Nokea
To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, which of the following laboratory tools will a student need?
- A. Graduated cylinder, water, weighing balance
- B. Weighing balance, Bunsen burner, metric ruler
- C. Graduated cylinder, spectrophotometer, water
- D. Graduated beaker, metric ruler, water
Correct Answer: A
Rationale: To accurately measure the density of irregular solids made of various materials, a student needs specific laboratory tools. Firstly, a graduated cylinder is required to measure the volume of the irregular solids using the water displacement method, which allows for precise volume determination. Secondly, a weighing balance is necessary to measure the mass of the irregular solids accurately. Density is calculated by dividing the mass by the volume, hence the need for both mass and volume measurements. Therefore, the essential tools for this task are a combination of a graduated cylinder, water, and weighing balance (Choice A). These tools together provide the necessary measurements for calculating the density of the irregular solids accurately.
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An individual suffers blunt trauma to the thoracic cavity. Which of the following organs is at greatest risk from this injury?
- A. Heart and lungs
- B. Liver and stomach
- C. Brain and spinal cord
- D. Large and small intestines
Correct Answer: A
Rationale: Blunt trauma to the thoracic cavity poses the greatest risk to the heart and lungs. These organs are located within the chest cavity and are highly susceptible to damage from the impact of the trauma. Injuries to the heart and lungs can be severe, leading to life-threatening complications if not promptly addressed. Therefore, in cases of blunt trauma to the thoracic cavity, immediate medical evaluation is essential to identify and manage potential injuries to these critical organs.
What distinguishes endocrine and exocrine glands from one another?
- A. The biochemistry of their secretions
- B. The presence or absence of ducts
- C. The presence or absence of nerve innervation
- D. The effect their secretions have on the target cell
Correct Answer: B
Rationale: The correct answer is B. The presence or absence of ducts is the key factor that distinguishes endocrine and exocrine glands. Endocrine glands secrete hormones directly into the bloodstream without ducts, while exocrine glands secrete substances through ducts to the external environment or onto a surface. Choice A is incorrect because both types of glands can have different biochemistries in their secretions. Choice C is incorrect because both types of glands can receive nerve innervation. Choice D is incorrect as it does not differentiate between endocrine and exocrine glands based on the effect of their secretions on target cells.
What action would result in an increase in the rate of a chemical reaction?
- A. Adding more of the reactants
- B. Decreasing the temperature of the reactants
- C. Using a mortar and pestle to grind a solid reactant to a powder
- D. Sealing the reaction in an airtight container
Correct Answer: C
Rationale: Grinding a solid reactant to a powder increases the surface area exposed to other reactants, leading to more frequent collisions and a faster reaction rate. This process enhances the chances of successful collisions, hence accelerating the reaction. The other options do not directly impact the rate of a chemical reaction in the same manner. Adding more of the reactants provides more reactant particles to collide, promoting a higher reaction rate. Decreasing the temperature of the reactants generally slows down reactions by reducing the kinetic energy of the particles. Sealing the reaction in an airtight container may affect the equilibrium but not necessarily the reaction rate.
Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?
- A. Sebum
- B. Water
- C. Urea
- D. Lysozymes
Correct Answer: C
Rationale: Urea is the correct answer. Sweat glands excrete urea in response to the breakdown of proteins and the formation of ammonia. Urea is a waste product resulting from the breakdown of proteins in the liver and is excreted in urine as well as through sweat. Sebum is an oily substance produced by the skin's sebaceous glands, water is excreted by various means but is not specifically a result of protein breakdown, and lysozymes are enzymes that help protect the body against bacterial infections.
Lithium has an atomic number of 3 and a mass number of 7. What is the number of protons in a lithium atom?
- A. 7
- B. 4
- C. 12
- D. 3
Correct Answer: D
Rationale: The number of protons in an atom is equal to its atomic number. In this case, lithium has an atomic number of 3, so it contains 3 protons. The mass number (7) includes both protons and neutrons, with the difference between the mass number and atomic number representing the number of neutrons. Therefore, the correct answer is 3 protons in a lithium atom.