Nursing Elites

1. What is the difference between a pure substance and a mixture?

• A. Pure substances have a fixed composition, mixtures don't.
• B. Mixtures have a fixed composition, pure substances don't.
• C. Pure substances can be in any state, mixtures are not always solids.
• D. Pure substances are always elements, mixtures are always compounds.

Correct answer: A

Rationale: Pure substances have a definite and constant composition, meaning they are made up of only one type of atom or molecule with fixed proportions. This composition does not vary. On the other hand, mixtures are composed of two or more substances physically combined. The components of a mixture can be present in varying proportions, leading to a variable composition. Choice A is correct as it accurately distinguishes between pure substances and mixtures based on the fixed composition of pure substances and the variable composition of mixtures. Choice B is incorrect because mixtures, not pure substances, have variable compositions. Choice C is incorrect as both pure substances and mixtures can exist in different states. Choice D is incorrect because pure substances can be compounds as well, not exclusively elements, and mixtures can contain elements and compounds.

2. 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.

3. Not all cells in the pancreas secrete insulin because of the hormone somatostatin, which inhibits the release of insulin by all cells. What type of intercellular chemical signal does this illustrate?

• A. Autocrine
• B. Neuromodulator
• C. Paracrine
• D. Pheromone

Correct answer: C

Rationale: The correct answer is C: Paracrine. Somatostatin acts in a paracrine manner by inhibiting the release of insulin from nearby cells within the pancreas. Paracrine signaling involves the secretion of signals that act on neighboring cells, as seen in this scenario where somatostatin affects nearby pancreatic cells without entering the bloodstream or affecting distant cells. Autocrine signaling involves cells responding to substances they themselves release, which is not the case here. Neuromodulators are chemicals that modulate the activity of neurons, not directly related to this scenario. Pheromones are chemicals released into the environment to communicate with individuals of the same species, not relevant to the signaling within the pancreas.

4. Which of the following properties is characteristic of water?

• A. Water has a neutral pH.
• B. Water has a low specific heat capacity.
• C. Water has polar covalent bonds.
• D. Water can dissolve almost any solid, liquid, or gas.

Correct answer: D

Rationale: The correct answer is D because water's polarity enables it to dissolve a wide variety of substances, making it a versatile solvent. This property is due to water's ability to form hydrogen bonds with other molecules, allowing it to break them apart and surround the solute particles, facilitating dissolution. Choices A, B, and C are incorrect as water having a neutral pH, a high specific heat capacity, and polar covalent bonds are also true properties of water. However, the most relevant property related to its versatility as a solvent is its dissolving capability.

5. What property of a wave remains unchanged when it passes from one medium to another with the same speed?

• A. Frequency
• B. Wavelength
• C. Amplitude
• D. Speed

Correct answer: A

Rationale: When a wave passes from one medium to another with the same speed, its frequency remains unchanged. Frequency is a characteristic of the source of the wave and does not depend on the medium through which the wave is traveling. Wavelength and speed of the wave can change when passing from one medium to another, but frequency remains constant. This is because the frequency of a wave is determined by the source that produces it, and as long as the speed remains constant, the frequency will not be altered. Amplitude, on the other hand, can change based on factors like energy loss or gain, but it is not a property that remains constant when a wave moves between different mediums with the same speed. Speed, although important for the wave's propagation, is not the property that remains unchanged when the wave transitions between mediums with the same speed. Therefore, the correct answer is frequency.

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