CBSE Board Class 10 Science Question Paper 2025 Set 1 (31-6-1) Available- Download Solution PDF with Answer Key

Step 1: Understanding the setup.
In the electrolysis of water, at the anode (R), oxygen gas (O\textsubscript{2) is released, and at the cathode (S), hydrogen gas (H\textsubscript{2) is released.

Step 2: Assigning the correct gases to P and Q.

- \( P \) corresponds to oxygen gas, which is released at the anode (R), so \( P \) should be associated with oxygen gas and anode.

- \( Q \) corresponds to hydrogen gas, which is released at the cathode (S), so \( Q \) should be associated with hydrogen gas and cathode.

Step 3: Conclusion.
Thus, the correct matching is (i) and (iii), corresponding to option (C). Quick Tip: During electrolysis, oxidation occurs at the anode (producing oxygen), and reduction occurs at the cathode (producing hydrogen).

Step 1: Understanding the solutions.

- Potassium nitrate (A) is a neutral salt, so its pH is near 7.

- Ammonium chloride (B) is an acidic salt, so its pH is less than 7.

- Sodium carbonate (C) is a basic salt, so its pH is greater than 7.


Step 2: Ascending order of pH.
Thus, the ascending order of pH is C \(<\) A \(<\) B, corresponding to option (C). Quick Tip: When a salt is formed from a weak acid and a strong base, it is basic in nature. When formed from a strong acid and a weak base, it is acidic.

Step 1: Understanding the burning of magnesium ribbon.

- When magnesium ribbon burns in air, it produces a dazzling white flame and forms a white powder of magnesium oxide (MgO), which is an exothermic reaction.

- The reaction between magnesium and oxygen is a combination reaction where two reactants combine to form a product.

Step 2: Conclusion.
The burning of magnesium is an exothermic reaction, not endothermic. Therefore, statement (C) is incorrect. Quick Tip: The burning of magnesium in air is a combination reaction (Mg + O\textsubscript{2} → MgO) and it releases heat, making it exothermic.

Step 1: Identifying the homologous series

• C₄H₁₀ is part of the alkane group.
• C₆H₁₄ is also part of the alkane group.
• C₇H₁₄ is part of the alkane group too.
• C₁₀H₂₂ is a larger alkane, but it does not belong to the same group.

Step 2: Conclusion

So, the correct answer is option (D) C₁₀H₂₂.

Quick Tip: Alkanes follow the formula CₙH₂ₙ₊₂. If a compound doesn't fit this formula, it belongs to a different group.

Step 1: Reaction of iron nails with copper sulphate.
When iron nails are placed in copper sulphate solution, a displacement reaction occurs, where iron displaces copper from its salt, forming iron(II) sulfate and copper.

Step 2: Conclusion.
The resulting colour of the solution changes to pale green, indicating the formation of iron(II) sulfate. Quick Tip: In displacement reactions, a more reactive metal can displace a less reactive metal from its salt solution.

Step 1: Identifying the chemical compound.
Tamarind juice is acidic due to the presence of tartaric acid, which is a weak acid.

Step 2: Conclusion.
Therefore, the correct answer is tartaric acid. Quick Tip: Tartaric acid is commonly found in tamarind and gives the juice its characteristic sour taste.

Step 1: Understanding water of crystallization.
Water of crystallization refers to the water molecules that are part of the crystal structure of certain salts.


Step 2: Analyzing each compound.
- Bleaching Powder: Contains water of crystallization.

- Washing Soda: Also contains water of crystallization.

- Plaster of Paris: Contains water of crystallization.

- Baking Soda: Does not contain water of crystallization.


Step 3: Conclusion.
Therefore, the correct answer is option (C), which includes Bleaching Powder and Washing Soda. Quick Tip: Water of crystallization is important in determining the properties of salts, and it is typically lost when salts are heated.

Step 1: Identifying the traits.
Tall (T) is dominant to short (t), and round (R) is dominant to wrinkled (r).

 The parental genotypes are TTRR (tall, round) and ttrr (short, wrinkled).

Step 2: Analyzing the F\textsubscript{1} generation.
 The F\textsubscript{1 generation will inherit one allele from each parent.

 All F\textsubscript{1 plants will have the genotype TtRr, making them heterozygous for both traits.

Step 3: Conclusion.
Since tall (T) and round (R) are both dominant, all F\textsubscript{1 plants will be tall with round seeds. Quick Tip: In genetic crosses, the dominant trait is always expressed in the offspring if at least one dominant allele is present.

Step 1: Understanding the function of the glands.

- The Hypothalamus is located in the brain and regulates many bodily functions, including hormone release.

- The Pineal gland is also located in the brain and is responsible for regulating sleep-wake cycles by releasing melatonin.


Step 2: Analyzing the options.

- Option (A) includes Parathyroid, which is not located in the brain, so it is incorrect.

- Option (B) includes Thymus, which is located in the chest, not the brain, so it is incorrect.

- Option (C) includes Thymus again, so it is also incorrect.

- Option (D) is correct, as both the Hypothalamus and Pineal gland are located in the brain.
Quick Tip: Endocrine glands secrete hormones directly into the bloodstream, helping regulate various physiological processes in the body.

Understanding the modes of reproduction.

- Leishmania reproduces by Binary fission (P-3).

- Spirogyra reproduces by Fragmentation (Q-4).

- Planaria reproduces by Regeneration (R-1).

- Plasmodium reproduces by Multiple fission (S-2).

Step 2: Conclusion.
The correct matching is option (C): P-3, Q-4, R-1, S-2. Quick Tip: Different organisms exhibit various modes of asexual reproduction, such as binary fission, fragmentation, and regeneration, depending on the species.

