Nokea
What is the process of combining two or more substances to form a heterogeneous mixture called?
- A. Dissolving
- B. Diluting
- C. Mixing
- D. Reacting
Correct Answer: C
Rationale: The correct answer is 'Mixing.' When substances are combined, a heterogeneous mixture is formed where the components are physically distinguishable. 'Dissolving' (Choice A) is the process of a solute becoming uniformly dispersed in a solvent to form a solution, not a heterogeneous mixture. 'Diluting' (Choice B) refers to reducing the concentration of a solute in a solution. 'Reacting' (Choice D) involves a chemical change where substances interact to form new products, rather than just physically mixing to form a heterogeneous mixture.
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Why is the electrical conductivity of a strong acid solution higher than that of a weak acid solution?
- A. Strong acids are more concentrated.
- B. Strong acids release more hydrogen ions.
- C. Weak acids are better at dissolving salts.
- D. Strong acids have a lower pH.
Correct Answer: B
Rationale: The correct answer is B because strong acids release more hydrogen ions compared to weak acids. This higher concentration of ions in the solution leads to a higher electrical conductivity. Strong acids ionize completely in solution, producing a higher concentration of ions that can conduct electricity, whereas weak acids only partially ionize, resulting in a lower concentration of ions and lower electrical conductivity. Choice A is incorrect because the concentration of the acid does not directly determine its electrical conductivity. Choice C is incorrect as the ability to dissolve salts is not directly related to electrical conductivity. Choice D is incorrect because the pH of the solution, although related to acidity, does not directly determine the electrical conductivity.
Which of the following is a risk factor for developing kidney stones?
- A. Consuming a diet rich in fruits and vegetables
- B. Maintaining adequate hydration with water
- C. Having a family history of kidney stones
- D. Regularly engaging in moderate exercise
Correct Answer: C
Rationale: Having a family history of kidney stones is a risk factor for developing kidney stones. Genetic predisposition can increase the likelihood of developing kidney stones due to inherited traits that affect the body's ability to process and excrete certain substances. Consuming a diet rich in fruits and vegetables (option A) and maintaining adequate hydration with water (option B) are actually recommended strategies to help prevent kidney stones by promoting overall kidney health. Regularly engaging in moderate exercise (option D) can also be beneficial for kidney health by promoting circulation and overall well-being. Therefore, options A, B, and D are not risk factors but rather beneficial for kidney health.
Which of the following best describes a chemical change?
- A. Melting ice to form water
- B. Dissolving sugar in water
- C. Burning wood to produce ash
- D. Crushing a can to reduce its size
Correct Answer: C
Rationale: A chemical change involves a chemical reaction where new substances are formed. Burning wood to produce ash is an example of a chemical change because the wood undergoes a chemical reaction to form a new substance (ash). In this process, the chemical composition of wood changes to produce ash, which is a new substance. On the other hand, melting ice to form water, dissolving sugar in water, and crushing a can to reduce its size are examples of physical changes. In these instances, the substances may change their physical state or appearance but do not undergo a chemical reaction to form new substances. Therefore, choice C is the correct answer as it represents a chemical change, while choices A, B, and D represent physical changes.
Which of the following is NOT a function of the muscular system?
- A. Movement
- B. Maintaining posture
- C. Generating heat
- D. Regulating blood sugar levels
Correct Answer: D
Rationale: The muscular system is responsible for movement, maintaining posture, and generating heat. Regulating blood sugar levels is not a function of the muscular system. This function is primarily carried out by the endocrine system, specifically the pancreas and its production of insulin and glucagon. Choices A, B, and C are all correct functions of the muscular system as they involve the contraction and relaxation of muscles to produce movement, support the body's structure, and generate heat as a byproduct of muscle activity.
What phenomenon occurs when a wave encounters a change in medium causing a change in its speed and direction?
- A. Refraction
- B. Reflection
- C. Diffraction
- D. Interference
Correct Answer: A
Rationale: Refraction is the phenomenon that occurs when a wave encounters a change in medium, causing a change in its speed and direction. This change in speed and direction is due to the wave bending as it passes from one medium to another with a different density. It is essential to understand refraction as it plays a crucial role in various phenomena, such as the bending of light in lenses, the formation of rainbows, and the way seismic waves travel through the Earth's layers. Reflection, while also a wave phenomenon, involves the bouncing back of a wave when it encounters a boundary. Diffraction refers to the bending of waves around obstacles or through openings, and interference involves the combination of two or more waves to form a new wave pattern.