Salt water causes marine ecosystems to be very different from freshwater ecosystems. Organisms in both types of ecosystems are affected by the freezing and melting of ice. An experiment was conducted to test the hypothesis that ice melts faster in salt water than in fresh water. Ice cubes made of fresh water were placed into cups containing either fresh water or salt water. Various data were recorded, and the energy released by each melting ice cube was calculated from the data. The table shows the results for each cup.
What statement describes one or more needed changes to this experiment that would allow the experimenter to draw a valid conclusion?
- A. Salt water should have been used to make the ice cubes for the cup of salt water.
- B. The time for ice cubes to melt should have been measured in minutes.
- C. At the beginning, both cups should have contained the same mass of water at the same temperature.
- D. The energy released should have been measured, not calculated.
Correct Answer & Rationale
Correct Answer: C
Option C highlights the necessity for both cups to start with the same mass of water at the same temperature to ensure a fair comparison. This control eliminates variables that could skew results, allowing for a valid conclusion about the melting rates of ice cubes in different solutions. Option A is incorrect because using salt water to make ice cubes would not provide relevant data on how the ice behaves in fresh versus salt water. Option B is not a change that affects the experimental validity; measuring time in minutes is appropriate, but the key is ensuring conditions are equal. Option D suggests a measurement method change, but calculating energy based on temperature changes is acceptable in this context.
Option C highlights the necessity for both cups to start with the same mass of water at the same temperature to ensure a fair comparison. This control eliminates variables that could skew results, allowing for a valid conclusion about the melting rates of ice cubes in different solutions. Option A is incorrect because using salt water to make ice cubes would not provide relevant data on how the ice behaves in fresh versus salt water. Option B is not a change that affects the experimental validity; measuring time in minutes is appropriate, but the key is ensuring conditions are equal. Option D suggests a measurement method change, but calculating energy based on temperature changes is acceptable in this context.
Other Related Questions
A diagram of a PV cell being exposed to sunlight is shown below. Click on the labels you want to select and drag them into the boxes to show the components of the PV cell.
- A. Phosphorus-injected layer
- B. Boron-injected layer
- C. Electric field
- D. Energy
Correct Answer & Rationale
Correct Answer: A,B,C
The components of a photovoltaic (PV) cell include the phosphorus-injected layer, which serves as the n-type semiconductor, and the boron-injected layer, acting as the p-type semiconductor. Together, these layers create a junction that facilitates the movement of electrons when exposed to sunlight. The electric field between these layers is crucial for separating charge carriers, enabling electricity generation. Option D, "Energy," is not a structural component of the PV cell but rather a result of its operation. It does not represent a physical part of the cell, making it an incorrect choice.
The components of a photovoltaic (PV) cell include the phosphorus-injected layer, which serves as the n-type semiconductor, and the boron-injected layer, acting as the p-type semiconductor. Together, these layers create a junction that facilitates the movement of electrons when exposed to sunlight. The electric field between these layers is crucial for separating charge carriers, enabling electricity generation. Option D, "Energy," is not a structural component of the PV cell but rather a result of its operation. It does not represent a physical part of the cell, making it an incorrect choice.
What is the relationship between the kinetic energy of the feather and of the hammer just before they hit the surface of the Moon?
- A. The hammer has more kinetic energy than the feather because it has a greater mass.
- B. Both objects have the same kinetic energy because they fell with the same velocity.
- C. The hammer has more kinetic energy than the feather because it will accelerate faster than the feather.
- D. Both objects have the same kinetic energy because gravity pulls on both objects equally.
Correct Answer & Rationale
Correct Answer: A
The hammer possesses more kinetic energy than the feather due to its greater mass, as kinetic energy is calculated using the formula KE = 0.5 * mass * velocity². While both objects fall at the same rate in a vacuum, their velocities are equal, but the hammer’s larger mass results in higher kinetic energy. Option B is incorrect because, although they have the same velocity, kinetic energy also depends on mass. Option C misrepresents the situation; both objects accelerate at the same rate in a vacuum. Option D is misleading; while gravity affects both equally, it does not determine kinetic energy, which also requires consideration of mass.
The hammer possesses more kinetic energy than the feather due to its greater mass, as kinetic energy is calculated using the formula KE = 0.5 * mass * velocity². While both objects fall at the same rate in a vacuum, their velocities are equal, but the hammer’s larger mass results in higher kinetic energy. Option B is incorrect because, although they have the same velocity, kinetic energy also depends on mass. Option C misrepresents the situation; both objects accelerate at the same rate in a vacuum. Option D is misleading; while gravity affects both equally, it does not determine kinetic energy, which also requires consideration of mass.
What natural process is required to connect the ice core data to the Tunguska Event?
- A. the cycling of carbon in forest fires
- B. the interaction of comets with the solar wind
- C. the movement of glaciers due to gravity
- D. the constant mixing of the atmosphere
Correct Answer & Rationale
Correct Answer: D
Connecting ice core data to the Tunguska Event necessitates understanding atmospheric dynamics, which is achieved through the constant mixing of the atmosphere. This mixing disperses particles and gases, allowing researchers to correlate ice core samples with historical events, including the Tunguska explosion. Option A, the cycling of carbon in forest fires, is unrelated to the atmospheric conditions or the specific data derived from ice cores. Option B, the interaction of comets with the solar wind, pertains to space phenomena rather than terrestrial atmospheric processes. Option C, the movement of glaciers due to gravity, describes glacial dynamics but does not address the atmospheric mixing needed to link ice core data to the event.
Connecting ice core data to the Tunguska Event necessitates understanding atmospheric dynamics, which is achieved through the constant mixing of the atmosphere. This mixing disperses particles and gases, allowing researchers to correlate ice core samples with historical events, including the Tunguska explosion. Option A, the cycling of carbon in forest fires, is unrelated to the atmospheric conditions or the specific data derived from ice cores. Option B, the interaction of comets with the solar wind, pertains to space phenomena rather than terrestrial atmospheric processes. Option C, the movement of glaciers due to gravity, describes glacial dynamics but does not address the atmospheric mixing needed to link ice core data to the event.
Based on the table, use the drop-down menus to make the following statement correct. _ experiences the least warming effect from CO2 because it has the _ of CO2 in its atmosphere.
- A. smallest amount
- B. largest amount
- C. Mars
- D. Planet L
Correct Answer & Rationale
Correct Answer: A,C
The statement highlights that Mars experiences the least warming effect from CO2 due to its atmospheric composition. Mars has a small amount of CO2 compared to other planets, which limits its greenhouse effect and consequently its warming. Option B, "largest amount," is incorrect as it contradicts the premise that a larger CO2 presence would lead to more warming. Option D, "Planet L," is not a recognized celestial body in this context and does not provide relevant information regarding CO2 levels. Thus, the combination of Mars with the smallest amount of CO2 accurately reflects the relationship between atmospheric composition and warming effects.
The statement highlights that Mars experiences the least warming effect from CO2 due to its atmospheric composition. Mars has a small amount of CO2 compared to other planets, which limits its greenhouse effect and consequently its warming. Option B, "largest amount," is incorrect as it contradicts the premise that a larger CO2 presence would lead to more warming. Option D, "Planet L," is not a recognized celestial body in this context and does not provide relevant information regarding CO2 levels. Thus, the combination of Mars with the smallest amount of CO2 accurately reflects the relationship between atmospheric composition and warming effects.