Step 1: Identifying the basic filtration unit.
The nephron is the functional unit of the kidney responsible for filtering the blood and forming urine.

Step 2: Conclusion.
Thus, the correct answer is option (A): Nephron. Quick Tip: The nephron plays a crucial role in regulating the body's fluid and electrolyte balance and in removing waste products through urine.

Step 1: Understanding the gastric juice composition.
The gastric glands secrete hydrochloric acid (HCl), which helps in the digestion of food and maintains the acidic environment of the stomach. Pepsin, an enzyme, breaks down proteins, and mucus protects the stomach lining from the acid.

Step 2: Conclusion.
Thus, the correct answer is option (B): Hydrochloric acid, Pepsin, Mucus. Quick Tip: The stomach secretes gastric juices that aid in digestion, and the protective mucus prevents damage to the stomach lining from acidic conditions.

Step 1: Understanding the ray diagram.
A concave mirror forms an image that is reflected in a path determined by the focus (F) and the center of curvature (C). The correct ray diagram will show the reflected ray passing through the focus or focal point.

Step 2: Analyzing the options.
- Option (C) depicts the correct reflected ray path for the concave mirror.

Step 3: Conclusion.
Thus, the correct answer is option (C). Quick Tip: When dealing with concave mirrors, the reflection depends on the incident ray’s position relative to the focal point and center of curvature.

Step 1: Identifying the structure.
The iris is the part of the human eye that controls the size of the pupil and, in turn, regulates the amount of light entering the eye.

Step 2: Conclusion.
Thus, the correct answer is option (A): Iris. Quick Tip: The iris is a colored part of the eye and controls the dilation and constriction of the pupil to control light intake.

Step 1: Understanding energy transfer.
In an energy pyramid, energy decreases as you move up trophic levels. Typically, only about 10% of the energy is transferred to the next trophic level.

Step 2: Calculation.
If the energy at the third trophic level is 50 kJ, then the energy available at the producer level (first trophic level) can be calculated by multiplying by 100.
\[ Energy at producer level = 50 \, kJ \times 100 = 5000 \, kJ \]

Step 3: Conclusion.
Thus, the correct answer is option (D): 5000 kJ. Quick Tip: In a food chain, only about 10% of the energy is transferred to each successive trophic level. This explains the large energy available at the producer level.

Step 1: Analyzing the statements.

- Ozone (O\textsubscript{3) is a protective layer in the Earth's atmosphere that absorbs harmful UV radiation.

- While ozone is toxic at high concentrations, it is not considered a "deadly poisonous gas" in the context of the atmosphere.


Step 2: Conclusion.
Thus, the incorrect statement is option (A). Quick Tip: Ozone is essential for life on Earth as it protects the planet from the sun's harmful ultraviolet radiation.

Step 1: Understanding Assertion (A).
Carbon and its compounds, such as fossil fuels (coal, petroleum), are major sources of energy and have been used for combustion for heat and power.

Step 2: Understanding Reason (R).
The burning of carbon compounds like hydrocarbons releases a significant amount of heat and light due to the energy stored in the chemical bonds.

Step 3: Conclusion.
Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains why carbon compounds are major fuel sources. Hence, the correct answer is option (A). Quick Tip: Carbon compounds, when burned, undergo combustion, releasing heat and light due to their high energy content, making them essential as fuel sources.

Step 1: Understanding Xylem Tissue.
Xylem is responsible for the transport of water and minerals from the roots to the rest of the plant. This function is crucial for plant nutrition and hydration.

Step 2: Analyzing Reason (R).
While xylem tissue is indeed found in the roots, it is also present in stems and leaves of plants. Therefore, Reason (R) is false, as xylem is not exclusive to the roots.

Step 3: Conclusion.
The correct answer is option (C) since Assertion (A) is true, but Reason (R) is false. Quick Tip: Xylem is essential for water and nutrient transport in plants, and it exists in the roots, stems, and leaves.

Step 1: Understanding Assertion (A).
In domestic circuits, the earth wire is connected to a metallic plate that is buried in the earth to provide a safe path for electric current in case of a fault.

Step 2: Understanding Reason (R).
The earth wire maintains the electrical potential of the appliance at the same level as the earth, ensuring the safety of the user by preventing severe electric shocks.

Step 3: Conclusion.
Since both Assertion (A) and Reason (R) are true, and Reason (R) explains why the earth wire is used, the correct answer is option (A). Quick Tip: The earth wire is an essential safety feature in electrical circuits, providing a route for excess current to flow safely into the earth.

Step 1: Understanding Food Web.
A food web is a network of interconnected food chains within an ecosystem, illustrating how different species are related through feeding.

Step 2: Analyzing Reason (R).
Food webs actually increase the stability of an ecosystem by providing alternative pathways for energy flow, meaning that if one species declines, others can take its place.

Step 3: Conclusion.
Since Assertion (A) is true but Reason (R) is false, the correct answer is option (C). Quick Tip: A food web improves ecosystem resilience, as it reduces the impact of species loss on the overall balance of the ecosystem.

Step 1: Identifying metals.
- Metal 'P' (Cu) is displaced by metal 'Q' (Zn) in the solution.
- Zinc (Zn) is more reactive than copper (Cu), as shown in the reactivity series, which allows zinc to displace copper from its sulphate solution.

