[DAY 47] 60 DAY RAPID REVISION (RaRe) SERIES for UPSC Prelims 2025 – SCIENCE & TECHNOLOGY, CURRENT AFFAIRS & CSAT TEST SERIES!

Solution (b)

Explanation:

• • Aluminium is highly malleable material and thus can be made into very thin sheets or foils that can be later used for keeping food items.  Hence Statement 1 is correct.
  • Aluminium as such does not react with the food items kept in the aluminium foil and hence is used for storing food in it. Hence Statement 2 is correct.

• Yes, aluminium is very ductile which means it can be made into very thin wires. However, it is not the reason that aluminium is used for storing food. Hence Statement 3 is incorrect.

• Aluminium foil does keep the food warm for longer by trapping the hotter air inside, which then serves as an insulator, and by preventing heat loss due to radiation. Aluminium is a good conductor of heat. Hence Statement 4 is incorrect.

Solution (c)

Explanation: 

• • Certain substances are used to test whether a substance is acidic or basic. These substances are known as indicators. The indicators change their colour when added to a solution containing an acidic or a basic substance. Turmeric, litmus, china rose petals, Petunia are some of the naturally occurring indicators.
  • Litmus is a natural indicator extracted from lichens. It has a mauve (purple) colour in distilled water. When added to an acidic solution, Litmus turns red and when added to a basic solution, it turns blue. Hence Option 1 is correct.
  • Turmeric is a natural acid-base indicator. It helps us identify the nature of any given substance by itself undergoing a colour change. It turns yellow in acidic medium and changes its colour to red in basic medium. Hence Option 2 is correct.

• China rose is a naturally occurring indicator. China rose indicator turns from light pink to Magenta (deep pink) colour when mixed with acidic substances. On the other hand, a basic substance turns China rose indicator from light pink to Green in colour. Hence Option 3 is correct.

Solution (d)

Explanation:

Sublimation is the phenomenon of conversion of a substance from the solid to the gaseous state without becoming liquid. For instance, the vaporization of frozen carbon dioxide which is also called as dry ice at ordinary atmospheric pressure and temperature is the example of Sublimation process. This phenomenon only results in the changes in the physical state not chemical. Disappearance of Naphthalene balls is also an example of Sublimation process. It is because material is directly converted from solid state into the gaseous state. Hence option d is correct

Solution (a)

Explanation:

• When light is incident on a metal, electrons can be ejected from the surface of the metal in a phenomenon known as the photoelectric effect. This process is also often referred to as photoemission, and the electrons that are ejected from the metal are called photoelectrons. Hence Statement 1 is correct.

The number of electrons ejected in a photoelectric effect is proportional to the intensity of light. Hence Statement 2 is incorrect.

Solution (b)

Explanation:

• As altitude increases, the boiling point of a liquid decreases because the atmospheric pressure also decreases with increase in height. The reduced temperatures at higher altitudes have no role as such in determining the boiling point of a liquid. It depends on the atmospheric pressure at that point. Hence option b is correct.
• A liquid boils, when its internal vapor pressure equals the outside atmospheric pressure. When one heats a tea kettle on a stovetop, he’s creating more water vapor; when the water’s vapor pressure rises enough to exceed the surrounding air pressure, bubbles start to form and the water boils. But pressure drops as one gains elevation. With that much less pressure, one does not need to apply as much heat to push vapour pressure of liquid beyond the surrounding atmospheric pressure – in other words, water boils at a lower temperature due to low atmospheric pressure.

Solution (c)

Explanation:

• Ascorbic Acid is a natural water-soluble vitamin (Vitamin C). Ascorbic acid is a potent reducing and antioxidant agent that functions in fighting bacterial infections, in detoxifying reactions, and in the formation of collagen in fibrous tissue. It is found in citrus and other fruits, and in vegetables. Hence Pair 1 is correct.
• Formic acid is the simplest carboxylic acid, containing a single carbon. It occurs naturally in various sources including the venom of bee and ant stings. Hence Pair 2 is correct.
• Oxalates — also known as oxalic acid — is a naturally-occurring compound in plants. These plant-based oxalates are consumed through our diet as well as produced as waste by your bodies. Oxalic acid is a natural product found in spinach and some other plant foods including rhubarb. Hence Pair 3 is incorrect.
• Tartaric Acid is a white crystalline dicarboxylic acid found in many plants, particularly tamarinds, grapes, unripe mangoes. Hence Pair 4 is correct.

