Explanation: When salt is added to pure water, its boiling point increases. This phenomenon is known as boiling point elevation, a colligative property. The presence of dissolved salt particles reduces the vapor pressure of water, requiring a higher temperature for it to boil.

Explanation: A rainbow is formed due to the dispersion of sunlight into its constituent colors and total internal reflection inside water droplets in the atmosphere. The light entering a droplet is refracted, reflected internally, and then refracted again as it exits, producing the beautiful spectrum of colors.

Explanation: The Montreal Protocol, signed in 1987, is an international agreement aimed at protecting the ozone layer by phasing out the production and use of ozone-depleting substances (ODS) such as chlorofluorocarbons (CFCs) and halons. It is one of the most successful environmental treaties in history.

Explanation: All enzymes are proteins (except a few RNA-based enzymes called ribozymes). Enzymes act as biological catalysts that speed up chemical reactions in living organisms without being consumed in the process. They work by lowering the activation energy of reactions, ensuring that metabolic processes occur efficiently at normal body temperatures. Each enzyme is specific to a particular substrate, forming an enzyme-substrate complex to carry out its function effectively.

Explanation: According to the Bureau of Indian Standards (BIS) – IS 10500:2012, the acceptable limit of total hardness in drinking water, expressed as CaCO₃, is 200 mg/l. The permissible limit in the absence of an alternate source is up to 600 mg/l. Excess hardness can cause scaling and affect the taste of water.

Explanation: Wind energy is a clean and renewable source of energy that does not cause environmental pollution. It is generated by converting the kinetic energy of moving air into mechanical or electrical energy using wind turbines. Unlike fossil fuels such as coal or mineral oil, wind energy does not release carbon dioxide, sulfur dioxide, or other greenhouse gases. It is, therefore, a pollution-free and sustainable source of power, widely used for electricity generation in wind farms.

When an ant bites, it releases formic acid (HCOOH) into the skin. This acid causes a sharp burning sensation, redness, and irritation at the site of the bite. The name “formic” comes from the Latin word “formica”, meaning ant, as the acid was first extracted from ants. The pain can be neutralized by applying a mild base like baking soda (sodium bicarbonate).

Other options (for context)

• Hydrochloric Acid: Found in the human stomach, aids digestion.
• Acetic Acid: Main component of vinegar, not involved in ant bites.
• Phosphoric Acid: Used in fertilizers and soft drinks, not produced by ants.

Explanation: Bryology is the branch of botany that deals with the study of bryophytes, which include mosses and liverworts. These are small, non-vascular plants that typically grow in moist and shady environments.

Explanation: Mercury is used in clinical thermometers mainly because it is a good conductor of heat, allowing it to quickly reach the temperature of the patient’s body. Additionally, it has a uniform rate of expansion, remains liquid over a wide temperature range, and has a shiny appearance for easy visibility of the reading.

Explanation: Smallpox is a highly contagious and deadly disease caused by the Variola virus. It is characterized by high fever, fatigue, and a distinctive pustular rash on the skin. Smallpox was one of the most devastating diseases in human history, but thanks to the worldwide vaccination campaign led by the World Health Organization (WHO), it was officially eradicated in 1980. The vaccine for smallpox was first developed by Edward Jenner in 1796.