Nokea
What property of matter explains why ice floats on water?
- A. Viscosity
- B. Density
- C. Buoyancy
- D. Surface tension
Correct Answer: C
Rationale: The correct answer is C, buoyancy. Ice floats on water due to buoyancy, a property of matter. When water freezes into ice, it becomes less dense than liquid water, causing it to float. This phenomenon occurs because the molecules in ice are more spread out compared to liquid water, resulting in ice being less dense and able to float on the surface.
Choice A, viscosity, is incorrect because viscosity refers to a fluid's resistance to flow, not its ability to float.
Choice B, density, is incorrect because while ice being less dense than water is the reason it floats, this choice does not explain the specific property that causes this phenomenon.
Choice D, surface tension, is incorrect as it pertains to the cohesive forces between molecules at the surface of a liquid, not the reason why ice floats on water.
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What is the difference between a prokaryotic cell and a eukaryotic cell?
- A. Prokaryotic cells have a nucleus, while eukaryotic cells do not
- B. Eukaryotic cells have a nucleus, while prokaryotic cells do not.
- C. Prokaryotic cells have membrane-bound organelles, while eukaryotic cells do not.
- D. Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not.
Correct Answer: B
Rationale: - Prokaryotic cells are simpler and do not have a true nucleus. Their genetic material is located in the nucleoid region, which is not enclosed by a membrane.
- Eukaryotic cells are more complex and have a true nucleus that houses the genetic material, enclosed within a nuclear membrane.
- Both prokaryotic and eukaryotic cells have organelles, but eukaryotic cells have membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus, while prokaryotic cells lack these membrane-bound organelles.
Rusting of iron is an example of
- A. Endothermic reaction
- B. Exothermic reaction
- C. Single displacement reaction
- D. Photochemical reaction
Correct Answer: A
Rationale: The rusting of iron is an endothermic reaction. This means that it absorbs heat from its surroundings to occur. Rusting involves the slow oxidation of iron in the presence of oxygen and water. As energy is absorbed during this process, it is classified as an endothermic reaction. Choice B, an exothermic reaction, releases heat instead of absorbing it, which is not the case in rusting. Choices C and D are unrelated to the process of rusting and do not involve the absorption of heat from the surroundings.
What is the main function of calcitonin, a hormone produced by the thyroid gland?
- A. Stimulate metabolism and heat production
- B. Increase calcium absorption from the intestines
- C. Enhance bone growth and development
- D. Lower blood calcium levels
Correct Answer: D
Rationale: Calcitonin is a hormone produced by the thyroid gland that primarily functions to lower blood calcium levels. It achieves this by inhibiting bone breakdown and promoting calcium excretion by the kidneys. Therefore, the correct answer is D as it reflects the main role of calcitonin in calcium homeostasis. Choices A, B, and C are incorrect as they do not align with the primary function of calcitonin. Calcitonin does not stimulate metabolism and heat production (Choice A), increase calcium absorption from the intestines (Choice B), or enhance bone growth and development (Choice C).
What pigment is responsible for the yellow color of bananas?
- A. Potassium
- B. Calcium
- C. Phosphorus
- D. Carotene
Correct Answer: D
Rationale: Carotene is the pigment responsible for the yellow color of bananas. It belongs to a group of plant pigments called carotenoids, which are responsible for giving fruits and vegetables their vibrant colors, including the yellow hue of bananas. Potassium, calcium, and phosphorus are essential minerals found in bananas but are not responsible for their yellow color.
What is the term for a genetic disorder caused by a mutation on the X chromosome?
- A. Autosomal dominant disorder
- B. Autosomal recessive disorder
- C. Sex-linked recessive disorder
- D. Sex-linked dominant disorder
Correct Answer: C
Rationale: A genetic disorder caused by a mutation on the X chromosome is termed a sex-linked recessive disorder (Option C). This type of disorder is more commonly seen in males due to their single X chromosome, making them more vulnerable to X-linked mutations. Females have two X chromosomes, providing a protective effect against X-linked disorders.\n- Autosomal dominant disorders (Option A) result from a mutation in one copy of a gene on non-sex chromosomes (autosomes) and are not specifically related to the X chromosome.\n- Autosomal recessive disorders (Option B) occur due to mutations in both copies of a gene on autosomes, not on the X chromosome.\n- Sex-linked dominant disorders (Option D) are rare and lead to more severe symptoms in males as they only require one copy of the mutated gene on the X chromosome to express the disorder. However, this is not the term for a genetic disorder caused by an X chromosome mutation.