Correct Answer: A

Rationale: The correct answer is A: Decomposition reaction. A decomposition reaction involves breaking down a compound into its components. During this reaction, a single compound breaks down into two or more simpler substances. This process is the opposite of a synthesis reaction where multiple substances combine to form a more complex compound. Choices B, C, and D are incorrect because combustion reaction involves burning a substance in oxygen, neutralization reaction involves the reaction between an acid and a base to form water and a salt, and single displacement reaction involves an element displacing another in a compound.

Correct Answer: C

Rationale: The correct answer is C: Argon. Argon is a noble gas, part of Group 18 in the periodic table. Noble gases are colorless, odorless, and typically non-reactive under normal conditions. Other elements in this group include helium, neon, krypton, xenon, and radon. Argon finds wide applications in welding, lighting, and scientific research. Choices A, B, and D are not noble gases. Hydrogen is a non-metal, Fluorine is a halogen, and Nitrogen is a diatomic non-metal gas.

Correct Answer: B

Rationale: The correct answer is 'Halogens.' Halogens are a group of elements that include chlorine, fluorine, and iodine. These elements are part of Group 17 in the periodic table. They share similar properties such as high reactivity and the ability to readily form compounds. Choice A, 'Alkali metals,' is incorrect as alkali metals are found in Group 1 of the periodic table, which includes elements like lithium and sodium. Choice C, 'Transition metals,' is incorrect as transition metals are located in the middle section of the periodic table, not in Group 17. Choice D, 'Noble gases,' is incorrect as noble gases are in Group 18 and include elements like helium and neon, which are chemically inert.

Correct Answer: A

Rationale: A colligative property is a property that depends on the number of solute particles in a solution, not on the identity of the solute particles. Freezing point depression is one such property, where adding a solute to a solvent lowers the freezing point of the solution compared to the pure solvent. This phenomenon occurs because the presence of solute particles disrupts the formation of the regular crystal lattice structure, requiring a lower temperature for solidification to occur. Choices B, C, and D are not colligative properties. Viscosity and surface tension are not dependent on the number of solute particles but on intermolecular forces and molecular interactions. Boiling point elevation is another colligative property, but in this case, the question asked for a colligative property of a solution, making freezing point depression the correct answer.

Correct Answer: C

Rationale: The correct answer is 'Evaporation.' This phase change occurs when a liquid turns into a gas. During evaporation, molecules gain enough energy to break free from the liquid phase and enter the gas phase, without the need for the liquid to reach its boiling point. Choice A, 'Condensation,' is the opposite phase change where gas turns into a liquid. Choice B, 'Sublimation,' is the phase change from solid directly to gas, skipping the liquid phase. Choice D, 'Melting,' is the phase change from solid to liquid.