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Which of the following is an example of a chemical change?
- A. Dissolving sugar in water
- B. Boiling water
- C. Rusting iron
- D. Crushing ice
Correct Answer: C
Rationale: Rusting iron is an example of a chemical change because it involves a chemical reaction where iron reacts with oxygen in the presence of water to form iron oxide (rust). This reaction results in a change in the chemical composition of the iron, unlike dissolving sugar in water, boiling water, or crushing ice, which are physical changes. Dissolving sugar in water is a physical change as sugar molecules remain unchanged but disperse in water. Boiling water is also a physical change as water changes its state from liquid to gas due to heat. Crushing ice is a physical change as the solid ice changes its physical form without altering its chemical composition.
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Define the term 'velocity' in relation to motion.
- A. Speed in a specific direction
- B. Distance traveled in a given time
- C. Rate of change of position
- D. Acceleration due to gravity
Correct Answer: A
Rationale: Velocity is a vector quantity that describes the speed of an object along with its direction of motion. Unlike speed, which is a scalar quantity focusing solely on the magnitude of motion, velocity considers both speed and direction. Therefore, the best definition of velocity is 'speed in a specific direction.' Choice B, 'Distance traveled in a given time,' is incorrect as it defines speed rather than velocity. Choice C, 'Rate of change of position,' is more aligned with the definition of velocity but lacks the specificity of direction. Choice D, 'Acceleration due to gravity,' is unrelated to the definition of velocity and refers to a different concept in physics.
What happens during a physical change in matter?
- A. A new substance with different properties is formed
- B. The chemical composition of the substance changes
- C. The original substance can be recovered by physical means
- D. Energy is either released or absorbed
Correct Answer: C
Rationale: During a physical change in matter, the original substance undergoes a change in its physical state or appearance without any change in its chemical composition. This means that the original substance can be recovered by physical means, such as melting, freezing, boiling, or condensing. No new substance is formed (option A), the chemical composition remains the same (option B), and energy changes can occur but are not a defining characteristic of a physical change (option D). The ability to recover the original substance by physical means distinguishes physical changes from chemical changes.
In the process of cellular respiration, glucose is broken down to produce energy. What is the main waste product released?
- A. Water
- B. Carbon dioxide
- C. Oxygen
- D. Protein
Correct Answer: B
Rationale: During cellular respiration, glucose undergoes a series of reactions in the presence of oxygen to produce energy in the form of ATP. The main waste product released in this process is carbon dioxide, which is eliminated from the body through exhalation. While water is also produced as a byproduct of cellular respiration, carbon dioxide is considered the primary waste product. Oxygen is not a waste product but is actually consumed during cellular respiration to aid in breaking down glucose. Protein is essential for various cellular functions but is not a waste product of cellular respiration; instead, proteins are broken down into amino acids for cellular processes.
What is the shape of the DNA molecule?
- A. Linear
- B. Circular
- C. Double helix
- D. Straight chain
Correct Answer: C
Rationale: The correct answer is C: Double helix. The shape of the DNA molecule is a double helix, a structure first described by James Watson and Francis Crick in 1953. This shape consists of two strands twisted around each other in a spiral. The double helix structure allows DNA to be compactly stored within the cell nucleus and provides stability to the molecule. Options (A) Linear, (B) Circular, and (D) Straight chain are incorrect as they do not accurately represent the shape of the DNA molecule. DNA is not linear but rather forms a twisted double helix; it is not circular like a ring but has a spiral structure, and it is not a straight chain but a twisted ladder-like structure.
The process by which an organism adapts to its environment through inherited traits is known as
- A. Acclimatization
- B. Behavioral ecology
- C. Natural selection
- D. Niche partitioning
Correct Answer: C
Rationale: A) Acclimatization refers to the short-term physiological adjustments an individual organism makes in response to changes in its environment. This process is reversible and does not involve inherited traits.
B) Behavioral ecology is the study of how behavior contributes to an organism's survival and reproduction in its environment. While behavior can be influenced by natural selection, it is not the process by which an organism adapts through inherited traits.
C) Natural selection is the process by which organisms with advantageous traits for their environment are more likely to survive, reproduce, and pass on those traits to their offspring. Over time, this leads to the adaptation of populations to their environments.
D) Niche partitioning is the process by which species divide resources to reduce competition within an ecosystem. While this can influence the evolution of species, it is not the process by which an organism adapts through inherited traits.