Step 2: Writing the chemical equation.
The reaction can be represented as: \[ Zn (s) + CuSO_4 (aq) \rightarrow Cu (s) + ZnSO_4 (aq) \]

Step 3: Conclusion from the reactivity series.
- Zinc (Zn) is more reactive than Copper (Cu), and this is consistent with the reactivity series of metals. More reactive metals can displace less reactive metals from their compounds. Quick Tip: When a more reactive metal displaces a less reactive metal from its solution, this is called a displacement reaction. The reactivity series can help predict which metal will displace another.

The brain is protected by the skull, which forms a hard, bony protective layer around it. Additionally, the brain is cushioned by the cerebrospinal fluid (CSF), which helps to absorb shocks and impacts. The meninges, which are three protective membranes, further shield the brain from injury. Quick Tip: The brain's protection comes from physical barriers like the skull and membranes, as well as the cushioning effect of cerebrospinal fluid.

The part of the brain responsible for maintaining posture and balance is the cerebellum. The cerebellum controls voluntary movements and helps in maintaining body posture and balance by coordinating muscular activity. Quick Tip: The cerebellum plays a vital role in balance and coordination. Any damage to this region can lead to loss of balance and difficulty in movement.

Proteins are responsible for the expression of genetic traits through their role in gene expression and regulation. For example, in plants, the height or "tallness" characteristic can be controlled by the production of specific proteins. A gene encoding a growth hormone or related protein will direct the plant to grow taller. This process involves transcription and translation of genetic material to produce the necessary proteins that control cell division and elongation, contributing to the overall height. Quick Tip: Proteins are the end products of genes and are directly involved in traits like tallness in plants by regulating growth processes.

In sexually reproducing organisms, inheritance occurs through the passing of genetic material (DNA) from both parents. DNA from both the father and the mother combines during fertilization, resulting in offspring with a genetic makeup that is a combination of both parents. The process ensures the stability of DNA by maintaining the integrity of genes through generations, with mechanisms such as genetic recombination and mutation correction playing key roles in stabilizing the DNA. Quick Tip: Sexual reproduction ensures genetic diversity and stability of DNA through the combination of genetic material from both parents.

The speed of light is more in Medium 1 as the refracted ray bends away from the normal when it enters Medium 2, which suggests that the speed of light in Medium 1 is higher. Quick Tip: The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in that medium. The bending of light depends on the relative speed in different media.

The bending of the refracted ray away from the normal is due to the difference in the speed of light in the two media. Light travels faster in Medium 1, and when it enters Medium 2, where the speed of light is slower, the ray bends away from the normal as per Snell's Law. Quick Tip: The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in that medium. The bending of light depends on the relative speed in different media.

The refractive index of Medium 2 with respect to Medium 1 is given by the formula: \[ n_{2/1} = \frac{c_1}{c_2} \]
Where:
 \( c_1 \) is the speed of light in Medium 1,
 \( c_2 \) is the speed of light in Medium 2. Quick Tip: The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in that medium. The bending of light depends on the relative speed in different media.

At very high altitudes, passengers are above the atmosphere where there is less scattering of sunlight. As a result, they do not see the scattered blue light and the sky appears dark, similar to the condition experienced by astronauts in space.



(ii) 'Danger' signal lights are red in color.
Red light has the longest wavelength and the least scattering in the atmosphere. This makes red light more visible over longer distances, which is why it is used for 'Danger' signals.

(b) A rainbow is a meteorological phenomenon caused by reflection, refraction, and dispersion of light, which results in a spectrum of light appearing in the sky. It occurs when sunlight passes through raindrops, breaking the light into its constituent colors. We see a rainbow only after rainfall because the raindrops act as prisms, refracting and dispersing the light, and the sky is clear enough for sunlight to shine through.

Quick Tip: The refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in that medium. The bending of light depends on the relative speed in different media.

Natural ponds and lakes have a self-cleaning system where natural processes such as filtration, sedimentation, and biological processes help maintain water quality. However, aquariums and swimming pools are enclosed and do not have these natural processes, which is why they require regular cleaning and maintenance to prevent the accumulation of waste and maintain clean water. Quick Tip: Natural water bodies are self-sustaining with natural processes for cleaning, while artificial water bodies need maintenance due to their controlled environment.

When steam is passed over red-hot iron, iron reacts with water vapor to form iron oxide and hydrogen gas. The balanced chemical equation for this reaction is: \[ 3Fe (s) + 4H_2O (g) \rightarrow Fe_3O_4 (s) + 4H_2 (g) \]
In this reaction, iron (Fe) reacts with steam (water vapor, H\textsubscript{2O) to form iron oxide (Fe\textsubscript{3O\textsubscript{4) and hydrogen gas (H\textsubscript{2). Quick Tip: Balancing chemical equations requires ensuring that the number of atoms on both sides of the equation is the same. In combustion and respiration reactions, oxygen is crucial, and the products are often carbon dioxide and water.

Natural gas primarily consists of methane (CH\textsubscript{4). When methane is burned in air (which provides oxygen), it reacts to form carbon dioxide and water. The balanced chemical equation for this combustion reaction is: \[ CH_4 (g) + 2O_2 (g) \rightarrow CO_2 (g) + 2H_2O (g) \]
In this reaction, methane (CH\textsubscript{4
) reacts with oxygen (O\textsubscript{2) to form carbon dioxide (CO\textsubscript{2) and water vapor (H\textsubscript{2O). Quick Tip: Balancing chemical equations requires ensuring that the number of atoms on both sides of the equation is the same. In combustion and respiration reactions, oxygen is crucial, and the products are often carbon dioxide and water.

