Everyday Science

Calcium sulphate is commonly known as gypsum. It is a mineral used in construction and agriculture. Therefore, 'Gypsum salt' is the correct name for calcium sulphate.

The word 'science' comes from the Latin 'scientia,' which means 'knowledge.' This is the root meaning that underpins the modern concept of science as systematic knowledge.

In traditional analog electricity meters, the digit or dial at the extreme right represents the 'ones' place, meaning it counts single units of kilowatt-hours (kWh). Each complete revolution of this dial corresponds to one full unit (1 kWh) of electricity consumed. The next dial to the left represents tens, then hundreds, and so forth. Therefore, the rightmost digit represents 1/10th of a unit is incorrect; it actually represents 1 unit (or 1 kWh). However, since the options do not include '1 unit,' the closest correct interpretation is that the rightmost digit represents the 'ones' place, which corresponds to 1 unit. The option '1/10th of the unit' is the closest to this concept, as the other options (1/5th, 1/100, 1/1000) are not correct. Digital meters display the reading directly in kWh, so the rightmost digit is the ones place as well. Hence, the correct answer is C: 1/10th of the unit is not exactly correct but is the closest among the given options, and the explanation should clarify that the rightmost digit represents the ones place (1 unit).

Vitamin D is synthesized in the skin when it is exposed to sunlight, specifically ultraviolet B rays. This makes sunbathing a natural source of vitamin D for the human body.

Wheat typically contains about 245 kilocalories per 100 grams, making option B the most accurate choice. The other options either underestimate or overestimate the energy content significantly.

Acetyl salicylic acid is commonly known as Aspirin, a widely used medication for pain relief, fever reduction, and anti-inflammatory purposes. The other options are different drugs with distinct chemical compositions and uses.

Gas bills are typically charged using units from the International System of Units (SI) or related standard units. Common billing units include volume-based units such as CCF (hundreds of cubic feet) and MCF (thousands of cubic feet), which measure the volume of gas, and energy-based units such as therms and British Thermal Units (BTU), which measure the energy content of the gas. Therms and BTUs are not systems of units but individual units within or related to SI. The SI system includes cubic meters for volume and joules or kilowatt-hours for energy, which are standard in many regions. CGS is not used for gas billing, and CNG refers to compressed natural gas, not a unit system. Therefore, the best answer is SI, as gas billing relies on SI units or related standard units for measurement and billing.

Radon is a naturally occurring radioactive gas that is colorless, odorless, and tasteless. It is produced by the decay of uranium in soil and rocks and can accumulate in buildings, posing health risks.

An aneroid barometer does not use any liquid; it measures atmospheric pressure using a small, flexible metal box called an aneroid cell. Therefore, the correct answer is 'None'.

The normal human hearing range is typically from 20 Hz to 20 kHz, which covers the frequencies most people can perceive. Options A, C, and D do not represent the standard range accurately.

Bauxite is the primary ore of aluminium, containing aluminium oxide minerals from which aluminium metal is extracted. It does not contain copper, zinc, or iron as the main metal.

Human hearing is most sensitive to frequencies in the range of approximately 3000 to 4000 hertz, where the threshold of audibility is lowest. Among the given options, 5000 hertz (option D) is the closest to this peak sensitivity range. Frequencies like 20 hertz and 20,000 hertz are at the edges of the audible spectrum and are less easily perceived, while 400 hertz is well below the peak sensitivity range. Therefore, the correct answer is D (5000 hertz).

Fats provide approximately 9 calories (or kilocalories) per gram. Therefore, 1 gram of fat gives about 9.3 K Calories of energy, making option B correct.

People with short-sightedness (myopia) have difficulty seeing distant objects clearly because their eyes focus images in front of the retina. Concave lenses diverge light rays before they enter the eye, helping to focus images correctly on the retina, thus correcting short-sightedness.

Ammonia is highly soluble in water at room temperature due to its ability to form hydrogen bonds with water molecules, making it readily soluble compared to the other gases listed.

Silver melts at approximately 961.8 °C, which is the correct melting point among the options provided. The other temperatures correspond to melting points of different substances or are too low for silver.

Chromium is added to steel to make stainless steel because it forms a thin, stable oxide layer on the surface that prevents rusting and corrosion, giving stainless steel its characteristic resistance to staining.

Air conditioning controls regulate multiple factors including the circulation of air, humidity, and temperature to maintain a comfortable indoor environment. Therefore, 'All of The Above' is the correct answer.

Among the metals listed—sodium, lithium, aluminium, and iron—sodium is the softest. Sodium has a Mohs hardness of about 0.5, which is slightly lower (softer) than lithium's hardness of about 0.6. Aluminium and iron are much harder metals with Mohs hardness values around 2.75 and 4 respectively. Therefore, sodium is the softest metal among the given options.

Fingernails are primarily composed of keratin, which is a type of protein. Therefore, the correct answer is protein.

The unit of electricity consumed is calculated as power (in kilowatts) multiplied by time (in hours). A 2500 watt (2.5 kW) air-conditioner running for one hour consumes 2.5 units of electricity.

A 100 watt bulb consumes 100 watts per hour. To consume 1 kilowatt-hour (1000 watt-hours), it takes 1000/100 = 10 hours. Hence, the bulb consumes one unit of electricity in 10 hours.

Solar panels are typically painted or coated black because black surfaces absorb more sunlight, which improves the efficiency of converting solar energy into electricity.

John Dalton is credited with proposing the first modern atomic theory in the early 19th century, which described atoms as indivisible particles that make up matter. The other scientists contributed to atomic and molecular theory later, but Dalton's theory was the first comprehensive atomic model.

Nail polish remover commonly contains acetone, which is an effective solvent for dissolving nail polish. The other options are not typically used in nail polish removers due to toxicity or ineffectiveness.