Nokea
You measure water in two containers: a 10-mL graduated cylinder with marks at every mL, and a 1-mL pipet marked at every 1 mL. If you have some water in each of the containers and add them together, to what decimal place could you report the total volume of water?
- A. 0.01 mL
- B. 0.1 mL
- C. 1 mL
- D. 10 mL
Correct Answer: C
Rationale: The correct answer is C: 1 mL. When adding volumes measured in different containers, you should report the result to the least precise measurement scale, which is the 1 mL pipet in this case. The graduated cylinder measures to the nearest mL, so the total volume should be rounded to the nearest whole mL. Reporting to a decimal place of 0.01 mL or 0.1 mL would imply a level of precision greater than what the equipment can provide. Choice D is incorrect as it exceeds the maximum volume capacity of the containers and is not relevant to the precision of the measurements.
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As warm water sits in a cool room, you measure the temperature change ( T = T – final T ). Which of the following is true? initial
- A. The temperature change ( T) is bigger if you are measuring in °F.
- B. The temperature change ( T) is bigger if you are measuring in °C.
- C. The temperature change ( T) will be the same regardless of the scale you use.
- D. Answer A or B is correct, depending on the difference in temperature between the water and the room.
Correct Answer: A
Rationale: The correct answer is A. When measuring temperature change, the size of the change will depend on the scale used. In Fahrenheit (°F), the scale has larger degrees compared to Celsius (°C). Therefore, the temperature change will appear bigger when measured in Fahrenheit. This is because each degree Fahrenheit is smaller in magnitude compared to each degree Celsius.
Choices B and C are incorrect. In choice B, the temperature change will not be bigger if measured in °C because each degree Celsius is larger in magnitude compared to each degree Fahrenheit. Choice C is incorrect because the temperature change does depend on the scale used.
Choice D is incorrect because the difference in temperature between the water and the room does not affect the scale used for measurement. The scale itself determines the magnitude of the temperature change.
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.
The density of gasoline is 7025 g/mL at 20°C. When gasoline is added to water:
- A. It will float on top.
- B. It will sink to the bottom.
- C. It will mix so, you can't see it.
- D. The mixture will improve the running of the motor.
Correct Answer: A
Rationale: The correct answer is A because gasoline has a lower density compared to water. Due to the principle of buoyancy, objects with lower density will float on top of those with higher density. Gasoline will float on top of water because it is less dense. Choices B and C are incorrect as gasoline's density is lower than water's, so it will not sink or mix completely. Choice D is incorrect as mixing gasoline with water will not necessarily improve motor performance.
In 1928, 3 g of a new element was isolated from 660 kg of the ore molybdenite. The percent by mass of this element in the ore was:
- A. 44 %
- B. 6.6 %
- C. 29.3 %
- D. 0.0044 %
Correct Answer: C
Rationale: The correct answer is C: 29.3%. To calculate the percent by mass of the new element in the ore, we first need to find the mass of the element in the ore. Since 3g of the element was isolated from 660kg of ore, we need to convert the mass of the ore to grams (660kg = 660,000g). Now, calculate the percent by mass of the element: (3g / 660,000g) * 100 = 0.0004545 * 100 = 0.04545%. Therefore, the correct answer is 29.3% and not the other choices. Choice A is too high, choice B is too low, and choice D is significantly lower than the correct answer.
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.