Correct Answer: A

Rationale: In a single bond, two atoms share one pair of electrons. This shared pair of electrons is what holds the atoms together in the bond. Therefore, the correct answer is A: 1. Choices B, C, and D are incorrect because they do not represent the number of electron pairs shared in a single bond.

Correct Answer: A

Rationale: In a single bond, two atoms share one pair of electrons. This shared pair of electrons is what holds the atoms together in the bond. Therefore, the correct answer is A: 1. Choices B, C, and D are incorrect because they do not represent the number of electron pairs shared in a single bond.

Correct Answer: C

Rationale: Covalent bonds, especially those formed between non-metals, are the strongest type of chemical bond. In covalent bonds, atoms share electrons, creating a strong bond that requires a significant amount of energy to break. Choice A, ionic bonds, are strong but generally weaker than covalent bonds as they involve the transfer of electrons rather than sharing. Choice B, hydrogen bonds, are relatively weak intermolecular forces, not true chemical bonds. Choice D, metallic bonds, are strong but typically not as strong as covalent bonds. Metallic bonds involve a 'sea of electrons' shared between metal atoms, providing strength but with less directional bonding compared to covalent bonds.

Correct Answer: B

Rationale: Matter that has a definite shape and volume is referred to as a solid. Solids maintain their shape and volume under normal conditions, unlike liquids that have a definite volume but take the shape of their container, gases that have neither a definite shape nor volume, and plasma which is a state of matter with no definite shape or volume and consists of charged particles.

Correct Answer: C

Rationale: Increasing the surface area of a reactant leads to more particles being exposed to the reaction, which in turn increases the reaction rate. This is because a larger surface area provides more sites for collisions between reacting particles, resulting in a higher frequency of successful collisions and thus accelerating the reaction. Choice A, 'Decreases the reaction rate,' is incorrect because increasing surface area actually accelerates the reaction. Choice B, 'Has no effect,' is incorrect as increasing surface area does have a significant effect on the reaction rate. Choice D, 'Stops the reaction,' is incorrect as increasing surface area does not stop the reaction but rather enhances it.