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Optics
The speed of light in vacuum is about:
The speed of light in vacuum is approximately 300 million meters per second (more precisely about 299,792,458 meters per second). This is a fundamental physical constant used in many scientific calculations.
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Thermometry
The most suitable thermometer for measuring the boiling point of water is:
A mercury thermometer is most suitable for measuring the boiling point of water because mercury has a high boiling point (357°C) and does not evaporate easily at 100°C, providing accurate and stable readings. Alcohol thermometers are less suitable due to alcohol's lower boiling point, and bimetallic thermometers are not typically used for precise temperature measurements like boiling point.
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Solar System Age
The age of the Solar System is:
The age of the Solar System is widely accepted by scientists to be about 4.5 billion years, based on radiometric dating of meteorites and lunar samples.
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Ocean Chemistry
The most abundant elements in seawater are:
The most abundant elements in seawater are sodium and chloride, which combine to form sodium chloride (common salt). These ions are the primary contributors to seawater's salinity.
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Sound
The speed of sound in dry air at 20°C is about:
The speed of sound in dry air at 20°C is approximately 330 meters per second, which is a well-established physical fact.
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Rocks and Minerals
Which rocks are formed by the alteration of pre-existing rocks by great heat or pressure?
Metamorphic rocks are formed when pre-existing rocks are subjected to great heat and pressure, causing physical and chemical changes without melting. This process alters the original rock into a new type, which is why option C is correct.
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Rocks and Minerals
There are three types of rocks. Into which category does limestone fall?
Limestone is a sedimentary rock formed primarily from calcium carbonate deposits, often from marine organisms. It does not belong to igneous or 'hard' rock categories, making 'Sedimentary' the correct classification.
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Colors
What are the primary colours?
The primary colors in traditional color theory for pigments are red, yellow, and blue. These colors cannot be created by mixing other colors and are used to mix all other colors.
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Biosensors
A biosensor is used to measure:
A biosensor is a device that uses biological molecules to detect specific substances. One of the most common applications is measuring blood glucose levels in diabetic patients, making option A correct.
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Salinity
The salinity of seawater is determined by the amount of common salt (Sodium Chloride) in a given amount of seawater. Which of the following amounts best represents the typical quantity of common salt in about 1 liter (or 1 kilogram) of seawater?
The salinity of seawater is typically about 3.5%, meaning there are approximately 35 grams of dissolved salts per kilogram (or liter) of seawater. Sodium chloride (common salt) is the major component but constitutes roughly 30 grams per liter, not 1 gram or 10 grams. The question as stated lacks clarity on the volume or mass of seawater considered, and none of the options A (1 gram), B (10 grams), or C (1 kg) correctly represent the typical amount of common salt in a standard amount of seawater. Therefore, the correct answer is D (None of these).