Nokea
Which of the following is an example of a chemical change?
- A. Dissolving sugar in water
- B. Boiling water
- C. Rusting iron
- D. Crushing ice
Correct Answer: C
Rationale: Rusting iron is an example of a chemical change because it involves a chemical reaction where iron reacts with oxygen in the presence of water to form iron oxide (rust). This reaction results in a change in the chemical composition of the iron, unlike dissolving sugar in water, boiling water, or crushing ice, which are physical changes. Dissolving sugar in water is a physical change as sugar molecules remain unchanged but disperse in water. Boiling water is also a physical change as water changes its state from liquid to gas due to heat. Crushing ice is a physical change as the solid ice changes its physical form without altering its chemical composition.
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What happens during a physical change in matter?
- A. A new substance with different properties is formed
- B. The chemical composition of the substance changes
- C. The original substance can be recovered by physical means
- D. Energy is either released or absorbed
Correct Answer: C
Rationale: During a physical change in matter, the original substance undergoes a change in its physical state or appearance without any change in its chemical composition. This means that the original substance can be recovered by physical means, such as melting, freezing, boiling, or condensing. No new substance is formed (option A), the chemical composition remains the same (option B), and energy changes can occur but are not a defining characteristic of a physical change (option D). The ability to recover the original substance by physical means distinguishes physical changes from chemical changes.
Which gland, often referred to as the 'master gland' of the endocrine system and located at the base of the brain, secretes various hormones that control other glands?
- A. Thyroid gland
- B. Pituitary gland
- C. Adrenal gland
- D. Pancreas
Correct Answer: B
Rationale: The pituitary gland is correctly known as the 'master gland' of the endocrine system. It is situated at the base of the brain and plays a crucial role in secreting a variety of hormones that regulate the functions of other endocrine glands in the body. These hormones control growth, metabolism, reproduction, and various other essential bodily functions. The other choices, thyroid gland, adrenal gland, and pancreas, are incorrect as they do not serve as the 'master gland' of the endocrine system nor are located at the base of the brain like the pituitary gland.
Which of the following factors would increase the solubility of a gas in a liquid?
- A. Decreasing temperature
- B. Increasing pressure
- C. Decreasing surface area
- D. Increasing particle size
Correct Answer: B
Rationale: The correct answer is increasing pressure. According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. Therefore, increasing pressure would force more gas molecules into the liquid, leading to an increase in solubility. Conversely, decreasing temperature, decreasing surface area, and increasing particle size would not directly impact the solubility of a gas in a liquid. Decreasing temperature typically decreases solubility as gases are less soluble at lower temperatures. Decreasing surface area and increasing particle size are related to surface area and not the pressure above the liquid, thus not affecting solubility as pressure does.
What is the relationship between the speed of a wave, its frequency, and wavelength in a given medium?
- A. Speed = Frequency Wavelength
- B. Speed = Frequency · Wavelength
- C. Speed = Frequency + Wavelength
- D. Speed = Frequency - Wavelength
Correct Answer: A
Rationale: The speed of a wave in a given medium is determined by the product of its frequency and wavelength. This relationship is described by the formula: Speed = Frequency Wavelength. When a wave travels through a medium, the speed at which it propagates is directly proportional to both its frequency and wavelength. Therefore, to calculate the speed of the wave, you multiply the frequency of the wave by its wavelength. Choices B, C, and D are incorrect because speed is not determined by division, addition, or subtraction of frequency and wavelength; instead, it is determined by their multiplication in the given medium.
What causes dandruff?
- A. Excessive sebum production (This can contribute to oily dandruff)
- B. Bacterial infection (This can cause scalp folliculitis, not dandruff)
- C. Overgrowth of a specific type of fungus on the scalp
- D. Lack of proper skin hydration
Correct Answer: C
Rationale: Dandruff is primarily caused by an overgrowth of a specific type of fungus called Malassezia on the scalp. This fungus feeds on the natural oils produced by the hair follicles, leading to irritation and flaking of the scalp skin. Choice A is incorrect because excessive sebum production can contribute to oily dandruff, but it is not the primary cause of dandruff. Choice B is incorrect as bacterial infection primarily causes scalp folliculitis, not dandruff. Choice D is incorrect as dandruff is not primarily caused by a lack of proper skin hydration.