In our body, glucose (C\textsubscript{6H\textsubscript{12O\textsubscript{6) reacts with oxygen (O\textsubscript{6) to produce carbon dioxide (CO\textsubscript{2), water (H\textsubscript{2O), and energy. This reaction is part of cellular respiration, which is an exothermic process that provides energy for our cells. The balanced chemical equation for this process is: \[ C_6H_{12}O_6 (aq) + 6O_2 (g) \rightarrow 6CO_2 (g) + 6H_2O (l) + energy \]
This process provides the energy necessary for the various biological functions of our body. Quick Tip: Balancing chemical equations requires ensuring that the number of atoms on both sides of the equation is the same. In combustion and respiration reactions, oxygen is crucial, and the products are often carbon dioxide and water.

Baking soda (NaHCO\textsubscript{3) acts as an anti-acid due to its ability to neutralize excess stomach acid. When baking soda reacts with hydrochloric acid (HCl) in the stomach, it produces sodium chloride (NaCl), carbon dioxide (CO\textsubscript{2), and water (H\textsubscript{2O), which relieves the acidity. The chemical equation is: \[ NaHCO_3 (aq) + HCl (aq) \rightarrow NaCl (aq) + CO_2 (g) + H_2O (l) \]
Thus, the chemical property utilized here is its ability to neutralize acids. Quick Tip: Baking soda is a versatile compound: It acts as an anti-acid, a leavening agent in baking, and helps extinguish fires by producing carbon dioxide when it reacts with acids.

Baking powder contains baking soda as one of its ingredients. When baking soda reacts with an acid like cream of tartar or vinegar, carbon dioxide gas is produced, causing the dough to rise. This reaction is the basis for baking soda's role in baking powder. The chemical equation is: \[ NaHCO_3 (aq) + H_2C\textsubscript{4}H\textsubscript{4}O\textsubscript{6} (aq) \rightarrow NaKC\textsubscript{4}H\textsubscript{4}O\textsubscript{6} (aq) + CO_2 (g) + H_2O (l) \]
Here, the acid-base reaction produces carbon dioxide that helps in leavening the dough. Quick Tip: Baking soda is a versatile compound: It acts as an anti-acid, a leavening agent in baking, and helps extinguish fires by producing carbon dioxide when it reacts with acids.

In soda-acid fire extinguishers, baking soda reacts with an acid (like sulfuric acid) to release carbon dioxide gas, which helps extinguish the fire by displacing oxygen. The chemical equation for this reaction is: \[ NaHCO_3 (aq) + H_2SO_4 (aq) \rightarrow NaHSO_4 (aq) + CO_2 (g) + H_2O (l) \]
Thus, the chemical property used here is the production of CO\textsubscript{2 when it reacts with acids. Quick Tip: Baking soda is a versatile compound: It acts as an anti-acid, a leavening agent in baking, and helps extinguish fires by producing carbon dioxide when it reacts with acids.

When an acid reacts with a metal, a salt and hydrogen gas are produced. For example, when zinc (Zn) reacts with hydrochloric acid (HCl), zinc chloride (ZnCl\textsubscript{2) and hydrogen gas (H\textsubscript{2) are formed. The chemical equation is: \[ Zn (s) + 2HCl (aq) \rightarrow ZnCl_2 (aq) + H_2 (g) \] Quick Tip: Acid-base reactions always produce salt and water. Acids reacting with metals or carbonates can also produce hydrogen gas or carbon dioxide.

When an acid reacts with a base, a salt and water are produced in a neutralization reaction. For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), sodium chloride (NaCl) and water (H\textsubscript{2O) are formed. The chemical equation is: \[ HCl (aq) + NaOH (aq) \rightarrow NaCl (aq) + H_2O (l) \] Quick Tip: Acid-base reactions always produce salt and water. Acids reacting with metals or carbonates can also produce hydrogen gas or carbon dioxide.

When an acid reacts with a carbonate, a salt, carbon dioxide (CO\textsubscript{2), and water are produced. For example, when hydrochloric acid (HCl) reacts with sodium carbonate (Na\textsubscript{2CO\textsubscript{3), sodium chloride (NaCl), carbon dioxide (CO\textsubscript{2), and water (H\textsubscript{2O) are formed. The chemical equation is: \[ Na_2CO_3 (aq) + 2HCl (aq) \rightarrow 2NaCl (aq) + CO_2 (g) + H_2O (l) \] Quick Tip: Acid-base reactions always produce salt and water. Acids reacting with metals or carbonates can also produce hydrogen gas or carbon dioxide.

(i) Oxygenated blood:
The blood vessel that brings oxygenated blood to the human heart is the pulmonary vein. This vein carries oxygen-rich blood from the lungs to the left atrium of the heart.

(ii) Deoxygenated blood:
The blood vessel that brings deoxygenated blood to the human heart is the superior and inferior vena cava. These veins carry deoxygenated blood from the body back to the right atrium of the heart.

Chamber receiving deoxygenated blood:
The chamber of the heart that receives deoxygenated blood is the right atrium. Blood flows into this chamber from the superior and inferior vena cava.

How deoxygenated blood is sent to the lungs for oxygenation:
Once deoxygenated blood enters the right atrium, it is pumped into the right ventricle, which then contracts to send the blood through the pulmonary artery to the lungs for oxygenation. The pulmonary artery carries the deoxygenated blood to the lungs, where it exchanges carbon dioxide for oxygen. Quick Tip: The pulmonary circulation moves deoxygenated blood to the lungs for oxygenation, while the systemic circulation moves oxygenated blood to the body. The pulmonary veins and arteries carry blood in the opposite directions compared to other veins and arteries in the body.

Mendel made the following observations in the F\textsubscript{1 generation:

1. All plants in F\textsubscript{1 generation had purple flowers, indicating that the purple flower trait was dominant over the white flower trait.

