G.K. (General Science) - 26

Pure water is a chemical compound consisting of H2O molecules, whereas air and sea water are mixtures of various substances. A mixture contains two or more substances physically combined, while a compound is a pure substance.

Hydrochloric acid (HCl) is a chemical compound formed by the chemical combination of hydrogen and chlorine. Sea water and lime juice are complex mixtures of various solutes and solvents.

Relative humidity is a ratio of the amount of water vapor in the air to the maximum amount the air could hold at that temperature. Because it is a ratio of two identical units, it is dimensionless and has no unit.

Evaporation is a surface phenomenon that occurs at any temperature below the boiling point of a liquid. Boiling, in contrast, occurs only at a specific temperature.

Fractional distillation is the standard industrial process used to separate components of a mixture based on their different boiling points, which is necessary to achieve high purity levels like 99.5 percent.

Sugar is soluble in water, while sand is insoluble. Adding water allows the sugar to dissolve, leaving the sand as a solid residue that can be filtered out.

Latent heat is defined as the energy required to change the state of a unit mass of a substance. The SI unit for energy is Joules (J) and for mass is kilograms (kg), resulting in J/kg.

Freezing is an exothermic process. To transition from a liquid to a solid, the substance must release energy to the surroundings.

Distillation involves heating the solution to evaporate the water and then condensing it back into a liquid, leaving the salt behind. This allows for the complete separation of the solute and solvent.

Ammonium chloride is a substance that undergoes sublimation, meaning it transitions directly from a solid to a gas when heated. This property is used to separate it from non-sublimable solids.

The SI unit of pressure is the Pascal (Pa), which is defined as one Newton per square meter.

The melting point is the specific temperature at which a solid substance begins to transition into a liquid state at a given pressure.

The latent heat of fusion for ice is approximately 3.34 x 10^5 to 3.35 x 10^5 Joules per kilogram. Option C is the standard accepted value.

During phase changes like melting, freezing, and boiling, the temperature of a substance remains constant because the energy supplied is used to overcome intermolecular forces rather than increasing kinetic energy.

To convert Kelvin to Celsius, subtract 273.15. Thus, 300 K - 273 = 27 degrees Celsius.

Mercury, water, and benzene are immiscible liquids with different densities. A separating funnel allows them to be separated based on these density differences.

Naphthalene, iodine, and camphor are substances that undergo sublimation. Butter does not sublime; it melts into a liquid before it can be vaporized.

To convert Celsius to Kelvin, add 273. Thus, 373 + 273 = 646 K.

Water and kerosene are immiscible liquids. A separating funnel is the standard apparatus used to separate two immiscible liquids based on their density difference.

Dry ice (solid CO2) undergoes sublimation, transitioning directly from a solid to a gas at atmospheric pressure.

Evaporation is an endothermic process that absorbs heat from the surroundings, causing a cooling effect. This principle is the basis for how refrigeration systems work.

Fractional crystallization is a method used to separate substances from a mixture based on differences in their solubility at different temperatures.

The energy required to convert a unit mass of a liquid into a vapor at its boiling point is called the latent heat of vaporization.

Ether and alcohol are highly volatile liquids. They evaporate quickly at room temperature, so they must be kept in airtight bottles to prevent loss through evaporation.