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The correct answer is It is a highly endothermic reaction.

Key Points

• In the given reaction, aluminum (Al) displaces iron (Fe) from iron(III) oxide (Fe2O3), resulting in the formation of iron and aluminum oxide. Hence, it is an example of displacement reaction.
• Displacement reactions, such as the one shown in the equation, are typically exothermic.
• The transfer of electrons between the reactants releases energy. It means it is an exothermic reaction. Hence, option 2 is incorrect.
• In this case, aluminum is oxidized (loses electrons), and iron(III) oxide is reduced (gains electrons).
• The overall reaction is exothermic.
• In the given reaction, iron(III) oxide (Fe2O3) is reduced to form iron (Fe), indicating that Fe2O3 acts as an oxidizing agent, as it accepts electrons from aluminum.
• The reaction between iron(III) oxide and aluminum is used in thermite welding, which is a method of joining metal pieces, including railway tracks.
• The intense heat generated during the reaction melts the iron and aluminum oxide, facilitating the welding process.

The correct answer is contraception.

• Contraception is the method by which Copper-T is placed in the uterus.

Key Points

• Contraception:
• It is also known as birth control.
• It is a method used to prevent pregnancy.
• Methods of contraception:
• combined pill
• condoms
• contraceptive injection
• contraceptive patch
• diaphragms
• intrauterine device (IUD) (Copper-T)
• intrauterine system (IUS)
• Copper-T is placed in the uterus.

CONCEPT:

Plaster of Paris

• Plaster of Paris is primarily composed of Calcium Sulphate Hemihydrate (CaSO₄·½H₂O).
• It is a quick-setting material obtained by heating gypsum (CaSO₄·2H₂O) to approximately 150°C.
• During heating, gypsum loses water molecules and forms Calcium Sulphate Hemihydrate, which is commonly known as Plaster of Paris.
• The chemical reaction is as follows:

CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O (on heating)

EXPLANATION:

• Plaster of Paris is widely used in construction, art, and medical applications due to its ability to set quickly when mixed with water.
• When mixed with water, it reabsorbs the lost water molecules and forms gypsum again:

CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O

 Additional Information

• Potassium Chloride - Not related to Plaster of Paris.
• Calcium Carbonate - It is a different compound with no connection to Plaster of Paris.
• Sodium Chloride - Common table salt, not relevant here.

Therefore, the primary constituent of Plaster of Paris is Calcium Sulphate Hemihydrate.

Iris is the coloured part of the eye that controls the amount of light that enters the eye. It can expand or contract to control the amount of light entering the eye.

Visual Defects: When a person is not able to see objects with ‘normal’ vision, he is said to have visual defects. The criterion for a person to have normal vision is if he can see an object of 1.5 mm length from 5 meters.

Key Points

The visual defects are of two types:

Hyperopia (or farsightedness):

• When a person can see far objects but can’t see near objects, he is said to have hyperopia.
• It is a refractive error, which means that the eye does not bend or refract light properly to a single focus to see images clearly.
• In hyperopia, distant objects look somewhat clear, but close objects appear more blurred.
• It is most commonly known as farsightedness, which results from the failure of the cornea.

Myopia (or nearsightedness):

• Nearsightedness (myopia) is a common vision condition in which you can see objects near to you clearly, but objects farther away are blurry.

It occurs when the shape of your eye causes light rays to bend (refract) incorrectly, focusing images in front of your retina instead of on your retina.

Hence, we conclude that farsightedness is also called hyperopia.

• White blood cells are an important part of the immune system which helps in fighting infections by attacking bacteria, viruses, and germs that invade the body.
• White blood cells are also known as leukocytes.
• They help in protecting the body against both infectious disease and foreign invaders.
• WBC are produced in the bone marrow.