Solution (b)

Explanation:

• Galvanization is a metal coating process in which a ferrous part is coated with a thin layer of zinc. The process of depositing a layer of zinc on iron is called galvanisation. The iron pipes we use in our homes to carry water are galvanised to prevent rusting. The zinc coating seals the surface from the environment, preventing oxidation and weathering from occurring. 

Solution (b)

Explanation:

• Neutrinos can be produced in various situations. The Sun, and all other stars, produce neutrinos copiously due to nuclear fusion and decay processes within their core. There are many other natural sources of neutrinos including exploding stars (supernovae), relic neutrinos (from the birth of the universe), natural radioactivity, and cosmic ray interactions in the atmosphere of the Earth. Hence Statement 1 is incorrect.
• A neutrino is a fermion that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is very small. Hence Statement 2 is correct.
• It can be artificially produced. Neutrinos can be produced by colliding a proton using a particle accelerator. Hence Statement 3 is incorrect.

These belong to the category of leptons. Leptons are the particles that interact through the so-called weak force. For this reason and because it is electrically neutral, neutrino interactions with matter are extremely rare. Quarks interact with the strong nuclear force. Protons and neutrons belong to the category of quarks. Hence Statement 4 is correct.

Solution (a)

Explanation:

• The substances which vapourise during burning, give flames. For example, kerosene oil and molten wax rise through the wick and are vapourised during burning and form flames. Charcoal, on the other hand, does not vapourise and so does not produce a flame. 

The outermost zone is the hottest part of the flame. This provides for maximum heat while burning ensuring quick process. Also, complete combustion takes place in this zone preventing any sort of blackening of metal. Hence, goldsmiths blow the outermost zone of a flame with a metallic blow-pipe for melting gold and silver.  Hence Statement a is correct.

Solution (b)

Explanation:

• The Pressurised Heavy Water Reactors (PHWRs) uses natural Uranium as fuel. PHWRs not only produce energy from natural uranium but also produce fissile plutonium (Pu)-239. The Fast Breeder Reactors (FBRs) use plutonium-239 (and not thorium) for generating electricity. Hence Statement 1 is incorrect.
• PHWR uses heavy water (deuterium oxide D2O) as its coolant and neutron moderator.  FBRs do not have a neutron moderator, and use less-moderating coolants such as liquid sodium, so its neutrons remain high-energy. Breeder reactors use a small core, which is important to sustain chain reactions. Hence Statement 2 is correct.

Solution (c)

Explanation:

When compared to stainless steel, Copper is a good conductor of heat and electricity. Using copper materials for the bottom of utensils is for easy transfer of heat to the raw materials. This makes cooking faster with less amount of heat. Hence option c is correct.

Solution (c)

Explanation:

• Fabrics are made up of yarns and yarns are further made up of fibres. The fibres of some fabrics such as cotton, jute, silk and wool are obtained from plants and animals. These are called natural fibres. For thousands of years natural fibres were the only ones available for making fabrics. In the last hundred years or so, fibres are also made from chemical substances, which are not obtained from plant or animal sources. These are called synthetic fibres. Some examples of synthetic fibres are polyester, nylon and acrylic. Hence, option c is the correct answer.

Solution (b)

Explanation:

• When the heavier component in a mixture settles after water is added to it, the process is called sedimentation. When the water (along with the dust) is removed, the process is called decantation. This principle is used for separating a mixture of two liquids that do not mix with each other. For example, oil and water from their mixture can be separated by this process. If a mixture of such liquids is allowed to stand for some time, they form two separate layers. The component that forms the top layer can then be separated by decantation. Hence, option b is the correct answer.

Solution (b)

Explanation:

Solution (c)

Explanation:

• Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state.
• Crystalline allotropes of carbon are Graphite, Diamond, Buckminsterfullerene and carbon nanotube. Amorphous allotropes of carbon are Coal, coke, wood charcoal, animal charcoal etc. Hence, options 1, 3 and 4 are correct. 
• Glass is not an allotrope of Carbon. Glass is a silicate. Hence, option 2 is incorrect.

Solution: (d)

Explanation:

The larger hole will lead to an increase in the steam going out leading to a greater reduction in temperature. Statement 1 is correct.

Temperature at which the food is cooked in a Pressure cooker is directly proportional to the temperature of the flame. Statement 2 is correct. 

