Which of the following best describes a chemical change?
- A. The melting of ice into water.
- B. The breaking of a piece of glass.
- C. The burning of wood in a fireplace.
- D. The bending of a metal wire.
Correct Answer & Rationale
Correct Answer: C
A chemical change involves a transformation that alters the substance's chemical structure. Option A describes a physical change, where ice melts into water without changing its chemical composition. Option B also represents a physical change; breaking glass does not alter the glass's chemical identity. Option D, bending a metal wire, is another physical change, as the metal's composition remains the same despite its shape being altered. In contrast, burning wood in a fireplace (Option C) results in new substances, such as ash and gases, indicating a chemical change has occurred.
A chemical change involves a transformation that alters the substance's chemical structure. Option A describes a physical change, where ice melts into water without changing its chemical composition. Option B also represents a physical change; breaking glass does not alter the glass's chemical identity. Option D, bending a metal wire, is another physical change, as the metal's composition remains the same despite its shape being altered. In contrast, burning wood in a fireplace (Option C) results in new substances, such as ash and gases, indicating a chemical change has occurred.
Other Related Questions
Which of the following was the dependent variable in this investigation?
- A. The wingspan
- B. The flight distance
- C. The stopwatch
- D. The tape measure
Correct Answer & Rationale
Correct Answer: B
In this investigation, the dependent variable is the outcome that is measured in response to changes in the independent variable. Flight distance (B) reflects how far something travels, which depends on the conditions set by the experiment. Wingspan (A) is an independent variable if it is being manipulated to see its effect on flight distance. The stopwatch (C) is a tool used to measure time and does not represent a variable in the experiment. Similarly, the tape measure (D) is an instrument for measuring distance, not a variable being tested. Thus, flight distance is the key outcome that reflects the effects of the experiment.
In this investigation, the dependent variable is the outcome that is measured in response to changes in the independent variable. Flight distance (B) reflects how far something travels, which depends on the conditions set by the experiment. Wingspan (A) is an independent variable if it is being manipulated to see its effect on flight distance. The stopwatch (C) is a tool used to measure time and does not represent a variable in the experiment. Similarly, the tape measure (D) is an instrument for measuring distance, not a variable being tested. Thus, flight distance is the key outcome that reflects the effects of the experiment.
The speed of light in empty space, that is, a vacuum, is 300,000 km/s. The speed of sound in empty space is:
- B. greater than 0 but less than 300,000 km/s
- C. 300,000 km/s
- D. greater than 300,000 km/s
Correct Answer & Rationale
Correct Answer: A
The speed of sound requires a medium, such as air or water, to propagate; it cannot travel through a vacuum. Therefore, the speed of sound in empty space is effectively zero. Option B suggests that the speed of sound is greater than 0 but less than 300,000 km/s, which is incorrect because sound cannot exist in a vacuum. Option C states it is 300,000 km/s, which misrepresents sound's nature, as this speed is specific to light. Option D claims it is greater than 300,000 km/s, which is impossible since sound cannot travel in a vacuum at all. Thus, the only valid conclusion is that the speed of sound in empty space is zero.
The speed of sound requires a medium, such as air or water, to propagate; it cannot travel through a vacuum. Therefore, the speed of sound in empty space is effectively zero. Option B suggests that the speed of sound is greater than 0 but less than 300,000 km/s, which is incorrect because sound cannot exist in a vacuum. Option C states it is 300,000 km/s, which misrepresents sound's nature, as this speed is specific to light. Option D claims it is greater than 300,000 km/s, which is impossible since sound cannot travel in a vacuum at all. Thus, the only valid conclusion is that the speed of sound in empty space is zero.
Which of the following is a statement that proposes a possible explanation for a phenomenon and can be tested through experimentation?
- A. An observation
- B. A variable
- C. An experiment
- D. A hypothesis
Correct Answer & Rationale
Correct Answer: D
A hypothesis is a statement that proposes a possible explanation for a phenomenon and can be tested through experimentation. It serves as a foundation for scientific inquiry. Option A, an observation, refers to data gathered through the senses and does not propose an explanation. Option B, a variable, is a factor that can change in an experiment but does not itself explain phenomena. Option C, an experiment, is a method used to test a hypothesis but is not a statement proposing an explanation. Thus, only a hypothesis encapsulates a testable explanation.
A hypothesis is a statement that proposes a possible explanation for a phenomenon and can be tested through experimentation. It serves as a foundation for scientific inquiry. Option A, an observation, refers to data gathered through the senses and does not propose an explanation. Option B, a variable, is a factor that can change in an experiment but does not itself explain phenomena. Option C, an experiment, is a method used to test a hypothesis but is not a statement proposing an explanation. Thus, only a hypothesis encapsulates a testable explanation.
Of the following, which has Earth completed when it makes one revolution around the Sun?
- A. One Earth year
- B. One Earth day
- C. One light year
- D. One lunar month
Correct Answer & Rationale
Correct Answer: A
When Earth completes one revolution around the Sun, it takes approximately 365.25 days, which defines one Earth year. Option B, one Earth day, represents the time it takes for Earth to rotate on its axis, not its orbit around the Sun. Option C, one light year, is a measure of distance that light travels in one year, not a measure of time related to Earth's orbit. Option D, one lunar month, refers to the time it takes for the Moon to orbit Earth, which is about 29.5 days, and is unrelated to Earth's revolution around the Sun.
When Earth completes one revolution around the Sun, it takes approximately 365.25 days, which defines one Earth year. Option B, one Earth day, represents the time it takes for Earth to rotate on its axis, not its orbit around the Sun. Option C, one light year, is a measure of distance that light travels in one year, not a measure of time related to Earth's orbit. Option D, one lunar month, refers to the time it takes for the Moon to orbit Earth, which is about 29.5 days, and is unrelated to Earth's revolution around the Sun.