Chemical Changes occur when a new bond between molecules is either formed or broken. This change results in new and different kinds of properties than the parent molecule.
When a chemical change occurs, there is rearrangement of atoms which changes the chemical composition of the substance as a whole, due to which this process is generally irreversible. When multiple compounds react with one another, two types of changes can be observed, one is the chemical change, and another is the physical change.
How chemical change occurs is a question asked frequently.
In physical change, no bonds are broken or formed. Thus, physical change can be observed when there is a change in state of the material, i.e., solid, liquid or gaseous form, physical deformation, etc.
Chemical change is when the internal composition of the matter changes, which results in change in color, change in odor, change in melting and boiling points, formation of precipitate, formation of bubbles, release of gases, change in composition etc. One of the significant points is, if the reaction is difficult to reverse or impossible to reverse.
Energy is always required to put forward a chemical reaction. Sometimes, the energy is absorbed by the molecules to carry forward the reaction and sometimes, energy is released.
Factors like temperature, presence of catalysts, concentration of the reactants, presence of moisture (for some reactions), state of reactants (solid, liquid, gas, and ions), etc., affect the reaction rate.
In this section, we will learn about how chemical change occurs, factors affecting chemical change, requirements for a chemical change to occur, types of chemical change, etc.
1. How Chemical Change Occurs?
When chemical change occurs, a substance is transformed into a different substance.
Chemical change occurs when the bond between two or more reactants is created, broken or simply rearranged.
Energy is required for both breaking and creating a bond. Sometimes, the energy needed to break the bond is higher than the energy required in making a bond. This binding or splitting changes numerous properties of the substance such as odor, color, state, melting point, boiling point, taste, etc.
For E.g.:- Rusting of iron is an example of chemical change as the iron reacts with oxygen and water and a different substance is formed, which is rust while boiling of water is not a chemical change as the water molecules only change their state (i.e., from liquid to gaseous) but not its form.
Chemical change is usually irreversible but in some cases, it is reversible too!
Similarly, physical changes are reversible but in some cases, irreversible too.
For E.g.:- Tearing off a paper is a physical act or change but it cannot be reversed. Even if we try to join the paper with different means, it won’t come back to its original form.
2. Why are chemical reactions important?
Chemical Change assists us in understanding the properties of matter.
Chemical changes help us understand the processes happening all around the world as well as in the universe.
Every action that occurs in the universe is a result of chemical change. Once the properties of matter are understood, one can also understand how to control a reaction. All this information helps in recognizing the ongoing processes and in developing or inventing new things.
Read more on Chemical Change Examples
3. Which is the most crucial chemical change?
The basic necessity for all life forms to survive in the biosphere is oxygen and food.
Photosynthesis was chosen as the most crucial chemical change in 1988.
Though humans, animals or other organisms do not perform photosynthesis on their own, they highly depend on plants (who carry out photosynthesis) for food and oxygen.
4. What are some examples of chemical change observed in everyday life?
One of the best and the most straightforward examples of chemical change that we observe in our day-to-day life is cooking.
Various physical and chemical changes take place when food is cooked. Another easy example is combustion.
Nowadays, the electric gas stove has taken over, but a large part of the world still uses the conventional gas stove that utilizes fire. Fire is nothing but a type of chemical reaction.
5. Are all chemical changes Irreversible?
Not all chemical changes are irreversible.
Yes, you read it right; some chemical changes are reversible like, the Haber process.
In Haber process, hydrogen and nitrogen combine to form ammonia, which can later be separated into hydrogen and nitrogen again.
But this happens only till equilibrium is reached. Once the equilibrium is reached, the reaction cannot be carried forward or backwards.
6. Is mass conserved in a chemical reaction?
No, the mass is not conserved in a chemical reaction.
Yet, sometimes it is, but most of the time, it is converted into energy.
According to the famous equation given by Einstein, which states that mass can be converted into energy and energy can be converted into mass. The equation is given as:
E = mc2
Where, E = Energy; m = mass; c = speed of light in vacuum
More often than not, the mass converted into energy is in a negligible amount in atomic reactions. In nuclear reactions, the energy absorbed or released is relatively high, and thus, the change in mass is significantly visible.
7. What are the different types of chemical changes?
The different types of chemical changes are:
- Organic Chemical Changes
- Inorganic Chemical Changes
- Biochemical changes
The organic type of chemical change deals with the chemistry of carbon, and the inorganic type of change deals with the chemistry of all the other elements and their compounds other than carbon. In contrast biochemical change involves the chemistry of the living organisms controlled by proteins and enzymes.