By increasing the surface pressure on the liquid inside the closed cooker we can raise the cooking temperature. This pressure can be adjusted by changing the weight placed on the top of the cooker lid. Statement 3 is correct.

Solution: (a)  

Explanation: 

• Water is called the “universal solvent” because it can dissolve more substances than any other liquid. 
• It is due to water’s chemical composition and physical attributes that it is such an excellent solvent. Water molecules have a polar arrangement of oxygen and hydrogen atoms—one hand (hydrogen) has a positive electrical charge and the other hand(oxygen) has a negative charge. 
• This makes it possible for the water molecule to attract a wide range of other molecular species. Water can develop a strong attraction to another substance, such as salt (NaCl), to the point where it can interfere with the attractive forces holding the sodium and chloride in the salt complex together and dissolve it. 
• In organic chemistry, a dipolar compound or simply dipole is an electrically neutral molecule carrying a positive and a negative charge in at least one canonical description. Hence option (a) is correct answer.

Solution: (b)  

Explanation: 

• Photosynthesis- It is the process through which green plants and some other organisms convert light energy into chemical energy. 
• The functions of the chlorophyll, a green pigment, are related to the transformation of inefficient solar energy into useful chemical energy. The majority of the time, the photosynthetic process makes use of water and emits the oxygen that is vitally necessary for our continued existence. 

6H2O + 6CO2 → C6H12O6+ 6O2 

• Photosynthesis uses light energy for conversion of carbon dioxide and water into glucose and oxygen gas. 
• The potential energy stored in the molecular bonds of glucose convert into kinetic energy after cellular respiration. 
• Chemical bonds are a type of stored or “potential” energy because when the bonds break, energy is released. 
• Photosynthesis converts water and carbon dioxide into sugar and oxygen through sunlight as the catalyst. A by product of the photosynthesis process is the released oxygen into the atmosphere. 

Hence option (b) is correct.

Solution: (b)

Explanation:  

About Chemical Change: 

• It involves the transformation of one material into another, the creation of new materials with unique properties, and the creation of one or more new substances. 
• It happens when two compounds mix to create a new material (synthesis or either decomposes to form more substances). An example of a chemical change that results in a reaction is the oxidation reaction. Examples include burning wood, sour milk, cooking eggs, heating sugar to make caramel, and rusting iron. 

About Physical Change: 

• No new chemical species formed. 
• Since the identity of the matter does not change, changing a pure substance’s state from solid to liquid or gas constitutes a physical change. For instance: Ice melting, boiling water, sodium chloride crystallisation, etc.

Hence option (b) is correct answer.

Solution: (c)

 Explanation:

• After being harvested, fruits and vegetables stay metabolically active. Respiration is a manifestation of metabolic activity. The rate of respiration can be decreased effectively by lowering the temperature. 
• Fruits and vegetables can use the energy released during respiration for internal functions. To effectively store your fruit, controlling respiration is crucial. 
• The fruits and vegetables can be preserved in good condition as long as the respiration process can continue. The product will have to survive off of the nutrients it already has because it is no longer connected to the plant’s roots or other sections, so it won’t receive any additional nutrients. The fruits and veggies will therefore start to degrade after everything is done. 

Hence option (c) is correct answer.

Solution (c)

Explanation:

Context: The citizenship of Nauru, a tiny island nation spanning just eight square miles in the southwest Pacific Ocean, is now up for sale at a minimum of $105,000 (Rs 91.38 lakh), reported CNN. 

• Nauru is an island nation and a microstate in Oceania, located in the southwestern Pacific Ocean. Hence option c is correct.
• It is the smallest republic in the world with a land area of about 8 square miles and a population of 12,500.
• The island is about 1,300 km northeast of the Solomon Islands; its closest neighbour is the island of Banaba, in Kiribati, some 300 km to the east. 

Source: https://indianexpress.com/article/world/nauru-citizenship-91-lakh-island-country-9872494/ 

Solution (c)

Explanation:

Context: The first breeding site of the Blue-Cheeked Bee-eater (merops persicus) in peninsular India has been discovered in the saltpans of Aandivilai near the Manakudy Mangroves in Kanniyakumari district.

