Which material has the smallest specific heat capacity?

Correct Answer: C

Rationale: Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. Among the options provided, aluminum has the smallest specific heat capacity. This means that it requires the least amount of heat to raise its temperature compared to water, wood, and glass. Water has a high specific heat capacity, making it resistant to temperature changes, while wood and glass have higher specific heat capacities compared to aluminum.

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: B

Rationale: An exothermic reaction is characterized by the release of heat. During an exothermic reaction, energy is released in the form of heat to the surroundings, resulting in a temperature increase. This distinguishes it from endothermic reactions, which absorb heat from the surroundings. Choice A is incorrect because exothermic reactions do not absorb heat; instead, they release heat. Choice C is incorrect as exothermic reactions do not remain neutral; they involve a net release of energy. Choice D is incorrect as exothermic reactions do not require energy input; instead, they release energy.

Correct Answer: B

Rationale: The correct answer is B: Condensation. Condensation is the process where gas transforms into a liquid. When gas cools down, it loses energy and its particles come closer, leading to the formation of liquid droplets. Sublimation is the direct transition from solid to gas without passing through the liquid state. Evaporation is the process of liquid turning into a gas, and deposition is the transition of gas directly into a solid. Therefore, choices A, C, and D are incorrect as they describe different phase transitions.

Correct Answer: A

Rationale: The correct answer is 'A: Sour taste.' Acids are known to have a sour taste, which is a fundamental characteristic property of acids. This taste distinguishes acids from bases, which are more likely to have a bitter taste. The sour taste of acids is due to the presence of hydrogen ions in them. Therefore, when identifying an acid based on taste, the sour taste serves as a key indicator. Choices B, C, and D are incorrect. Bitter taste is associated with bases, not acids. While acids do react with bases (Choice C), this is not a characteristic property of acids but rather a chemical behavior. Slippery feel (Choice D) is a property of bases, not acids.

Correct Answer: C

Rationale: The correct answer is 'Ammonia' (Choice C) as it is a common example of a base. Bases are substances that release hydroxide ions (OH-) in aqueous solutions, helping to increase the pH level. Ammonia is a weak base that can accept a proton (H+) to form ammonium hydroxide. In contrast, water (Choice A), sodium chloride (Choice B), and salt (Choice D) are not bases; water is neutral, while sodium chloride and salt are neutral compounds composed of a cation and an anion.

Correct Answer: B

Rationale: Ionic bonds are found in sodium chloride. In an ionic bond, one atom donates an electron to another atom, resulting in the formation of positively and negatively charged ions that are held together by electrostatic forces of attraction. Sodium chloride is a classic example of an ionic compound, where sodium (Na) donates an electron to chlorine (Cl), forming Na+ and Cl- ions that are attracted to each other, creating a crystal lattice structure. Covalent bonds involve the sharing of electron pairs between atoms, which is not the case in sodium chloride. Metallic bonds occur in metals where electrons are delocalized and shared across a lattice, unlike the specific transfer seen in ionic bonds. Hydrogen bonds are a type of intermolecular force, not the primary bond type present in sodium chloride.

Correct Answer: D

Rationale: The correct answer is D, high specific heat. Water's ability to form hydrogen bonds results in a high specific heat capacity, allowing it to absorb and release a large amount of heat energy with minimal temperature change. This property is essential for moderating temperature changes in organisms and maintaining stable environmental conditions for life processes. Choices A, lack of cohesiveness, and C, use as a nonpolar solvent, are incorrect. Water actually has high cohesiveness due to its ability to form hydrogen bonds, and it is a polar solvent, not nonpolar. Choice B, low surface tension, is also incorrect as water's hydrogen bonding contributes to its relatively high surface tension.

Correct Answer: B

Rationale: Enzymes function to speed up reactions by lowering the activation energy required for the reaction to occur. They act as biological catalysts, providing an alternative pathway for the reaction to proceed more rapidly without being consumed in the process. Choices A, C, and D are incorrect because enzymes do not provide energy for reactions (they do not generate energy), their primary function is not to decrease activation energy (though they do lower it), and while they act as catalysts, the primary function is to speed up reactions by lowering activation energy.