2. The F\textsubscript{1 plants were all hybrids, having a combination of WW and ww genes, but the dominant trait (purple) expressed itself in the phenotype. Quick Tip: Mendel's experiments revealed that dominant traits, such as purple flowers, mask the expression of recessive traits, such as white flowers, in F\textsubscript{1} hybrid plants.

When the F\textsubscript{1 generation plants (all Ww) are crossed with each other, the F\textsubscript{2 generation shows the following results:

(i) Percentage of white flowered plants:

- White flowers occur in the F\textsubscript{2 generation when the genotype is ww. According to Mendel's ratio, 25 of the plants in the F\textsubscript{2 generation will have the white flower trait (ww).


(ii) Ratio of gene combinations WW, Ww, and ww in F\textsubscript{2 generation:

- The ratio of gene combinations in F\textsubscript{2 generation is 1:2:1. This means:

- 1 WW (homozygous dominant)

- 2 Ww (heterozygous)

- 1 ww (homozygous recessive)

Quick Tip: The Mendelian inheritance ratio of 1:2:1 in F\textsubscript{2} generation reflects the segregation of alleles during gamete formation and fertilization.

A dominant trait is one that expresses itself in the phenotype even when only one copy of the allele is present, whereas a recessive trait only expresses itself when both alleles are recessive (i.e., in the homozygous recessive state). Quick Tip: Dominant traits mask the expression of recessive traits in heterozygotes, while recessive traits are only visible when both alleles are recessive.

- To determine the focal length of the lens, we need to use the lens formula: \[ \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \]
Where \( f \) is the focal length, \( v \) is the image distance, and \( u \) is the object distance.

- From the table, we can observe that as the object distance (\( u \)) decreases, the image distance (\( v \)) increases.

- This behavior is characteristic of a converging (convex) lens and suggests that the object is placed outside the focal length, but the exact focal length can be deduced if specific values for \( u \) and \( v \) are considered. Given the data, the image moves further as the object distance decreases, which is consistent with a convex lens having a positive focal length. Quick Tip: In ray diagrams for convex lenses, light rays diverging from an object parallel to the optical axis are refracted through the focal point on the opposite side.

- Observation (2) shows an image distance of +20 cm for an object distance of -60 cm. This is not correct because the image formed by a convex lens should be at a larger distance when the object is placed farther away.


The correct relationship should show the image moving towards the focal point as the object distance decreases. Thus, observation (2) seems to be incorrect. Quick Tip: In ray diagrams for convex lenses, light rays diverging from an object parallel to the optical axis are refracted through the focal point on the opposite side.

- Let's consider observation (4), where the object distance is -30 cm and the image distance is +30 cm. The ray diagram for this situation is as follows:



This diagram shows that the image is formed at the same distance as the object from the lens but on the opposite side of the focal point, as expected for a convex lens. Quick Tip: In ray diagrams for convex lenses, light rays diverging from an object parallel to the optical axis are refracted through the focal point on the opposite side.

The person is suffering from hypermetropia (farsightedness), which is a defect of vision where distant objects are seen more clearly than near objects. This defect occurs when the eye is too short or the cornea has too little curvature, causing light to focus behind the retina. Convex lenses are used to correct this defect by converging light before it enters the eye. Quick Tip: For correcting hypermetropia, convex lenses are used, and their power is calculated as \( P = \frac{1}{f} \). A positive power indicates the use of convex lenses.

Two common causes of hypermetropia are:

1. F\textsubscript{2Shortened eyeballF\textsubscript{2: The eye's length from the cornea to the retina is too short, which prevents the image from being focused on the retina.

2. F\textsubscript{2Weak curvature of the cornea or lensF\textsubscript{2: If the cornea or lens is too flat, it cannot bend light rays sufficiently to bring them to focus on the retina. Quick Tip: For correcting hypermetropia, convex lenses are used, and their power is calculated as \( P = \frac{1}{f} \). A positive power indicates the use of convex lenses.

The power of a lens \( P \) is related to its focal length \( f \) by the formula: \[ P = \frac{1}{f} \]
where \( P \) is the power in diopters (D) and \( f \) is the focal length in meters.

Given that the power \( P = +2.0 \, D \), we can calculate the focal length: \[ f = \frac{1}{P} = \frac{1}{2.0} = 0.5 \, m \]


Thus, the focal length of the lenses used in the spectacles is 0.5 meters. Quick Tip: For correcting hypermetropia, convex lenses are used, and their power is calculated as \( P = \frac{1}{f} \). A positive power indicates the use of convex lenses.

The potential difference between two points is defined as the amount of work required to move a unit positive charge from one point to the other against the electric field. If the potential difference between two points is 1 volt, it means that 1 joule of work is done to move a charge of 1 coulomb from one point to another.

Mathematically, the potential difference \( V \) is given by: \[ V = \frac{W}{Q} \]


where \( W \) is the work done in joules and \( Q \) is the charge in coulombs.
Thus, a potential difference of 1 volt means 1 joule of energy is required to move 1 coulomb of charge between the two points. Quick Tip: The unit of potential difference is the volt, and 1 volt is the potential difference when 1 joule of energy is used to move 1 coulomb of charge.

(i) Symbol of a Battery (or Cell):
The symbol \( + \, - \) represents a simple electric cell or battery in a circuit.

- F\textsubscript{2Function:F\textsubscript{2 The function of a battery is to supply electrical energy to the circuit. It provides the voltage or potential difference that drives the current through the circuit.


(ii) Symbol of a Resistor:
The symbol \( \, \bigtriangleup \, \) represents a resistor in an electric circuit.

