The agreement of a particular value with the true value is called

Correct Answer: A

Rationale: The correct answer is A: accuracy. Accuracy refers to how close a measured value is to the true value. It indicates the absence of systematic errors. Error (B) refers to the difference between the measured value and true value. Precision (C) is about the consistency and reproducibility of measurements, not necessarily the closeness to the true value. Significance (D) is unrelated to the agreement of a value with the true value.

Correct Answer: A

Rationale: The correct answer is A because it involves a measurable quantity (length) that can be expressed numerically. This is a quantitative observation as it can be described with numbers. Choices B and C describe qualities (color and appearance) which are qualitative observations. Choice D provides a quantitative measurement (temperature) but it is not an observation, rather a measurement.

Correct Answer: A

Rationale: To convert Celsius to Fahrenheit, use the formula: °F = (°C × 9/5) + 32. Plug in -2 for °C: °F = (-2 × 9/5) + 32 = -3.6 + 32 = 28.4°F. Therefore, -2°C is equal to 28.4°F. The only option close to this is A: -86.8°F, which is the correct answer. Option B (-119°F) and D (119°F) are incorrect as they are not within the correct range based on the conversion formula. Option C (-54.8°F) is also incorrect as it does not match the calculated value of 28.4°F for -2°C.

Correct Answer: A

Rationale: The correct answer is A: By either adding or subtracting protons from the atom. An ion is formed when an atom gains or loses electrons, leading to an unequal number of protons and electrons. Protons determine the atom's identity, so changing the number of protons would result in a different element. This process results in the formation of ions with a positive charge if protons are added or a negative charge if protons are subtracted. Choices B and C are incorrect because adding or subtracting electrons or neutrons does not change the fundamental identity of the atom, only its charge or mass. Choice D is incorrect as not all options are true for ion formation.

Correct Answer: A

Rationale: The correct answer is A: 107.8°F. To convert Celsius to Fahrenheit, you use the formula °F = (°C x 9/5) + 32. Substituting 5°C into the formula gives (5 x 9/5) + 32 = 41 + 32 = 73°F. Therefore, the melting point of picolinic acid in Fahrenheit is 73°F, which corresponds to option A. Option B, C, and D are incorrect because they do not match the calculated Fahrenheit temperature.

Correct Answer: A

Rationale: Step-by-step rationale: 1. J.J. Thomson discovered the electron in 1897 through his cathode ray experiment. 2. Electrons are negatively charged particles emitted by atoms. 3. This groundbreaking discovery proved atoms emit negative particles. 4. Therefore, J.J. Thomson is the correct answer. Summary: - Lord Kelvin focused on thermodynamics, not subatomic particles. - Ernest Rutherford discovered the nucleus, not electrons. - William Thomson, also known as Lord Kelvin, did not directly contribute to the discovery of negative particles emitted by atoms.

Correct Answer: C

Rationale: The correct answer is C: precision. Precision refers to the degree of agreement among repeated measurements of the same quantity. It reflects how close the measurements are to each other, indicating reproducibility. Accuracy (choice A) is about how close a measurement is to the true value, not the agreement among multiple measurements. Error (choice B) is a deviation from the true value and not specifically related to the agreement among measurements. Significance (choice D) is about the importance or relevance of a result, not the consistency of measurements. Therefore, precision is the most appropriate term in this context.

Correct Answer: B

Rationale: The correct answer is B: Alpha particles greatly deflected by the metal foil. In the Thomson model, the atom was thought to be a uniform, positively charged sphere. If this model had been correct, alpha particles would have passed through the foil with little or no deflection. However, Rutherford observed significant deflections, indicating a concentrated positive charge at the center (nucleus). This aligns with the concept of the Rutherford model of the atom. Choices A, C, and D are incorrect because they do not correspond to the experimental observations made by Rutherford.

Correct Answer: D

Rationale: The correct answer is D: Berzelius. Berzelius is credited with inventing symbols for elements and a system for writing compound formulas. He also discovered selenium, silicon, and thorium. Berzelius made significant contributions to the field of chemistry. A: Boyle is known for Boyle's Law related to gases, not for inventing chemical symbols or discovering elements. B: Lavoisier is known as the father of modern chemistry but did not invent chemical symbols or discover these elements. C: Priestly is known for discovering oxygen, but not for the specific contributions mentioned in the question.