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Which of the following is an example of a decomposition reaction?
- A. 2H2 + O2 → 2H2O
- B. CaCO3 → CaO + CO2
- C. 2Na + Cl2 → 2NaCl
- D. N2 + 3H2 → 2NH3
Correct Answer: B
Rationale: A decomposition reaction involves a single compound breaking down into two or more simpler substances. In option B, CaCO3 breaks down into CaO and CO2, making it an example of a decomposition reaction. Options A, C, and D involve different types of chemical reactions such as synthesis, combination, and combustion, respectively. Option A represents a synthesis reaction, where two elements combine to form a compound. Option C demonstrates a combination reaction, where two elements combine to form a compound. Option D is an example of a synthesis reaction, where two reactants combine to form a single compound. It is important to recognize the specific characteristics of each type of chemical reaction to identify the correct example of decomposition reaction, where a compound breaks down into simpler products.
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An object is moving in a circle at constant speed. Is there a net force acting on it?
- A. Yes, always
- B. No, never
- C. Only if its speed is changing
- D. Only if its direction is changing
Correct Answer: D
Rationale: When an object is moving in a circle at a constant speed, there is a net force acting on it. This net force is directed towards the center of the circle and is responsible for continuously changing the direction of the object's velocity, even though the speed remains constant. Therefore, the correct answer is D because the net force is required to change the direction of the object's motion in a circular path. Choices A, B, and C are incorrect because the presence of a net force is necessary to continuously change the object's direction as it moves in a circular path, irrespective of changes in speed.
What is the largest bone in the human body?
- A. Femur (thigh bone)
- B. Tibia (shin bone)
- C. Humerus (upper arm bone)
- D. Scapula (shoulder blade)
Correct Answer: A
Rationale: The femur, also known as the thigh bone, holds the title of the largest bone in the human body. Situated in the upper leg, the femur plays a vital role in supporting the body's weight and enabling movement. While the tibia (shin bone), humerus (upper arm bone), and scapula (shoulder blade) are all essential bones, none of them match the femur in terms of size and importance. The tibia, humerus, and scapula are comparatively smaller bones with specific functions in their respective areas of the body, but they do not surpass the femur in size or significance.
Skeletal muscles are attached to bones by tough connective tissues called
- A. Ligaments
- B. Tendons
- C. Cartilage
- D. Fascia
Correct Answer: B
Rationale: Skeletal muscles are attached to bones by tough connective tissues called tendons. Tendons are strong, fibrous cords that connect muscles to bones, allowing for movement and stability in the body. Ligaments (option A) connect bones to other bones, not muscles to bones. Cartilage (option C) is firm and flexible connective tissue found in various parts of the body, but it does not attach muscles to bones. Fascia (option D) is a connective tissue that surrounds muscles, providing support and protection, but it does not directly attach muscles to bones.
What is the recommended daily fiber intake for adults?
- A. 10 grams
- B. 25 grams
- C. 35 grams
- D. 50 grams
Correct Answer: B
Rationale: The recommended daily fiber intake for adults is around 25 grams for women and 38 grams for men. Fiber is essential for maintaining a healthy digestive system, preventing constipation, and reducing the risk of chronic diseases such as heart disease and diabetes. Consuming an adequate amount of fiber can also help with weight management and promote overall well-being. Option B is the correct answer based on the recommended daily intake guidelines for adults. Choices A, C, and D are incorrect because they do not align with the established guidelines for fiber intake in adults. 10 grams (choice A) is too low, 35 grams (choice C) is higher than the general recommendation, and 50 grams (choice D) is significantly above the recommended intake, which may lead to digestive issues in some individuals.
What is the term for the gradual loss of topsoil due to wind or water erosion?
- A. Desertification
- B. Leaching
- C. Salinization
- D. Acidification
Correct Answer: A
Rationale: A) Desertification is the correct term for the gradual loss of topsoil due to wind or water erosion. It refers to the process by which fertile land becomes desert, usually due to factors like drought, deforestation, or inappropriate agriculture practices. This process can lead to the degradation of land and contribute to the expansion of deserts. B) Leaching is the process in which minerals are washed out of the soil by water moving downwards through it. This is different from the loss of topsoil due to erosion. C) Salinization occurs when salt accumulates in the soil, typically as a result of irrigation in arid regions. While salinization affects soil quality, it is not specifically related to the gradual loss of topsoil due to erosion. D) Acidification refers to the decrease in soil pH, often caused by factors like acid rain or the use of acidic fertilizers. This process is distinct from the gradual loss of topsoil due to erosion.