What do you mean by physical change and chemical change? And give the examples of each

Question

Answer

the change which can be undone is called physical change and the change which can be undone is called chemical change

Answer

Physical change is a temporary change. Physical properties of a substance. No new substance is  formed. Ex of physical change- tearing of paper. Chemical change is a permanent change. Chemical properties of a substance changes. New substance is formed. Ex of chemical change- burning of paper.

Answer

Physical Change:
A physical change refers to a change in the physical properties of a substance without altering its chemical composition. In other words, the molecular structure remains the same, but there are noticeable changes in the appearance, shape, size, or state of the substance.

Examples of Physical Changes:
1. Melting Ice: When solid ice is heated, it absorbs energy and undergoes a physical change, transforming into liquid water. The molecular structure of H2O remains the same, but the arrangement and spacing of the molecules change.

2. Boiling Water: As water is heated, it reaches its boiling point and changes from a liquid to a vapor state, forming steam. The chemical composition of water (H2O) remains unchanged, but its physical state changes.

3. Dissolving Salt: When salt (NaCl) is dissolved in water, it separates into individual ions (Na+ and Cl-) that disperse throughout the liquid. This is a physical change as the chemical composition of the salt remains intact, but its physical state changes from a solid to a solution.

4. Cutting Paper: When a piece of paper is cut into smaller pieces, its physical appearance changes, but the paper remains composed of cellulose fibers. The cutting process only alters the size and shape of the paper, not its chemical composition.

Chemical Change:
A chemical change, also known as a chemical reaction, occurs when substances combine or break apart to form new substances with different chemical properties. During a chemical change, the molecular structure and composition of the substances involved are altered.

Examples of Chemical Changes:
1. Rusting of Iron: When iron is exposed to oxygen and moisture for a prolonged period, it undergoes a chemical change known as rusting. The iron reacts with oxygen to form iron oxide (rust), resulting in a change in color, texture, and chemical composition.

2. Burning Wood: Combustion of wood is a chemical change where the cellulose and lignin in wood react with oxygen in the presence of heat, producing carbon dioxide, water vapor, and ash. The original composition of wood changes, and energy is released in the form of heat and light.

3. Digestion of Food: When food is consumed and digested, enzymes in the body break down complex molecules into simpler ones through chemical reactions. This process involves the conversion of carbohydrates, proteins, and fats into smaller molecules that can be absorbed and utilized by the body.

4. Photosynthesis: In plants, the process of photosynthesis involves a series of chemical changes. Chlorophyll captures sunlight, which is then used to convert carbon dioxide and water into glucose and oxygen. This chemical reaction is vital for the plant's growth and energy production.

In summary, physical changes involve alterations in the physical properties of a substance without changing its chemical composition, while chemical changes involve the formation of new substances with different chemical properties.

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