- F\textsubscript{2Function:F\textsubscript{2 The function of a resistor is to limit or control the flow of electric current in the circuit. It converts electrical energy into heat energy and helps in regulating the current in various parts of the circuit. Quick Tip: A battery provides the necessary potential difference to drive current, while resistors help control and limit the flow of current in the circuit.

- The alcohol with two carbon atoms is F\textsubscript{2ethanolF\textsubscript{2 (C\textsubscript{2H\textsubscript{5OH), and the carboxylic acid with two carbon atoms is F\textsubscript{2acetic acidF\textsubscript{2 (CH\textsubscript{3COOH).

F\textsubscript{2Ethanol Structure:F\textsubscript{2 \[ C_2H_5OH \]
In the presence of oxygen or acid, ethanol can be oxidized to acetic acid (CH\textsubscript{3COOH).

F\textsubscript{2Acetic acid Structure:F\textsubscript{2 \[ CH_3COOH \]

F\textsubscript{2Conversion of Ethanol to Acetic Acid:F\textsubscript{2
When ethanol is oxidized, it forms acetic acid. The reaction can be written as: \[ C_2H_5OH \xrightarrow{O_2} CH_3COOH \]
This is an oxidation reaction where ethanol (an alcohol) is converted to acetic acid (a carboxylic acid) by the addition of oxygen.

F\textsubscript{2Reaction of Ethanol and Acetic Acid in the Presence of Acid:F\textsubscript{2
When ethanol and acetic acid react in the presence of an acid (e.g., concentrated H\textsubscript{2SO\textsubscript{4), they undergo F\textsubscript{2esterificationF\textsubscript{2 to form F\textsubscript{2ethyl acetateF\textsubscript{2 (an ester) and water. The chemical equation for this reaction is: \[ C_2H_5OH + CH_3COOH \xrightarrow{H_2SO_4} CH_3COOC_2H_5 + H_2O \]
In this reaction, F\textsubscript{2ethyl acetateF\textsubscript{2 is formed along with water. Quick Tip: Esterification is a reversible reaction in which an alcohol and a carboxylic acid react in the presence of a catalyst (usually an acid) to form an ester and water.

- F\textsubscript{2SoapsF\textsubscript{2 are sodium or potassium salts of fatty acids, which are long-chain carboxylic acids. They are used as cleaning agents because they can remove dirt and oils from surfaces.

F\textsubscript{2Structure of Soap Molecule:F\textsubscript{2
A soap molecule consists of a long hydrocarbon chain (non-polar) attached to a carboxylate group (polar). The general formula for soap is: \[ RCOONa \]
Where R is a long hydrocarbon chain .

F\textsubscript{2Cleansing Action of Soap:F\textsubscript{2
Soap molecules have two parts:

- The F\textsubscript{2hydrophobic tailF\textsubscript{2 (non-polar) which is attracted to oils and grease.

- The F\textsubscript{2hydrophilic headF\textsubscript{2 (polar) which is attracted to water.

When soap is added to water, the hydrophobic tail attaches to the grease or dirt, while the hydrophilic head faces outward, forming F\textsubscript{2micellesF\textsubscript{2. The soap molecules surround the dirt or oil, allowing it to be removed by water.

F\textsubscript{2Soaps in Hard Water:F\textsubscript{2
In hard water, soap reacts with calcium (Ca) or magnesium (Mg) ions present in the water to form F\textsubscript{2insoluble scumF\textsubscript{2, which makes the soap less effective. This is why soap is not considered suitable for washing clothes in regions with hard water.

F\textsubscript{2Overcoming Hard Water Problem:F\textsubscript{2
To overcome this problem, water softeners (like washing soda, Na\textsubscript{2CO\textsubscript{3) can be used to remove calcium and magnesium ions from water. Washing soda reacts with Ca and Mg ions to form insoluble carbonates, thereby softening the water and allowing soap to work effectively. Quick Tip: The ability of soap to emulsify oils and dirt makes it an effective cleaning agent, but hard water reduces its cleaning efficiency by forming scum.

F\textsubscript{2PubertyF\textsubscript{2 is the period of life when an individual becomes capable of sexual reproduction. It involves a series of physical, hormonal, and emotional changes that prepare the body for reproductive capability.

Two changes seen in boys at the time of puberty include:

1. F\textsubscript{2Development of secondary sexual characteristics:F\textsubscript{2 This includes the growth of facial and body hair and deepening of the voice.

2. F\textsubscript{2Increase in height and muscle mass:F\textsubscript{2 Boys experience a growth spurt, and there is an increase in muscle development. Quick Tip: Puberty marks the transition from childhood to adulthood, characterized by changes in physical appearance and the ability to reproduce.

The testes are located outside the abdominal cavity in the scrotum to maintain a temperature lower than the body's core temperature, which is essential for the production of healthy sperm. Sperm production requires a temperature of around 2–3°C lower than the normal body temperature, and the scrotum helps regulate this temperature by contracting or relaxing in response to environmental conditions. Quick Tip: The scrotum's ability to regulate temperature helps ensure the optimal conditions for sperm production.

Three techniques of contraception used by humans include:

1. F\textsubscript{2CondomsF\textsubscript{2 (for both males and females).

2. F\textsubscript{2Oral contraceptivesF\textsubscript{2 (birth control pills) – typically used by females.

3. F\textsubscript{2Intrauterine device (IUD)F\textsubscript{2 – a device used by females to prevent pregnancy.


The technique that is F\textsubscript{2notF\textsubscript{2 meant for males is the F\textsubscript{2intrauterine device (IUD)F\textsubscript{2, as it is used in females to prevent pregnancy by being placed inside the uterus. Quick Tip: Contraceptive methods are essential for family planning and can be hormonal, barrier, or device-based, with options available for both males and females.