• Blue-cheeked Bee-Eater favours sub-tropical semi-desert regions. Hence statement 1 is correct.
• It is a near passerine bird in the bee-eater family, Meropidae.
• It was historically known as a passage migrant and winter visitor in India.
• Its breeding was primarily recorded in the Nile Delta, Pakistan, and Iran. Hence statement 2 is correct.
• It breeds mainly in sand deserts near bodies of water fringed with reeds and tamarisks.
• During the non-breeding season, it inhabits a wide variety of greener habitats including savanna, broad river valleys, woods, lakeshores, swamps, ponds, dams, waterworks, and cultivation.
• It may choose to nest solitarily or in small, loose colonies of up to ten individuals. It is also known to share colonies with European bee-eaters. 
• It is listed as least concern in the IUCN Red List. Hence statement 3 is incorrect.

Source: https://www.thehindu.com/sci-tech/energy-and-environment/first-breeding-record-of-blue-cheeked-bee-eater-discovered-in-peninsular-india/article69242534.ece

Solution (c)

Explanation:

Context:

• Komagata Maru Incident (1914) 
• Montford Reforms (1919) 
• Muddiman Committee (1924) 
• Hartog Committee (1929)

Hence option c is correct.

Solution (c)

Explanation:

Context: India’s gaming industry has seen remarkable growth, particularly in digital and online gaming, which has become one of the fastest-growing sectors in the country’s media and entertainment landscape. To support this growth the Bharat Tech Triumph Program (TTP) has been launched as part of the Create in India Challenge Season 1. 

• Bharat Tech Triumph Program aims to identify and showcase India’s gaming talent on the international stage. Hence statement 1 is correct.
• It is open to individuals and organizations involved in gaming development, esports, and business solutions critical to the gaming ecosystem.
• It is organized by the Interactive Entertainment and Innovation Council (IEIC) in partnership with the Ministry of Information and Broadcasting (MIB) the program. Hence statement 2 is correct.

Source: https://pib.gov.in/PressReleaseIframePage.aspx?PRID=2105340 

Solution (d)

Explanation:

Context: An innovative method to minimize anion migration in perovskite nanocrystals, thereby reducing their sensitivity to heat and moisture, as well as colour instability, paving the way for efficient, durable optoelectronic devices.

Perovskite Nanocrystal is a material that has the same crystal structure as the mineral calcium titanium oxide (CaTiO3). The applications of Perovskite Nanocrystal:

• Photovoltaic solar cells
• Photodetectors
• Lasers 
• Solar cells
• Light-emitting devices

Hence option d is correct.

Source: https://pib.gov.in/PressReleaseIframePage.aspx?PRID=2105309 

Solution (b)

Explanation:

Context: The Prime Minister will attend the Jhumoir Binandini (Mega Jhumoir) 2025, a spectacular cultural extravaganza with 8,000 performers participating in the Jhumoir dance, a folk dance of Assam Tea Tribe and Adivasi Communities of Assam that embodies the spirit of inclusivity, unity, and cultural pride, and symbolizes Assam’s syncretic cultural mélange. The Mega Jhumoir event symbolizes 200 years of the tea industry, and also 200 years of industrialization in Assam.

Hence option b is correct.

Source: https://pib.gov.in/PressReleaseIframePage.aspx?PRID=2105467 

Solution (c)

Explanation:

Context: After softening for three quarters in a row, the Composite Flash Purchasing Managers’ Index (PMI) rose at a faster pace in February, showing an uptick in the growth of the private sector in the current quarter, says an HSBC report.

• The Purchasing Managers’ Index is an indicator of business activity in both the manufacturing and services sectors. Hence statement 1 is correct.
• It is a survey-based measure that asks the respondents about changes in their perception of some key business variables from the month before.
• It is calculated separately for the manufacturing and services sectors and then a composite index is constructed.
• There are two types of PMI — Manufacturing PMI and Services PMI.
• It helps in determining whether the market conditions, as seen by purchasing managers, are expanding, contracting, or staying the same. Hence statement 2 is correct.

Source: https://indianexpress.com/article/business/economy/composite-flash-pmi-rises-first-time-three-quarters-9849275/ 

Solution (c)

Explanation:

Context: The XR Creator Hackathon, organized under the Information and Broadcasting Ministry’s “WAVES” initiative, provided him with a platform to showcase his ideas.

• WAVES 2025 is an initiative of the Ministry of Information and Broadcasting, Government of India. Hence statement 1 is correct.
• It will serve as a forum for India to position itself as a global leader in content creation, technology integration, and creative industry growth.
• It is designed as a pivotal platform for ideas, collaboration, and innovation within the media and entertainment (M&E) industry. Hence statement 2 is correct.

