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A student conducts an experiment where they dissolve 1 g each of several substances in 50 mL of water. They have 12 identical plastic cups of water and place 1 g of salt into three of the cups, 1 g of sugar into three of the cups, and 1 g of baking soda into three of the cups. The three remaining cups contain only water. All the cups are put in a freezer, and the temperature of the solution in each cup is recorded every 15 minutes for 4 hours. What question is the student most likely investigating?

  • A. What effect do different concentrations of solute have on the freezing point of water?
  • B. How does the volume of water affect the rate at which it cools?
  • C. What effect does cooling have on the solubility of different solutes?
  • D. How is the cooling rate of water affected by different solutes?
Correct Answer: A

Rationale: The student is most likely investigating the effect of different concentrations of solutes (salt, sugar, baking soda) on the freezing point of water. By monitoring the temperature changes during freezing, the student can observe how each solute affects the freezing point. This experiment helps understand the concept of colligative properties, where the presence of solutes lowers the freezing point of a solvent like water. Therefore, the correct answer is A: 'What effect do different concentrations of solute have on the freezing point of water?'

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Through which of the following transport mechanisms do water molecules enter cells?

  • A. Facilitated diffusion
  • B. Electrochemical gradients
  • C. Gated channels
  • D. Proton pumps
Correct Answer: A

Rationale: Water molecules enter cells through facilitated diffusion. Facilitated diffusion is the passive movement of molecules across a cell membrane with the help of specific transport proteins. In the case of water, it moves through specialized channels called aquaporins using this mechanism, allowing it to cross the membrane more efficiently than by simple diffusion. While electrochemical gradients, gated channels, and proton pumps play roles in transporting other substances and ions, they are not directly involved in the transport of water molecules into cells.

A student makes a solution that simulates stomach acid. Which of the following would be true of this solution, compared to distilled water?

  • A. It has a higher pH.
  • B. It has more hydrogen ions.
  • C. It contains more hydroxyl ions.
  • D. It has more hydroxyl ions.
Correct Answer: B

Rationale: The correct answer is B. A solution that simulates stomach acid is acidic, which means it has a higher concentration of hydrogen ions compared to distilled water, which is neutral. Stomach acid is characterized by its high hydrogen ion concentration, which is responsible for its acidic nature. Hydroxyl ions are associated with bases, not acids, so options C and D are incorrect. Option A is incorrect as well because stomach acid would have a lower pH compared to distilled water due to its high acidity.

Which of the following are the major parts of the nervous system?

  • A. PNS and Somatic Nervous System
  • B. Autonomic Nervous System and CNS
  • C. PNS and CNS
  • D. Autonomic Nervous System and Somatic Nervous System
Correct Answer: C

Rationale: The nervous system comprises two major parts: the peripheral nervous system (PNS) and the central nervous system (CNS). The PNS includes nerves outside the brain and spinal cord, while the CNS consists of the brain and spinal cord. Choice C (PNS and CNS) correctly identifies the primary divisions of the nervous system, encompassing both the peripheral and central components. Therefore, the correct answer is C.

In a phase diagram, what term is used for a substance held at a temperature and pressure where solid, liquid, and gaseous states of a substance exist simultaneously?

  • A. critical temperature
  • B. triple point
  • C. absolute zero
  • D. critical point
Correct Answer: B

Rationale: The point described in the question is called the triple point. At the triple point, all three phases of a substance (solid, liquid, and gas) coexist in equilibrium. The critical temperature is the highest temperature at which a distinct liquid phase can form, while absolute zero is the lowest possible temperature. The critical point is the point on a phase diagram that represents the highest temperature and pressure at which a distinct liquid and gas phase can coexist. Therefore, the correct answer is the triple point, where all three phases coexist.

Which of the following cell types produce and release antibodies?

  • A. Helper T cells
  • B. Cytotoxic T cells
  • C. Plasma B cells
  • D. Natural Killer cells
Correct Answer: C

Rationale: Plasma B cells are specialized cells that are responsible for producing and releasing antibodies. These antibodies play a vital role in the immune response by recognizing and neutralizing harmful pathogens like bacteria and viruses. Helper T cells aid in activating B cells and other immune cells, cytotoxic T cells are involved in eliminating infected or abnormal cells, and natural killer cells are part of the innate immune system, targeting virus-infected and tumor cells.

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