Our planet is made of different elements, which pass through physical and chemical changes from time to time; this includes us, humans.
Every day, so many changes occur in the cause of our living.
Activities such as the blending of fruits, the sourness of milk, the lilting of a match stick, the melting of wax, and so on all pass through a type of change to occur.
During these activities, physical and chemical changes take place.
Did you know the human body undergoes chemical changes whenever our food is transformed into energy? Well, that’s not the only type of change that happens to us.
Whenever your body mass increases, you have passed through physical change. But with so many changes happening around us, how can one tell which is a physical or chemical change?
Despite formal instruction, many people have difficulties distinguishing between physical and chemical changes, and the difference is sometimes arbitrary.
This confusion includes the assumption that new substances are created after a physical change.
As a result, one may easily confuse mere physical occurrences such as melting, evaporation, and boiling, to be chemical changes, due to the reactions that take place.
What is Physical Change
A physical change occurs when the physical qualities of a substance, such as its form, size, volume, appearance, color, state, etc, change without affecting its molecular composition.
In a physical change, the elements or compounds in the composition of the matter are preserved after alteration.
However, these changes are reversible with basic physical techniques and are inherently unstable.
Some common examples of physical changes include wax melting, water boiling, woodcutting, sugar dissolving in water, paper crumpling, and so on.
Characteristics of Physical Changes
- The composition of the substance remains the same
- No new substance is formed.
- The change is physical and is reversible.
- Physical Changes can be used in separating mixtures
Physical changes may result in a change in appearance without changing the initial composition of the substance. Some common changes include: changes in texture, color, temperature, shape.
Factors responsible for Physical Change
The factors responsible for physical changes in any matter include:
- Change of state: boiling point and melting point
- Physical properties of the composition: luster, solubility, mass, malleability, viscosity, volume, ability to be drawn into a thin wire density, etc.
What is Chemical Change
Chemical changes can also be called chemical reaction. This takes place when the bonds between molecules are broken and/or formed.
A chemical reaction can be between two or more compositions known as reactants. Under certain conditions, these reactants interact with each other and the outcome is called a product.
Chemical changes are often more difficult to reverse than physical ones.
Some examples of chemical changes include; rotting, burning, frying, and rusting, as they result in the formation of totally new chemical compounds. Burned wood, for instance, produces ash, carbon dioxide, and water.
Also, when iron is exposed to water, it transforms into a combination of hydrated iron oxides and hydroxides.
Characteristics of Chemical Change
- Only the chemical characteristics of a substance will change.
- Chemical alterations cannot be reversed by basic physical techniques.
- Not all chemical changes are irreversible, although some are.
- A new substance will be created here.
Factors Affecting Chemical Change
- The concentration of reactants. The pace of reaction is frequently increased by increasing the concentration of one or more reactants.
- Surface area and physical condition of the reactants
- The temperature…
- There is a catalyst present.
How to tell if a chemical reaction has occurred
Even while atoms breaking and establishing bonds is what characterizes chemical changes, we can’t see it.
Other observations must be made to establish that a chemical change has happened.
Some signs of chemical change include the energy shifts that occur during chemical reactions, but others include the fact that new compounds with different characteristics are formed because of the chemical change:
- Increase or decrease in temperature
- Light is emitted.
- Different odors or tastes.
- There is an unexpected colour change may occur, usually contrary to a regular mixture.
- Presences of a precipitate.
- Bubbles or gasses are produced under regular conditions (when the mixture is not boiling).
Difference between Physical and Chemical Change
To help you better understand the differences between physical and chemical changes, the table below summarizes all that has been written in this article.
|Physical Change||Chemical Change|
|The molecules are rearranged during a physical change, but their true makeup stays unchanged.||A chemical change causes a substance’s atom configuration to change, resulting in the formation of a new compound.|
|Only physical attributes, such as shape and size, are affected by physical change.||Chemical changes disrupt the substance’s physical and chemical characteristics, as well as its makeup.|
|Energy absorption is little to non-existent in physical transformation.||Absorption and emission of energy occur in chemical reactions.|
|There is no new material created during physical change.||A chemical shift is always accompanied by the appearance of one or more new substances (s).|
|Physical alteration is reversible, which means that the original material may be restored.||Chemical transformations are irreversible, meaning that the original substance cannot be restored.|
|Physical changes are temporary.||A chemical change is a long-term transformation.|
|Examples include Freezing water, melting wax, boiling water, etc.||Examples include Food digestion, coal combustion, corrosion, etc.|
In summary, one may easily differentiate a physical change from a chemical change through the final composition of the substance after a reaction.
A chemical study, such as mass spectroscopy, on the substance, is a great approach to establish its composition before and after a reaction, to be fully confident whether a change is physical or chemical.
However, if you can’t conduct such chemical analysis, you can as well use direct observation.
For example; variation in the appearance, smell, or plain display of a sample of matter gives off a physical reaction.
While Increase or decrease in temperature, emission of light, change in smell or tastes, and an unexpected and contrary change in color, gives away chemical changes.