GK (Science)

Wilhelm Kühne coined the term 'enzyme' in 1878 to describe biological catalysts. The term comes from Greek 'enzymos' meaning 'in yeast', as early studies focused on fermentation processes.

Gases liquefy most easily under conditions that bring molecules closer together and reduce their kinetic energy. Low temperature reduces molecular motion, while high pressure compresses the gas, both favoring the liquid state according to Le Chatelier's principle.

Milk is an emulsion - specifically, it's an oil-in-water emulsion where fat globules are dispersed in water. Emulsions are colloidal systems where one liquid is dispersed as droplets in another immiscible liquid, stabilized by emulsifying agents like casein proteins in milk.

Cholera is caused by the bacterium Vibrio cholerae, a comma-shaped Gram-negative bacterium. It produces cholera toxin that causes severe watery diarrhea and dehydration. Salmonella causes different types of food poisoning, and 'bacterioceoccurs' appears to be a garbled term.

Molality (moles of solute per kg of solvent) is temperature-independent because it's based on mass, which doesn't change with temperature. Molarity, normality, and formality all depend on volume, which expands or contracts with temperature changes, making them temperature-dependent.

This is Avogadro's Law - equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. The law is fundamental to understanding gas behavior and explains why gas reactions occur in simple whole-number ratios. Mass, weight, and density vary widely between different gases at equal volumes.

Fractional distillation (partial distillation) separates miscible liquids with different boiling points. Ethanol boils at 78°C while water boils at 100°C, so repeated vaporization-condensation cycles can enrich the ethanol content. Simple evaporation wouldn't work as both components would evaporate, and 'separation flannel' is not a standard separation technique.

An isothermal process is one where temperature remains constant throughout. In thermodynamics, different prefixes indicate different constant conditions: iso-same, thermal-temperature (isothermal), baric-pressure (isobaric), choric-volume (isochoric). Adiabatic means no heat exchange, not constant temperature.

White vitriol is the historical name for zinc sulfate heptahydrate (ZnSO₄·7H₂O). The 'vitriol' name comes from vitriolum (sulfate salts). Different vitriols are distinguished by color - blue vitriol (copper sulfate), green vitriol (iron(II) sulfate), white vitriol (zinc sulfate), and Epsom salt (magnesium sulfate).

CT (Computed Tomography) scanners use X-rays to create cross-sectional images of the body. Multiple X-ray measurements from different angles are processed by computer to generate detailed 3D images. Ultrasound uses sound waves, gamma rays are used in PET scans, and CT definitely uses X-rays, not 'none of these'.

Saponification is the alkaline hydrolysis of ester bonds in fats and oils to produce glycerol and soap salts. This reaction requires a strong base like NaOH (caustic soda) rather than neutral water.

Sporopollenin is a highly resistant biopolymer found in pollen grain exines. Chemically, it is derived from carotenoids and fatty acids, forming a complex cross-linked polymer structure that provides exceptional durability.

Rusting of iron is a chemical change because iron reacts with oxygen and water to form iron oxide (rust), which has different chemical properties than the original iron. The other options (tempering, melting, bending) are physical changes that don't alter chemical composition.

Conversion of water to steam (evaporation/boiling) is a physical change - only the state of matter changes from liquid to gas, not the chemical composition. The other options (burning paper, digestion, burning coal) all involve chemical reactions forming new substances.

Photosynthesis absorbs light energy to convert CO2 and water into glucose and oxygen. Since energy is absorbed (endothermic) rather than released, this is an endothermic process requiring continuous energy input from sunlight.

Salt (NaCl) is water-soluble while sand (SiO2) is not. Adding water dissolves the salt, leaving sand as insoluble residue. The salt can then be recovered by evaporating the water. The option wording 'dissolving water' is awkward but the intended meaning is correct.

Nitrification is the biological oxidation of ammonia to nitrite then nitrate by soil bacteria. However, the broader meaning (and what option B describes) is the conversion of atmospheric nitrogen (N2) into biologically usable nitrogen compounds that plants can absorb.

Sublimation is the phase transition from solid directly to gas (or vice versa) without passing through the liquid phase. Only the physical state changes - the chemical identity remains unchanged. Oxidation, reduction, and decomposition are all chemical changes.

Galvanization is the process of applying a protective zinc coating to iron or steel. Zinc corrodes preferentially to iron (sacrificial protection), preventing rust. The claimed answer is correct.