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On a daily basis, we are exposed to numerous changes in our environment that we may or may not notice. For example, the melting of wax, rusting of iron, the transformation of bread to a toast, and so on. Chemists have categorized these types of modifications in the same way that they have classed elements and compounds. Physical and chemical changes are the two types of changes that exist in nature. When the physical characteristics of a substance change, it is referred to as a physical change. Furthermore, it makes no internal changes in the object. A chemical change, on the other hand, occurs when a substance's internal structure is altered, resulting in the formation of a new substance. There are several differences between physical and chemical changes that must be grasped in order to comprehend these ideas effectively. In this article, we will learn about the physical and chemical changes, their properties, and the difference between physical and chemical change.
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Keyterms: Environment, substance, compounds, elements, iron, melting of wax, rusting of iron, transformation, molecular composition, material
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What is a physical change?
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Physical change is a process in which a material's physical qualities, such as shape, size, volume, appearance, color, state (i.e. solid, liquid, gas), and so on, change without affecting its molecular composition.
- The chemical characteristics of the object do not change in a physical change.
- These changes are inherently unstable, but they can be reversed with basic physical techniques.
- For instance, when you shred a piece of paper, it just changes shape and size. The properties, however, will remain the same.
- When water transforms into ice or vapor, the chemical properties remain unchanged; only the physical condition changes.
- A change in physical features has no effect on chemical properties in any way.
- Furthermore, the alterations only last a short time.
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The same component or compound exists before or after the alteration, i.e. the object's original physical appearance is preserved. For example, melting of wax, chopping of wood, crumpling of paper, sugar dissolving in water, and so on.
Physical change
What happens in a Physical Change?
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Physical change is a process in which a material's physical qualities, such as shape, size, volume, appearance, color, state (solid, liquid, gas), and so on, change without changing its molecular makeup. These are unstable modifications that can be reversed with basic physical procedures. Physical changes can be seen in the following ways:
- State transitions
- Mixture Separation
- Deformation of the body
- Developing solutions
A physical change occurs when some of the material's features change but the material's uniqueness remains unchanged. When liquid water is heated, it turns into water vapor. The molecules, however, are exactly the same as they were before, notwithstanding the physical changes. Each water molecule still has two hydrogens and one oxygen molecule covalently linked together. As an ice cube melts and gains the capacity to flow, its shape changes. Its arrangement, on the other hand, remains unchanged. Melting is a metaphor for a physical transformation.
Similarly, when you sort a jar of coins and screws into two distinguished piles, you haven't changed the identity of the coins or screws; you've simply separated them into two groups.
Changes can mainly be divided into two categories:
- Reversible Change, and
- Irreversible
Melting is a reversible change since the melted ice cube may be frozen again. All physical changes, including state alterations, are reversible.
- Evaporation (from liquid to gas), icing (from liquid to solid), and condensation are examples of other state transitions (gas to liquid).
- Melting is a reversible physical transformation.
- The salt is said to have entered the aqueous state when it is dissolved in water. By boiling off the water and leaving the salt behind, this can be recovered.
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What is a chemical change?
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A chemical change is defined as the process of rearranging or combining the atoms of one or more substances to generate a new one.
- When a substance undergoes chemical transformation, its chemical character changes and it is transformed into a new substance with a different chemical configuration.
- The polar opposite of physical change is a chemical change.
- It produces a new product as a result of the reaction.
- A chemical change can be detected by the evolution of energy, the formation of bubbles, and temperature variations.
- When you burn a piece of paper or wood, for example, it turns into ash. As a result, the material's composition changes, resulting in the creation of a new product.
- Chemical changes, in other words, affect the properties of a substance during the reaction. This happens as the atoms and molecules of the substances begin to rearrange themselves to generate a new product.
- Furthermore, these alterations are difficult, if not impossible, to reverse; in fact, in most cases, they are irreversible. As a result, it is a permanent modification that affects the melting point, flavor, color, and other properties.
