Nokea
We generally report a measurement by recording all of the certain digits plus uncertain digit(s).
- A. no
- B. one
- C. two
- D. three
Correct Answer: B
Rationale: Step 1: In measurement, certain digits are the numbers that are known for sure.
Step 2: Uncertain digits are the last digit that is estimated or measured.
Step 3: We record all the certain digits and one uncertain digit to indicate the precision of the measurement.
Step 4: Choice A is incorrect because we do include uncertain digit(s) in the measurement.
Step 5: Choice C and D are incorrect as including two or three uncertain digits would provide excessive precision beyond what is known for certain.
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In March 2008, gold reached a milestone value of $1000 per troy ounce. At that price, what was the cost of a gram of gold? (1 troy ounce = 10 g)
- A. less than $1
- B. between $1 and $10
- C. between $10 and $50
- D. between $50 and $100
Correct Answer: C
Rationale: To find the cost of a gram of gold at $1000 per troy ounce, we divide $1000 by 10 (since 1 troy ounce = 10g). This gives us $100 per gram. Therefore, the correct answer is C: between $10 and $50. Option A is incorrect as it is less than $1, option B is incorrect as it is between $1 and $10, and option D is incorrect as it is between $50 and $100.
Convert 4 lb to g. (1 lb = 6 g)
- A. 7.58 10 2 g
- B. 1.56 103 g
- C. 7.58 104 g
- D. 1.56 102 g
Correct Answer: C
Rationale: To convert 4 lb to g, we use the conversion factor provided: 1 lb = 6 g.
1. Multiply 4 lb by 6 g/lb: 4 lb * 6 g/lb = 24 g.
2. Since the question asks for the answer in grams, the correct conversion is 24 g.
Therefore, the correct answer is C (7.58 x 10^4 g).
Other choices are incorrect because they do not correctly apply the conversion factor or provide the accurate conversion from pounds to grams.
Many classic experiments have given us indirect evidence of the nature of the atom. Which of the experiments listed below did not give the results described?
- A. The Rutherford experiment proved the Thomson "plum- pudding" model of the atom to be essentially correct.
- B. The Rutherford experiment was useful in determining the nuclear charge on the atom.
- C. Millikan's oil-drop experiment showed that the charge on any particle was a simple multiple of the charge on the electron.
- D. The electric discharge tube proved that electrons have a negative charge.
Correct Answer: A
Rationale: The correct answer is A because the Rutherford experiment actually disproved the Thomson "plum-pudding" model of the atom. Rutherford's experiment involved firing alpha particles at a thin gold foil and observing their scattering patterns. The results showed that atoms have a small, dense, positively charged nucleus, which contradicted the Thomson model. Choice B is correct as the experiment was indeed useful in determining the nuclear charge on the atom. Choice C is incorrect because Millikan's oil-drop experiment determined the charge on the electron, not just that it was a simple multiple. Choice D is incorrect as the electric discharge tube did show that electrons have a negative charge.
A metric unit for length is
- A. gram
- B. milliliter
- C. yard
- D. kilometer
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.
The statement “The total mass of materials is not affected by a chemical change in thosematerials” is called a(n)
- A. observation
- B. measuremen t
- C. theory
- D. natural law
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.