Nokea
When is a solution considered saturated?
- A. More solute cannot be dissolved
- B. The solvent starts to evaporate
- C. The solution becomes cloudy
- D. It reaches a specific temperature
Correct Answer: A
Rationale: A solution is considered saturated when it has dissolved the maximum amount of solute that can be dissolved at a given temperature. At this point, adding more solute will not result in further dissolution, indicating that the solution is saturated. The other choices are incorrect because the solvent evaporating or the solution becoming cloudy are not definitive indicators of a saturated solution. Additionally, reaching a specific temperature does not determine saturation, as the solubility of a solute can vary with temperature. Therefore, the correct answer is that more solute cannot be dissolved in a saturated solution.
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Which term describes the resistance of a substance to being hammered into different shapes?
- A. Viscosity
- B. Ductility
- C. Malleability
- D. Conductivity
Correct Answer: C
Rationale: Malleability is the property that allows a substance to be hammered or rolled into thin sheets without breaking. It is the opposite of brittleness. Ductility refers to the ability of a material to be drawn into thin wires, not hammered into shapes. Viscosity is the measure of a fluid's resistance to flow, indicating how thick or sticky it is, not related to shaping by hammering. Conductivity refers to the ability of a material to conduct electricity or heat, not resistance to being hammered into different shapes.
Which of the following is NOT a source of genetic variation in a population?
- A. Mutations in genes
- B. Genetic drift (random fluctuations in allele frequencies)
- C. Gene flow (movement of genes between populations)
- D. Blending inheritance (traits of parents are averaged in offspring)
Correct Answer: D
Rationale: Rationale:
A) Mutations in genes: Mutations are changes in the DNA sequence that can introduce new alleles into a population, leading to genetic variation.
B) Genetic drift (random fluctuations in allele frequencies): Genetic drift refers to random changes in allele frequencies in a population, which can lead to genetic variation through chance events.
C) Gene flow (movement of genes between populations): Gene flow occurs when individuals move between populations, bringing new alleles with them and increasing genetic variation within populations.
D) Blending inheritance (traits of parents are averaged in offspring): Blending inheritance was a historical theory that suggested offspring inherit a blend of traits from their parents, leading to a reduction in genetic variation over time. However, this concept has been disproven by the understanding of Mendelian genetics, where traits are inherited independently and do not blend together.
Therefore, blending inheritance does not contribute
Which part of the neuron receives incoming signals from other neurons and conducts them toward the cell body?
- A. Axon
- B. Dendrite
- C. Synapse
- D. Myelin sheath
Correct Answer: B
Rationale: The dendrites are the part of the neuron that receive incoming signals from other neurons and conduct them toward the cell body. They play a crucial role in integrating signals received from other neurons. The dendrites are covered in synapses, which are the junctions where communication between neurons occurs. The axon, on the other hand, is responsible for transmitting signals away from the cell body. The synapse is the gap between neurons where neurotransmitters are released to facilitate communication. Lastly, the myelin sheath is a fatty layer that insulates and speeds up signal transmission along the axon, helping in the efficient conduction of nerve impulses.
What is the name of the strong acid produced by the stomach to help break down food?
- A. Hydrochloric acid
- B. Lactic acid
- C. Bile
- D. Fatty acid
Correct Answer: A
Rationale: The correct answer is A, hydrochloric acid. The stomach produces hydrochloric acid to aid in the digestion process by breaking down food, particularly proteins. This acid is crucial for the proper absorption of nutrients in the stomach. Lactic acid is produced in muscles during intense exercise, not in the stomach. Bile is produced by the liver to assist in digestion, primarily in the small intestine, not in the stomach. Fatty acids are molecules found in fats with different functions in the body, but they are not the primary acid produced by the stomach for digestion.
In nuclear physics, the term 'barn' is a unit commonly used to quantify:
- A. Energy
- B. Radioactivity
- C. Nuclear cross-section
- D. Half-life
Correct Answer: C
Rationale: In nuclear physics, the term 'barn' is a unit used to quantify nuclear cross-section. Nuclear cross-section is a measure of the probability of a nuclear reaction occurring when an atomic nucleus interacts with a particle or another nucleus. The barn is a unit of area equal to 10^-28 square meters; it is commonly used to describe the cross-sectional area of atomic nuclei for nuclear reactions. Choice A, 'Energy,' is incorrect because a barn is not a unit for measuring energy; it is a unit of area. Choice B, 'Radioactivity,' is incorrect as radioactivity is typically measured in units like becquerels. Choice D, 'Half-life,' is also incorrect as half-life is a measure of the time it takes for half of a substance to decay, not related to the concept of a barn as a unit of nuclear cross-section.