The chemicals involved are referred to as reactants and the end outcome of the reaction is referred to as a product. Because of the development of the new product, the energy change is one of the characteristics of a chemical change. It is impossible to reverse the chemical change once it has occurred. Bleaching a stain, mixing vinegar with baking soda, fermenting grapes, and so on are some examples of chemical change.
Chemical Change
What happens in Chemical Change?
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When bonds between molecules are broken and/or formed, chemical changes occur. This indicates that a substance with one set of attributes (melting point, color, flavor, etc.) is twisted into a substance with a different set of properties. Chemical changes are frequently more difficult to undo than physical alterations.
- The burning of a candle is an example of a chemical change. The process of burning a candle does, in fact, result in the formation of various chemicals (namely, carbon dioxide and water).
- Another example of a chemical change is the combustion of natural gas in the furnace. Not only does the appearance change in this situation, but the atom's structure also changes. The chemical characteristics of the new substance differ from those of the old. As a result, there has been a chemical change.
Some signs of chemical change include energy alterations that occur during chemical changes, but others include the production of new substances with unique properties during a chemical change.
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Factors affecting Physical and Chemical Change
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It is critical to comprehend the factors that influence the chemical and physical transformations of matter. It’s all about energy and states of matter when it comes to physical changes. They are observable and quantifiable. Forces such as motion, temperature, and pressure generate physical changes. But on a far smaller scale, chemical changes take place. The majority of these molecule-to-molecule variations go unnoticed.
Temperature, concentration, surface area, inhibitors, and catalysts are all factors that influence the rate of chemical change. The following are some instances of how these factors influence chemical and physical changes.
- The chemical alteration of the matter is influenced by temperature. When the temperature rises, the reaction rate rises, and vice versa. If the temperature drops or rises, fewer or more particles will have activation energy.
- Second, the chemical alteration of the matter is influenced by concentration. When the concentration of a substance is increased, the number of particles per unit of volume increases, and vice versa. As a result, particles clash more frequently, increasing the rate of reaction. When there is a higher concentration of particles, there is a larger likelihood that they will collide.
- The chemical alteration of the matter is also influenced by surface area. When you reduce the surface area, you slow down your reaction time. The inverse is also true. A finely divided powder reacts faster than a huge clump of the same substance.
- An inhibitor is another factor that influences matter's chemical transformation. When a specific material is added to a chemical reaction, it slows it down. It's a kind of effector that slows or stops a chemical reaction. Negative catalysts are a term used to describe these materials.
- Another factor that affects the chemical transformation of matter is a catalyst. When catalysts are added to a chemical reaction, it accelerates it. A catalyst alters the energy pathway for a chemical reaction by providing a channel that decreases the activation energy, allowing more particles to collide successfully.
- Finally, solubility has an impact on matter's physical transformation. When something is highly soluble, it takes on a different physical appearance more quickly. In water, salt is extremely soluble.
Each of these variables has an impact on the chemical or physical changes that occur in matter. It is critical to be able to distinguish between the two types of changes and to understand how these variables influence the rate of change in matter.
Chemical and physical change
Difference between Physical Change and Chemical Change
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| Physical Change | Chemical Change |
|---|---|
| Physical change is a process in which the physical properties of a substance, such as a shape, size, volume, appearance, color, state (solid, liquid, gas), and so on, changes without affecting its molecular structure. | The process of rearranging or mixing the atoms of one or more substances to create a new one is known as chemical change. |
| The makeup of a substance does not change despite the fact that its molecules are rearranged when it undergoes a physical change. | A substance's molecular composition is completely altered when it experiences a chemical change. As a result, chemical change results in the production of new substances. |
| Physical change is reversible, which means that the original substance can be restored. | Chemical changes are irreversible, which means that the original substance cannot be restored. |
| Physical changes, in general, do not necessitate the formation of energy. | The formation of energy is frequently involved in chemical changes (which can be in the form of heat, light, sound, etc.) |
| Energy absorption is little to non-existent in physical change. | Absorption and evolution of energy occur in chemical changes. |
| Only physical properties, such as shape and size, are affected by physical change. | Chemical changes disrupt the substance's physical and chemical properties, as well as its composition. |
| Physical change is only a short-term phenomenon. A physical change does not result in the formation of new material. | A chemical change is a long-term transformation. One or more new substances are always formed when a chemical change occurs. |
| Physical changes include the freezing of water, the melting of wax, the boiling of water, and so on. | Some examples of chemical change are food digestion, coal combustion, corrosion, and so on. |
Physical vs Chemical Change
Things to Remember
- A physical change occurs when molecules reorganize themselves but the interior composition remains unchanged. Physical changes include cutting wood, freezing water, melting ice cubes, and smashing a tomato, etc.
