The numbers of protons, neutrons, and electrons in K+ are: A) 20 p, 19 n, 19 e

Correct Answer: C

Rationale: The correct answer is C: 19 p, 20 n, 19 e. K+ has an atomic number of 19, indicating 19 protons. Since it is a potassium ion with a +1 charge, it lost one electron, giving it 19 electrons instead of the usual 20. The number of neutrons is found by subtracting the atomic number from the mass number (39 for potassium) to get 20 neutrons. Option A is incorrect due to the incorrect number of electrons. Option B has the incorrect number of protons. Option D has the incorrect number of electrons.

Correct Answer: A

Rationale: The correct answer is A because a quantitative observation must contain both a number and a unit to provide a specific measurement. This ensures the observation is precise and can be accurately communicated. The other choices are incorrect because B is vague, C is not a requirement for quantitative observations, and D is not true as quantitative observations can also be obtained through measurements, not just experimentation.

Correct Answer: D

Rationale: The correct answer is D: natural law. A natural law describes a consistent pattern or behavior in the natural world, such as the conservation of mass in a chemical reaction. This principle states that the total mass of materials before and after a chemical change remains constant. Observations (A) are factual statements based on data, measurements (B) involve quantifying properties, and theories (C) are explanations based on evidence, but none specifically address the consistent behavior of mass in chemical changes as a natural law does.

Correct Answer: D

Rationale: The correct answer is D: kilometer. A kilometer is a metric unit for length because it is used to measure long distances. In the metric system, length is typically measured in meters, and a kilometer is equal to 1000 meters. This makes it a suitable unit for measuring larger distances efficiently. Explanation for incorrect choices: A: Gram is a unit of mass, not length. B: Milliliter is a unit of volume, not length. C: Yard is a unit of length, but it is not a metric unit. The metric system uses meters and its derivatives for length measurements.

Correct Answer: A

Rationale: The correct answer is A: mass. Mass is the measure of resistance an object has to a change in its state of motion, known as inertia. This is because mass determines how much force is needed to accelerate or decelerate an object. Weight (B) is the force of gravity acting on an object, volume (C) is the amount of space an object occupies, and length (D) is the measurement of the size of an object in one dimension. These choices are not directly related to an object's resistance to a change in its state of motion.