Source: https://www.thehindu.com/news/national/waves-2025-xr-creator-hackathon-opens-up-opportunities-for-myriad-talents/article69255276.ece

Solution (a)

Explanation:

Context: Tamil Nadu Chief Minister M K Stalin has announced an all-party meeting to galvanize “political consensus” in the state on the looming delimitation exercise.

• Delimitation means the act or process of fixing limits or boundaries of territorial constituencies in a country or a province having a legislative body. The job of delimitation is assigned to a high-power body. Such a body is known as the Delimitation Commission or a Boundary Commission.
• The Delimitation Commission in India is a high-power body whose orders have the force of law and cannot be called into question before any court. These orders come into force on a date to be specified by the President of India on this behalf. Hence statement 1 is correct.
• The copies of its orders are laid before the Lok Sabha and the State Legislative Assembly concerned, but no modifications are permissible therein by them. Hence statement 2 is incorrect.

Source: https://indianexpress.com/article/cities/chennai/stalin-all-party-meet-delimitation-tn-rights-9856013/

Solution (d)

Explanation:

Context: Donald Trump has announced plans to offer a “gold card” visa that can be bought for $5 million (Rs 43.5 crore approximately) as a route to American citizenship.

The proposed Golden Visa will replace the existing EB-5 visa for foreign investors, which grants residency to those who invest $800,000 (Rs 7 crore) to $1 million (Rs 8.71 crore) and create at least 10 jobs. It allows direct purchase of a Green Card for $5 million. Hence option d is correct.

Source: https://indianexpress.com/article/india/donald-trump-offers-5-million-gold-card-visas-for-us-citizenship-9858305/

Solution (d) 

Statement analysis:

Inference 1 is incorrect: The passage specifies that despite infrastructure, people avoid using it and practice open defecation as seen in the lines, “… and economic factors may impair people from using or avoiding infrastructure considered safe and hygienic by environmental and health standards.” Also, the passage does not exclusively mention that there is a lack of infrastructure. So, the inference that there is a need to build infrastructure is not correct as per the passage.  

Inference 2 is incorrect: The passage mentions the issues of open defecation in developing countries as seen in the lines, “Open defecation is a serious sanitation issue most developing countries are battling with.” But to extrapolate it and conclusively state that developed countries do not face this issue would not be based on the information contained in the passage. So, this inference is not valid.

Test explain

Solution (a) 

Statement analysis:

Option (a) is correct: The passage is about open defecation, how it continues due to the lack of cultural acceptance in society, and how inclusive policies would be needed to solve this. It is seen in the lines, “Understanding the sociocultural and economic factors underlying open defecation is therefore crucial for any policy aimed at eradicating the practice. Finally, community-led initiatives that draw on the creativity and capacity of local people to take control of their change processes must be integrated into open defecation intervention programs.” These lines validate the given option. 

Option (b) is incorrect: The given option is generic and not specific to the core theme of the passage. The core theme is to understand the reasons for continued open defecation and suggest measures to eradicate it as captured in option (a). This option merely states that sanitation is needed for eradication. So, this is not the best crux of the passage.  

Option (c) is incorrect: The passage clearly mentions community participation as a tool for the eradication of open defecation. It is reflected in the last line of the passage, “Finally, community-led initiatives that draw on the creativity and capacity of local people to take control of their change processes must be integrated into open defecation intervention programs.” Therefore, it would be incorrect to say that policies alone (without community participation) would be sufficient to eradicate open defecation. 

Option (d) is incorrect: The given option does not cover the core theme of the passage which is the reason for open defecation and the solution suggested. This option only mentions that it is a normal act, which does not signify anything related to the core theme of the passage. So, this is not the best crux of the passage. 

ed

Solution (d)  

Explanation:

The number is in the form of 9x + 1, where x is the quotient. 

If x = 1, p = 10. It’s an even number.  

If x = 2, p = 19. It’s an odd number.  Hence, option (d) is correct. 

Solution (a)

Explanation:

Venn diagram:  

So, only conclusion I follows. 

Hence, option (a) is the correct answer.

Solution (c) 

Explanation:

The next term of the sequence is half of the previous term. 

So, the term after 1 will be ½ 

Hence, option (c) is the correct answer.