- The process by which atoms from one or more substances rearrange or combine to form a new material is known as chemical transformation. Examples include wood burning, food digestion, cake baking, and iron rusting.
- When it comes to physical transformations, it's all about energy and states of matter. Chemical changes, on the other hand, occur on a far smaller scale.
- The substance's physical attributes, such as shape, size, and volume, will change as a result of physical change. All of this occurs without a change in molecular composition, whereas odor, temperature, and the creation of bubbles are indications of chemical change.
- The main distinction between physical and chemical changes is that physical changes can typically be reversed, whereas chemical changes can not be.
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Sample Questions
Ques. Distinguish between physical and chemical changes? (5 marks)
Ans. It's critical to recognize the distinctions between physical and chemical changes.
- Physical changes do not modify the make-up of the substance, whereas chemical changes alter the chemical and molecular properties.
- No new substance is formed in a physical change whereas chemical changes are those that result in the creation of a new substance.
- Energy is involved in physical changes. The substance is altered by the energy, but the substance's composition or make-up remains unchanged. When you tread on a Coke can, for example, you expend energy to modify the form of the can, yet the can is still made of the same aluminium as before.
Chemical changes, like physical changes, take energy, but the end result is a new material that is chemically unique from the original.
- In a chemical reaction, the structure of the molecules changes. Chemical bonds are broken, resulting in new molecular configurations.
Ques. What distinguishes a physical change from a chemical change? (3 marks)
Ans. While undergoing a physical change, a material may change shapes or forms, but no chemical processes or new compounds are generated. A chemical change occurs when matter undergoes a chemical reaction, whereas a physical change occurs when matter undergoes a physical transformation but does not lose its chemical identity.
Ques. Is it possible to reverse physical changes? (3 marks)
Ans. All physical changes that result in a state transition are reversible. Vapourization (from liquid to gas), freezing (from liquid to solid), and condensation are examples of other state transitions (gas to liquid). Dissolving is a reversible physical transformation.
Ques. What factors influences chemical change? (4 marks)
Ans. A chemical change can be influenced by four basic factors:
- The concentration of reactants- Increasing the concentration of one or more reactants will usually speed up the reaction.
- Surface area and physical state of the reactants.
- The presence of a catalyst is required.
- Temperature.
Ques. What characteristics do physical changes have? (2 marks)
Ans. A change in physical properties is referred to as a physical change. Physical qualities in physical change include melting, transitioning to a gas, changes in strength, durability, crystal form, textural changes, shape, size, color, volume, and density.
Ques. What is conserved when it comes to physical changes? (2 marks)
Ans. Physical and chemical changes can modify the form of matter, but all of these changes conserve matter. Before and after the transition, the same amount of matter exists- nothing is generated or destroyed. The Law of Conservation of Mass is the name given to this notion.
Ques. How does energy change as a result of physical and chemical change? (3 marks)
Ans. When physical or chemical changes take place, they are usually accompanied by an energy transfer. Energy is neither created nor destroyed in any physical or chemical process, according to the law of conservation of energy. To put it in another way, all of the universe’s energy is conserved.
Ques. How can a chemical change be detected? (4 marks)
Ans. A chemical change can be detected in five ways:
- Change in color.
- Odor formation.
- Variation in temperature.
- Evolution of gas or bubble formation.
- Formation of condensate or precipitate.
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