A neutral atom always contains an equal number of which of the following?
- A. Protons and electrons
- B. Protons and neutrons
- C. Neutrons and electrons
- D. Protons and alpha particles
Correct Answer & Rationale
Correct Answer: A
A neutral atom contains an equal number of protons and electrons, ensuring that the positive and negative charges balance each other out, resulting in no overall charge. Option B is incorrect because protons and neutrons do not need to be equal; the number of neutrons can vary, leading to different isotopes. Option C is also wrong, as neutrons do not have a charge and do not balance with electrons, which are negatively charged. Lastly, option D is incorrect since alpha particles, which consist of two protons and two neutrons, are not found in neutral atoms and do not play a role in charge balance.
A neutral atom contains an equal number of protons and electrons, ensuring that the positive and negative charges balance each other out, resulting in no overall charge. Option B is incorrect because protons and neutrons do not need to be equal; the number of neutrons can vary, leading to different isotopes. Option C is also wrong, as neutrons do not have a charge and do not balance with electrons, which are negatively charged. Lastly, option D is incorrect since alpha particles, which consist of two protons and two neutrons, are not found in neutral atoms and do not play a role in charge balance.
Other Related Questions
Which of the following is an example of physical weathering?
- A. The cracking of a rock caused by the freezing and thawing of water.
- B. Sediments being transported in a stream.
- C. A sandbar forming in a stream.
- D. Acid rain dissolving a statue.
Correct Answer & Rationale
Correct Answer: A
Physical weathering involves the mechanical breakdown of rocks without changing their chemical composition. Option A exemplifies this, as the freezing and thawing of water causes rocks to crack due to the expansion of ice, a clear physical process. Option B describes sediment transport, which is a process related to erosion rather than weathering. Option C refers to the formation of a sandbar, a depositional feature resulting from sediment accumulation, not weathering. Option D involves chemical weathering, where acid rain alters the chemical structure of the statue, distinguishing it from the physical processes in option A.
Physical weathering involves the mechanical breakdown of rocks without changing their chemical composition. Option A exemplifies this, as the freezing and thawing of water causes rocks to crack due to the expansion of ice, a clear physical process. Option B describes sediment transport, which is a process related to erosion rather than weathering. Option C refers to the formation of a sandbar, a depositional feature resulting from sediment accumulation, not weathering. Option D involves chemical weathering, where acid rain alters the chemical structure of the statue, distinguishing it from the physical processes in option A.
Which of the following is always true of a chemical change?
- A. Color, shape, or texture is altered.
- B. Mass is increased.
- C. A new substance is formed.
- D. Gas or vapor is generated.
Correct Answer & Rationale
Correct Answer: C
A chemical change always results in the formation of a new substance, which is a fundamental characteristic distinguishing it from physical changes. Option A is incorrect because while color, shape, or texture may change, these alterations do not confirm a chemical change unless a new substance is produced. Option B is misleading; mass is conserved in chemical reactions, so it does not necessarily increase. Option D, while often true (as gases can be produced), is not universally applicable; some reactions do not produce gas. Hence, the formation of a new substance is the definitive indicator of a chemical change.
A chemical change always results in the formation of a new substance, which is a fundamental characteristic distinguishing it from physical changes. Option A is incorrect because while color, shape, or texture may change, these alterations do not confirm a chemical change unless a new substance is produced. Option B is misleading; mass is conserved in chemical reactions, so it does not necessarily increase. Option D, while often true (as gases can be produced), is not universally applicable; some reactions do not produce gas. Hence, the formation of a new substance is the definitive indicator of a chemical change.
An astronaut travels to the Moon, where the magnitude of the force of gravity is one-sixth the magnitude of the force of gravity on Earth. On the Moon, which of the following is true?
- A. The astronaut's mass is one-sixth of his mass on Earth.
- B. The astronaut's weight is one-sixth of his weight on Earth.
- C. The astronaut's mass is six times his mass on Earth.
- D. The astronaut's weight is six times his weight on Earth.
Correct Answer & Rationale
Correct Answer: B
An astronaut's mass remains constant regardless of location; therefore, option A is incorrect as mass on the Moon is the same as on Earth. Option C is also incorrect because mass does not change based on gravitational force. Option D misrepresents weight; weight is dependent on gravity, and since the Moon's gravity is one-sixth that of Earth's, the astronaut's weight is one-sixth, not six times. Thus, option B accurately reflects that the astronaut's weight on the Moon is one-sixth of his weight on Earth, aligning with the relationship between weight and gravitational force.
An astronaut's mass remains constant regardless of location; therefore, option A is incorrect as mass on the Moon is the same as on Earth. Option C is also incorrect because mass does not change based on gravitational force. Option D misrepresents weight; weight is dependent on gravity, and since the Moon's gravity is one-sixth that of Earth's, the astronaut's weight is one-sixth, not six times. Thus, option B accurately reflects that the astronaut's weight on the Moon is one-sixth of his weight on Earth, aligning with the relationship between weight and gravitational force.
Earth's diameter is approximately 12,700 kilometers. Which of the following layers is located approximately 6,000 kilometers beneath Earth's surface and is composed primarily of iron and nickel?
- A. The core
- B. The crust
- C. The lithosphere
- D. The mantle
Correct Answer & Rationale
Correct Answer: A
The core, located about 6,000 kilometers beneath Earth's surface, is primarily composed of iron and nickel, making it the densest layer of the planet. The crust, option B, is the outermost layer and is much shallower, averaging only about 30 kilometers thick. Option C, the lithosphere, includes the crust and the uppermost part of the mantle, but it does not reach anywhere near 6,000 kilometers deep. The mantle, option D, lies between the crust and the core, extending to about 2,900 kilometers down, but it is primarily composed of silicate minerals, not iron and nickel.
The core, located about 6,000 kilometers beneath Earth's surface, is primarily composed of iron and nickel, making it the densest layer of the planet. The crust, option B, is the outermost layer and is much shallower, averaging only about 30 kilometers thick. Option C, the lithosphere, includes the crust and the uppermost part of the mantle, but it does not reach anywhere near 6,000 kilometers deep. The mantle, option D, lies between the crust and the core, extending to about 2,900 kilometers down, but it is primarily composed of silicate minerals, not iron and nickel.