  4. Fermentation of alcohol 

  5. Combustion of gasoline

Title: Chemical and Physical change

Difference Between Physical and Chemical Changes

Physical Changes

Chemical Changes

Physical change often entails modifications to physical characteristics like size and shape and excludes the emission of energy such as light, sound, or heat.

Energy can be created by a chemical reaction in the form of light, heat, sound, etc

Usually, reversible

Usually, irreversible

No effect on the chemical bonds

Affects the chemical bonds

Changes occur when heating, and cooling occurs

Accompanied by absorption or release of energy

No formation of new substances

The formation of new substances takes place

The material's composition stays the same. H2O is the chemical formula for water in its liquid, gaseous, and ice-forming states

The substance's molecular structure is altered during a chemical reaction. For instance, magnesium ribbon burns to produce magnesium oxide.


A substance's qualities, including its state of matter, structure, and chemical characteristics like a chemical formula, can differ wildly. Physical and chemical changes can be classified into many categories. The difference between a physical change and a chemical change is considered in the qualities, whether they are chemical or physical. Like how ice cream melts, only the state of matter changes from solid to liquid; the texture and other characteristics stay the same. In the chemical process of photosynthesis, sugars are produced from sunlight, carbon dioxide, and water.

Frequently Asked Questions

1. What is an irreversible change?

As the name suggests,  an irreversible change can not be undone. It results in the change in the chemical nature of the atom itself. All chemical changes are irreversible and they can not be undone through simple physical means. 

2. What effect does temperature have on physical and chemical changes?

A temperature change affects both physical and chemical reaction. A chemical reaction requires a proper temperature to occur as it results in the making and breaking of bonds which results in an exchange of energy. A physical change also depends on temperature as with the change in temperature the state of matter changes. 

3. What is bond dissociation?

Bond dissociation is the breaking of bonds between two atoms in a molecule or a compound.  Bond dissociation always requires some amount of energy depending on the strength of the bond.