Which of the following is a common property of both acids and bases?

Correct Answer: D

Rationale: The correct answer is D. Both acids and bases can conduct electricity when dissolved in water. Acids ionize in water to produce H+ ions, which can carry an electric current, while bases ionize to produce OH- ions, which also conduct electricity. The other options are not common properties of both acids and bases. Reacting with metals to produce hydrogen gas is characteristic of acids, tasting sour is a property of acids, and turning blue litmus paper red is a property of bases, not a common property shared by both.

Correct Answer: B

Rationale: Friction is a force that opposes motion when two surfaces are in contact. It acts in the opposite direction to the direction of motion, causing objects to slow down or come to a stop. Therefore, friction decreases speed rather than increasing it. Choice A is incorrect as friction does not increase speed but rather hinders it. Choice C is incorrect because friction does have an impact on speed by slowing down objects. Choice D is incorrect as friction's effect is not making objects float but rather causing resistance to motion.

Correct Answer: C

Rationale: An unbalanced force acting on an object at rest will cause the object to move into motion. This is in accordance with Newton's first law of motion, which states that an object at rest will remain at rest unless acted upon by an external force. Therefore, option C, 'It moves the object into motion,' is the correct answer. Choices A and B are incorrect because an unbalanced force disrupts the object's state of rest. Choice D is incorrect as force does not affect the mass of an object.

Correct Answer: A

Rationale: According to Newton's second law of motion, acceleration is directly proportional to the net force applied to an object when mass is constant. Therefore, if the net force is doubled, the acceleration of the object will also double. This relationship is expressed by the formula F=ma, where F is the net force, m is the mass, and a is the acceleration. When mass is constant, doubling the force applied will result in a proportional doubling of acceleration. Choices B, C, and D are incorrect because doubling the net force does not halve, maintain, or quadruple the acceleration; it directly and proportionally increases the acceleration.

Correct Answer: A

Rationale: - Primary structure refers to the linear sequence of amino acids in a protein. - Secondary structure refers to local folded structures within a protein, such as alpha helices and beta sheets. - Tertiary structure is the overall 3D shape of a protein, which is determined by interactions between amino acid side chains and the environment. - Quaternary structure refers to the arrangement of multiple protein subunits in a protein complex. Therefore, the 3D structure of a protein is called the tertiary structure because it represents the overall folding of the protein into a specific shape.