Matter & Mixtures — Set 3

Correct Answer: A. Gas

• **Gas particles** = Move rapidly and randomly, possessing the highest kinetic energy among the three common states. • **Particle freedom** — In gases, particles are far apart and experience minimal intermolecular attractions. • 💡 Wrong-option analysis: B: Liquid particles have moderate kinetic energy; C: Bose-Einstein has lowest kinetic energy; D: Solid particles have lowest kinetic energy.

Correct Answer: C. Alcohol

• **Alcohol solvent** = Tincture of iodine is prepared by dissolving iodine in ethanol, a common antiseptic solution. • **Medical use** — This solution is applied topically to minor wounds and cuts. • 💡 Wrong-option analysis: A: Ether is volatile and not suitable for medical use; B: Chloroform is toxic; D: Iodine is poorly soluble in water.

Correct Answer: B. Oxygen

• **Element definition** = Oxygen is the simplest form of matter that cannot be further decomposed chemically. • **Fundamental particle** — An element consists of atoms of the same type that cannot be broken down. • 💡 Wrong-option analysis: A: Carbon dioxide can be decomposed into carbon and oxygen; C: Sodium chloride can be decomposed into sodium and chlorine; D: Water can be decomposed into hydrogen and oxygen.

Correct Answer: A. It remains constant

• **Temperature plateau** = During phase change, temperature remains constant because heat energy breaks intermolecular bonds. • **Latent heat** — This energy is called latent heat and does not increase particle kinetic energy. • 💡 Wrong-option analysis: B: Temperature increases before and after phase change; C: Temperature does not fluctuate during phase change; D: Temperature decreases during cooling phase change.

Correct Answer: B. High compressibility

• **Compressibility property** = Gases are highly compressible because there are large spaces between their particles. • **Volume reduction** — Applying pressure reduces the space between particles significantly. • 💡 Wrong-option analysis: A: Gases have no fixed volume; C: Gases have no definite shape; D: Gases have weak intermolecular forces.

Correct Answer: B. Solute

• **Solute definition** = Salt is the substance being dissolved in the liquid solvent. • **Dissolved substance** — The solute is present in lesser amount compared to the solvent in the solution. • 💡 Wrong-option analysis: A: Suspension involves larger visible particles; C: Catalyst speeds up reactions; D: Solvent dissolves the solute.

Correct Answer: A. Fractional distillation

• **Fractional distillation method** = Used because gases in air have different boiling points like nitrogen (-196°C) and oxygen (-183°C). • **Separation process** — Air is first liquefied, then warmed slowly to separate components based on boiling points. • 💡 Wrong-option analysis: B: Simple distillation cannot separate gases with similar boiling points; C: Evaporation is not suitable for air separation; D: Filtration cannot separate gases.

Correct Answer: D. Bromine

• **Bromine property** = The only non-metal that remains in a liquid state at standard room temperature and pressure. • **Reddish-brown color** — Known for its distinctive reddish-brown appearance and pungent odor. • 💡 Wrong-option analysis: A: Chlorine is a gas at room temperature; B: Mercury is a metal, not a non-metal; C: Iodine is a solid at room temperature.

Correct Answer: D. Melting point

• **Melting point test** = Pure substances have sharp and specific melting or boiling points. • **Impurity effect** — Impurities lower the melting point or cause a range of temperatures rather than a single point. • 💡 Wrong-option analysis: A: Surface area does not indicate purity; B: Volume varies with state; C: Mass alone does not show purity.

Correct Answer: B. Chalk powder in water

• **Suspension definition** = Chalk powder in water has large visible particles that remain dispersed without dissolving. • **Particle settling** — If left undisturbed, particles eventually settle due to gravity. • 💡 Wrong-option analysis: A: Milk is a colloid/emulsion; C: Salt in water is a true solution; D: Blood is a colloid.