The correct answer is Habitat Loss and Fragmentation

Key Points

• Habitat Loss and Fragmentation: It is the main cause of extinction globally.
• The destruction and division of natural environments drastically reduce the area available for species to survive and thrive.
• A prime example of this threat is the massive reduction of rainforests, which formerly covered 14% of the Earth's surface but now cover merely 6%.
• The ongoing clearing of the Amazon Rainforest for soy cultivation and beef production further exemplifies how severe habitat loss directly drives active species extinction.

Additional Information

• Overexploitation: This threat involves the excessive use of natural resources for activities like farming and gathering fuelwood, leading to the creation of wastelands. An example is the loss of mangroves due to aquaculture expansion.
• Co-extinction: This ecological phenomenon occurs when the extinction of one species causes the inevitable extinction of others that strictly depend on it, such as specific host-parasite relationships.
• Invasive Alien Species: Non-native species introduced into a new environment outcompete native organisms for resources. Examples in India include Lantana, Water hyacinth, and Eucalyptus.
• Climate Change: Rapid environmental shifts cause the destruction of essential habitats, such as coral reefs, and the loss of food sources, posing a severe threat to animals like polar bears.

Important Points

• The combined impact of these threats has resulted in a 68% average population decline in mammals, birds, fish, reptiles, and amphibia since 1970, as documented by the WWF Living Planet Report 2020.

The correct answer is double displacement reaction.

Key Points

• A double displacement reaction occurs when two compounds exchange ions to form two new compounds.
• In the given reaction: AgNO₃ + NaCl → AgCl + NaNO₃, the silver ion (Ag⁺) and sodium ion (Na⁺) exchange their anions (NO₃^- and Cl^- respectively).
• The product AgCl is a white precipitate, which confirms the reaction as a double displacement reaction.
• This type of reaction is commonly observed in aqueous solutions, especially when one of the products is insoluble and precipitates out.
• Double displacement reactions are also known as precipitation reactions when a solid precipitate is formed.

Additional Information

• Double Displacement Reaction:
• It is a chemical reaction where two compounds exchange their ions to form two new compounds.
• The general formula is: AB + CD → AD + CB.
• These reactions often occur in aqueous solutions.
• Examples include neutralization reactions and precipitation reactions.
• Precipitation Reaction:
• A type of double displacement reaction where an insoluble substance (precipitate) is formed.
• Example: BaCl₂ + Na₂SO₄ → BaSO₄ (precipitate) + 2NaCl.
• Precipitates are generally indicated by a solid (↓) in chemical equations.
• Combination Reaction:
• A reaction where two or more reactants combine to form a single product.
• Example: 2H₂ + O₂ → 2H₂O.
• Decomposition Reaction:
• A reaction where a single compound breaks down into two or more simpler products.
• Example: 2HgO → 2Hg + O₂.
• Displacement Reaction:
• A reaction where one element replaces another in a compound.
• Example: Zn + CuSO₄ → ZnSO₄ + Cu.

The correct answer is Pituitary.

Key Points

• Pituitary: The pituitary gland, which hangs by a thin stalk from the hypothalamus, is called the master gland of the body because it regulates the activity of the endocrine glands.
• Spleen: It is the largest organ in the lymphatic system. It is an important organ for keeping bodily fluids balanced. It is located under the ribcage and above the stomach in the left upper quadrant of the abdomen
• Typhus: Typhus fevers are a group of diseases caused by bacteria that are spread to humans by fleas, lice, and chiggers
• Brunner gland: It helps in secreting of alkaline-based mucus to protect the duodenal lining from the acid secreted in the stomach

Correct answer is V = I R

Key Points

• Ohm's Law (E = IR) is as fundamentally important as Einstein's Relativity equation (E = mc²) is to physicists.
• When spelled out, it means voltage = current x resistance, or volts = amps x ohms, or V = A x Ω.
• Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
• One of the most basic and important laws of electric circuits is Ohm's law.

Additional Information

• Archimede's Principle states that a body immersed in a fluid experiences an upthrust equal to the weight of the fluid displaced, and this is fundamental to the equilibrium of a body floating in still water.​
• Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.
• Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it.