- F\textsubscript{2Production of eggsF\textsubscript{2: The F\textsubscript{2ovariesF\textsubscript{2 are the organs responsible for the production of eggs (ova).

- F\textsubscript{2Site of fertilizationF\textsubscript{2: Fertilization occurs in the F\textsubscript{2fallopian tubesF\textsubscript{2 (also called oviducts)
.
- F\textsubscript{2Site of implantationF\textsubscript{2: The fertilized egg implants in the F\textsubscript{2uterusF\textsubscript{2.

- F\textsubscript{2Entry of spermsF\textsubscript{2: The sperms enter the female reproductive system through the F\textsubscript{2vaginaF\textsubscript{2. Quick Tip: The female reproductive system involves the ovaries, fallopian tubes, uterus, and vagina, each playing a critical role in reproduction.

- F\textsubscript{2Subsequent to the implantation of the zygoteF\textsubscript{2: After the zygote implants in the uterine lining, the uterus thickens and remains prepared to support the pregnancy. Hormones such as progesterone maintain the uterine lining.

- F\textsubscript{2If an egg does not get fertilizedF\textsubscript{2: If fertilization does not occur, the uterus sheds its lining during menstruation, and the menstrual cycle continues. The egg is expelled from the body along with the uterine lining. Quick Tip: If fertilization does not occur, the body goes through the menstrual cycle to shed the unused egg and uterine lining.

F\textsubscript{2Magnetic Field LinesF\textsubscript{2: Magnetic field lines represent the direction and strength of a magnetic field. These lines emerge from the north pole and enter the south pole. The denser the field lines, the stronger the magnetic field at that point.

F\textsubscript{2Direction of Magnetic FieldF\textsubscript{2: The direction of the magnetic field at any point is determined by the F\textsubscript{2right-hand ruleF\textsubscript{2. If you curl the fingers of your right hand in the direction of the current in a wire, the direction of your thumb gives the direction of the magnetic field lines.

F\textsubscript{2Magnetic Field Due to a Current-Carrying Circular LoopF\textsubscript{2:
For a circular loop carrying a current, the magnetic field lines form concentric circles around the wire and they pass through the center of the loop. The magnetic field is strongest at the center of the loop and decreases as you move away from the center.
\[ Current: \, \rightarrow \, Clockwise or Counter-clockwise depending on the view. \] \[ Magnetic Field Lines: \, \rightarrow \, Form circular loops around the current. \]

F\textsubscript{2Factors Affecting the Magnitude of the Magnetic FieldF\textsubscript{2:
The magnitude of the magnetic field produced by a current-carrying coil depends on:
1. F\textsubscript{2Current (I)F\textsubscript{2: The greater the current, the stronger the magnetic field.
2. F\textsubscript{2Number of turns (N)F\textsubscript{2: More turns in the coil result in a stronger magnetic field. Quick Tip: The magnetic field around a current-carrying wire can be visualized using the right-hand rule, where your thumb points in the direction of the current and the curl of your fingers shows the magnetic field direction.

F\textsubscript{2Why can’t Two Magnetic Field Lines Cross Each Other?F\textsubscript{2
If two magnetic field lines were to cross each other, it would imply that the magnetic field has two different directions at the same point, which is not possible. Therefore, magnetic field lines never intersect.

F\textsubscript{2Magnetic Field Due to a Current-Carrying Long Straight SolenoidF\textsubscript{2:
A solenoid is a coil of wire carrying a current. The magnetic field produced by a solenoid is uniform and parallel inside the solenoid, with the field lines forming straight lines from one end to the other. Outside the solenoid, the field lines are similar to the field of a bar magnet, with distinct north and south poles.
\[ Inside the solenoid: \, Uniform magnetic field, parallel lines. \] \[ Outside the solenoid: \, Similar to a bar magnet's field, with loops. \]

F\textsubscript{2Conclusion from Magnetic Field Lines of a SolenoidF\textsubscript{2:
The magnetic field inside the solenoid is uniform and parallel, and its strength depends on the current in the solenoid and the number of turns per unit length. Quick Tip: A solenoid produces a uniform magnetic field inside, making it useful as a magnet in various applications. The strength of the magnetic field can be increased by increasing the number of turns or the current.

When a metal is converted to an alloy by mixing a small amount of a different element, several physical properties of the metal change. For example:

- F\textsubscript{2Electrical ConductivityF\textsubscript{2: The electrical conductivity of a metal typically decreases when it is turned into an alloy. This happens because the atoms of the added element create irregularities in the atomic structure, which disrupt the free flow of electrons necessary for conduction.

- F\textsubscript{2Melting PointF\textsubscript{2: The melting point of an alloy often differs from the melting points of the constituent metals. Typically, alloys have a F\textsubscript{2lower melting pointF\textsubscript{2 than their pure components, especially if the alloy formation creates a new crystalline structure that requires less energy to break. Quick Tip: Alloys are often used to improve the properties of metals for specific applications, such as increased strength or better corrosion resistance, which cannot be achieved by pure metals alone.

F\textsubscript{2AlloysF\textsubscript{2 are mixtures of two or more metals or a metal and a non-metal. The properties of alloys differ from those of pure metals, making them useful for various applications. Alloys are typically created by melting the metals together.

