Understanding Chemical vs. Physical Processes

The question asks us to identify the process from the given options that does NOT involve a chemical reaction. To answer this, we need to understand the difference between a chemical change (which involves a chemical reaction) and a physical change.

• Chemical Change: A change where new substances are formed. The chemical composition of the substance changes. Examples include burning, rusting, cooking, ripening.
• Physical Change: A change where the form or appearance of a substance changes, but its chemical composition remains the same. Examples include melting, freezing, boiling, cutting, dissolving, evaporation.

Analyzing the Given Processes

Let's look at each option to determine if it involves a chemical reaction or is purely a physical process.

1. Cloth Cleaning using Detergent

Cleaning cloth with detergent involves more than just physical action. Detergents are chemicals (surfactants) that reduce the surface tension of water and interact chemically with grease and dirt particles. They help lift and emulsify oil and dirt, allowing them to be washed away. While physical agitation is involved, the action of the detergent relies on chemical properties and interactions with the dirt and water. This involves chemical processes, even if it's not a simple reaction like combustion.

2. Ripening of Mango

Ripening is a complex biological process that involves many chemical reactions occurring within the fruit. Enzymes catalyze the breakdown of starch into sugars (making the fruit sweet), the production of volatile organic compounds (creating the aroma), changes in pigments (causing colour change), and softening of tissues. These are all chemical transformations.

3. Change of Colour of Turmeric due to Soap

Turmeric contains a natural pigment called curcumin, which acts as an acid-base indicator. Soap solutions are typically alkaline (basic). When turmeric comes into contact with a basic substance like soap, a chemical reaction occurs between curcumin and the alkali. This reaction causes the curcumin molecule to change its structure slightly, which alters the way it absorbs and reflects light, resulting in a colour change from yellow to reddish-brown. This is a clear example of a chemical reaction.

4. Cooling Effect of Nail Polish Remover

Nail polish remover, commonly containing acetone or ethyl acetate, produces a cooling sensation when applied to the skin because it evaporates very quickly. Evaporation is the process where a liquid turns into a gas. This process requires energy (heat), which is absorbed from the surroundings (like your skin). As the liquid evaporates, it takes heat away, causing a cooling effect. The chemical composition of the nail polish remover itself does not change; it just changes its state from liquid to gas. This is a physical change, not a chemical reaction.

Identifying the Process Without Chemical Reaction

Based on the analysis:

• Cloth cleaning using detergent involves chemical interaction.
• Ripening of mango is a series of biological chemical reactions.
• Change of colour of turmeric due to soap is a chemical (acid-base) reaction.
• Cooling effect of nail polish remover is due to evaporation, a physical change.

Therefore, the process that does NOT involve a chemical reaction is the cooling effect of nail polish remover.

Revision Table: Chemical vs. Physical Changes

Additional Information on Physical Processes and Chemical Reactions

It is important for students to be able to distinguish between physical changes and chemical reactions as this is a fundamental concept in chemistry. Physical changes involve alterations to the form or appearance of a substance, but not its fundamental nature. The molecules themselves do not change into different types of molecules. Examples include changes of state (solid, liquid, gas), changes in size or shape, and mixing substances without a reaction occurring.

Chemical reactions, on the other hand, involve the breaking and forming of chemical bonds, resulting in the creation of new substances with different properties. Signs that a chemical reaction might have occurred include a change in colour, formation of a gas (bubbles), formation of a precipitate (solid), release or absorption of heat (temperature change), or emission of light.

Evaporation, as seen in the case of nail polish remover's cooling effect, is purely a physical process. The liquid molecules gain enough energy to overcome the intermolecular forces holding them together in the liquid state and escape into the gas phase. The acetone (or ethyl acetate) molecules remain acetone (or ethyl acetate) molecules, just in a different state.