F\textsubscript{2BrassF\textsubscript{2 is an alloy primarily composed of:

- F\textsubscript{2Copper (Cu)F\textsubscript{2: 70-90

- F\textsubscript{2Zinc (Zn)F\textsubscript{2: 10-30


Brass is prepared by melting copper and zinc together. It is widely used for making instruments, coins, and decorative items due to its corrosion resistance and aesthetic qualities. Quick Tip: Brass is known for its high durability and excellent workability, making it ideal for applications that require both strength and resistance to corrosion.

F\textsubscript{2Stainless SteelF\textsubscript{2 is a corrosion-resistant alloy made primarily of:

- F\textsubscript{2Iron (Fe)F\textsubscript{2: 70-90

- F\textsubscript{2Chromium (Cr)F\textsubscript{2: 10-20

- F\textsubscript{2Nickel (Ni)F\textsubscript{2: 5-10


Stainless steel is prepared by adding chromium and nickel to steel, which enhances its corrosion resistance, especially to rust and staining. It is widely used in cooking utensils and other kitchenware due to its non-reactive nature with food and its high durability.


F\textsubscript{2Important PropertyF\textsubscript{2:
The presence of chromium in stainless steel forms a thin, self-healing layer of chromium oxide on the surface, making it resistant to corrosion and stains. This property makes it much more suitable than pure iron for cooking utensils. Quick Tip: Stainless steel’s ability to resist rust and maintain its strength under high heat is why it is the preferred material for cooking utensils.

- The movement which causes F\textsubscript{2‘X’F\textsubscript{2 (roots) to grow downwards is called F\textsubscript{2gravitropismF\textsubscript{2 (also known as geotropism), where the plant grows in response to gravity.

- The movement which causes F\textsubscript{2‘Y’F\textsubscript{2 (stem) to grow upwards is called F\textsubscript{2negative gravitropismF\textsubscript{2 (also known as geotropism), where the plant grows against gravity. Quick Tip: Gravitropism is a crucial response for plants to orient their roots downward into the soil for water and nutrients, while the stem grows upward toward light for photosynthesis.

- (i) The hormone that plays a major role in F\textsubscript{2falling of leavesF\textsubscript{2 is F\textsubscript{2Abscisic acid (ABA)F\textsubscript{2. ABA promotes leaf abscission, particularly under stress conditions such as drought.

- (ii) The hormone that plays a major role in F\textsubscript{2rapid cell divisionF\textsubscript{2 is F\textsubscript{2CytokininsF\textsubscript{2. Cytokinins promote cell division and are often found in areas of active growth. Quick Tip: Abscisic acid helps in maintaining plant water balance, while cytokinins are key regulators in stimulating plant cell division.

The F\textsubscript{2sensitive plant (Mimosa pudica)F\textsubscript{2 exhibits F\textsubscript{2thigmotropismF\textsubscript{2, which is the movement in response to touch.
- When the leaves of the sensitive plant are touched, it causes a rapid change in turgor pressure in the cells.
- The signal is first detected by mechanoreceptors in the plant's cells, which then trigger an electrical impulse that moves across the plant tissue.
- This causes a change in the flow of water in the plant cells, resulting in the leaves folding and drooping. This is a defense mechanism to avoid herbivory. Quick Tip: Thigmotropism helps plants respond to physical stimuli, and this unique movement is powered by changes in water pressure inside plant cells.

The plant hormone synthesized at the shoot tip is F\textsubscript{2AuxinF\textsubscript{2.

- F\textsubscript{2AuxinsF\textsubscript{2 promote cell elongation on the side of the plant that is away from the light, causing the plant to bend toward the light source.

- This phenomenon is known as F\textsubscript{2phototropismF\textsubscript{2, where the plant grows towards light to maximize photosynthesis. Quick Tip: Auxin helps plants adapt to their environment by guiding their growth towards essential resources like light and water.

In this case, we would rearrange the resistors into a parallel combination and ensure the same battery is connected along with the ammeter and voltmeter. The circuit diagram for the parallel combination is shown below:

In a F2parallel combinationF2, the F2potential differenceF2 across each resistor is the same. Therefore, the potential difference across X and Y will be the same in parallel.

However, in F2series combinationF2, the current through both resistors will be the same as the same current flows through all components in a series circuit. Thus, the correct combination is the F2parallel combinationF2 for the potential difference and the F2series combinationF2 for the current.

In a series combination, the total resistance \(R_{total}\) is the sum of the individual resistances: \[ R_{total} = R_X + R_Y = 3 \, \Omega + 6 \, \Omega = 9 \, \Omega \]

Using Ohm's law \(I = \frac{V}{R}\), where \(V = 2V\) and \(R_{total} = 9 \, \Omega\), we find the current \(I\) as: \[ I = \frac{2V}{9 \, \Omega} = 0.222 \, A \]

Thus, the current drawn from the battery is \(0.222 \, A\). Quick Tip: In a series circuit, the current remains the same throughout, but in a parallel circuit, the potential difference across each component is identical.

In a parallel combination, the reciprocal of the total resistance \(R_{total}\) is the sum of the reciprocals of the individual resistances: \[ \frac{1}{R_{total}} = \frac{1}{R_X} + \frac{1}{R_Y} = \frac{1}{3 \, \Omega} + \frac{1}{6 \, \Omega} \] \[ \frac{1}{R_{total}} = \frac{2}{6} + \frac{1}{6} = \frac{3}{6} \] \[ R_{total} = \frac{6}{3} = 2 \, \Omega \]

Thus, the equivalent resistance of the parallel combination of the two resistors is \(2 \, \Omega\). Quick Tip: In a parallel circuit, the total resistance decreases as more resistors are added. The reciprocal of the total resistance is the sum of the reciprocals of individual resistances.