JKBOSE Solved Model Question Paper for Class X Science Theory (2023) 

Solved Model Question Paper for Class X Science Theory (2023)

Max. Marks: 80 

                                              Section – A 

Question 1: What is dioptre? 

Answer: A dioptre is a unit of measurement of the refractive power of a lens. It is a unit of measurement of the refractive power of a lens, equal to the reciprocal of the focal length measured in metres.

It is used to measure the strength of corrective lenses such as eyeglasses, contact lenses, and intraocular lenses.

Question 2: Give any one point of difference between a concave lens and a convex lens. 

Answer: A concave lens has its curved surface facing inward (toward the light source) and a convex lens has its curved surface facing outward (away from the light source).

Question 3: A person is wearing spectacles with a concave lens of suitable focal length. What kind of defect of vision is he having? 

a. Myopia 

b. Hypermetropia 

c. Presbyopia 

d. Both b & c 

Answer: a. Myopia

Question 4: In electric fittings, we mostly use copper wires. Why? 

Answer: Copper is the most widely used conductor in electrical wiring due to its excellent electrical and thermal conductivity, corrosion resistance, and ductility. Copper wires are more malleable than other metals, making them easier to work with and shape. Copper is also more cost-effective than other materials, making it a popular choice for electrical fittings.

Question 5: In presence of sunlight, silver chloride decomposes to give silver and chlorine gas. Write a balanced chemical equation for it. 

Answer: AgCl (s) → Ag (s) + Cl2 (g)

Question 6: Which of the following processes involve chemical reactions? 

a. Storing of oxygen gas under pressure in a gas cylinder 

b. Liquefaction of air 

c. Keeping petrol in a china dish in the open 

d. Heating copper wire in presence of air at high temperature 

Answer: b. Liquefaction of air,

Q.7: Draw the electron dot structure for the ammonia molecule. 

Ans: The electron dot structure for the ammonia molecule is shown below:

              NH₃ : ,  :N: · · · , :H: · · · ·

Question 8:Write the structural formula of Cyclohexane. 

Answer: The structural formula of Cyclohexane is shown below:

Answer : [CH2]6

Question 9: Arrange the following metals in the order of their increasing reactivity. Copper, Aluminium, Silver, Zinc, Iron 

Answer: Copper, Zinc, Iron, Aluminium, Silver

Question 10: Which one of the following four metals would be displaced from the solution of its salts by the other three metals? 

a. Magnesium 

b. Silver 

c. Zinc 

d. Copper 

Answer: Silver

Question 11: Name any four common waste disposal methods. 

Answer: 1. Recycling 2. Composting 3. Incineration 4. Landfilling

                                 Section – B 

Question 12: State any two practices which can help in the protection of our environment. 

Answer: 1. Reduce, Reuse, Recycle: Waste reduction, reuse of materials, and recycling of materials are some of the most effective ways of protecting the environment.

2. Plant Trees: Planting trees is one of the most effective ways of improving air quality, reducing soil erosion, and providing habitats for wildlife.

Question 13: What do you mean by Global warming? 

Answer: Global warming is the gradual increase in the overall temperature of the Earth’s atmosphere due to the increase in certain pollutants such as carbon dioxide, methane, and other greenhouse gases. As global temperatures rise, the effects of climate change become more pronounced, leading to extreme weather events such as droughts, floods, and hurricanes, as well as rising sea levels.

Question 14: What is the basic cause of atmospheric refraction? 

Answer: The basic cause of atmospheric refraction is the changing atmospheric density with altitude. As light travels through the atmosphere, it is bent, or refracted, by different layers of air with varying densities.

Question 15: Mention any two functions of the human ovary. 

Answer: The two functions of the human ovary are:

1. Production of hormones: The ovary produces the hormones estrogen and progesterone which play an important role in the menstrual cycle and fertility.

2. Production of ova: The ovary also produces ova or eggs which are released during ovulation. These ova are essential for reproduction.

Question 16: What is the importance of DNA copying in reproduction? 

Answer: DNA copying is essential for reproduction because it ensures that the genetic information of the parent is passed on to the offspring. During reproduction, the parent’s DNA is passed on to the offspring through DNA copying. If the DNA is not accurately copied, the offspring will have genetic mutations which can lead to a variety of diseases. DNA copying is also important for maintaining genetic diversity and allowing organisms to adapt to their environment over time.

Question 18: What is the function of blood capillaries surrounding the nephron? 

Answer: Blood capillaries surrounding the nephron are responsible for transporting waste and other materials from the nephron to the bloodstream and for absorbing nutrients from the bloodstream and returning them to the nephron.

They also provide the nephron with oxygen and other nutrients necessary for its functioning.

                                        Section – C 

Question 19: What are the advantages of sexual reproduction over asexual reproduction? 

Answer: Advantages of sexual reproduction over asexual reproduction include the following:

1. Increased genetic diversity due to the mixing of genetic material from two parents, which can lead to a greater adaptation to changing environments.

2. Greater opportunity for natural selection, as the offspring produced have different combinations of genes, some of which may be beneficial in certain environments.

3. Increased ability to ward off disease, as the offspring produced have a greater variety of immune systems.

4. A greater chance of survival in times of environmental stress and change, as the offspring produced are more likely to have the appropriate traits to survive.

5. The potential for evolution and species diversification, as different combinations of genes, may lead to the development of new species.

Question 20: Differentiate between self-pollination and cross-pollination. 

Answer: Self-pollination is the process of pollination in which the pollen from the same flower or another flower on the same plant is transferred to the pistil to produce seeds. Cross-pollination is the process of pollination in which the pollen from one plant is transferred to the pistil of another plant to produce seeds.

Question 21: Show XX-XY type of sex determination in human beings through a diagram. 

Answer: In humans, XX-XY type of sex determination is the most common type of sex determination. This is based on the presence of two sex chromosomes, X and Y. Females possess two X chromosomes (XX), while males possess one X chromosome and one Y chromosome (XY).

Whether a child will be a girl or a boy is determined by the genes they get from their parents. Humans have two sex chromosomes, the X and Y chromosomes; males contribute XY chromosomes and females contribute XY chromosomes. A daughter will be born if an X-chromosome-carrying sperm fertilises an X-chromosome-carrying ovum. A boy will be born if a sperm with the Y chromosome mates with an egg with the X chromosome.

Question 22: Give any three applications of the heating effect of electric current. 

Answer: 1. Electric heating elements are used in coffee makers, toasters, and hot water tanks.

2. Electric ovens and stoves use electric heating elements to cook food.

3. Electric heating elements are used in soldering irons to melt metal for welding.

Question 23: Give advantages of hydel power plants over thermal power plants. 

Answer: Advantages of hydel power plants over thermal power plants:

1. Hydel power plants are much cheaper to build, operate, and maintain than thermal power plants.

 2. Hydel power plants require very little fuel, therefore reducing air pollution and other environmental impacts.

3. Hydel power plants have a much longer lifespan than thermal power plants, sometimes up to 50 years.

4. Hydel power plants can generate electricity on demand, making them highly efficient.

5. Hydel power plants can produce electricity in remote locations, providing access to electricity in rural areas.

6. Hydel power plants can be used to generate electricity during peak times, helping to reduce electricity costs.

Question 24: When we keep silver bromide in sunlight for some time, it is observed that yellow silver bromide turns grey. What type of chemical reaction is this? Write down a balanced chemical equation for the said reaction. 

Answer: This is a photolytic reaction.

AgBr (s) + hv → Ag (s) + Br2 (g)

Question 25: Describe briefly the electrolytic refining of copper. 

Answer: Electrolytic refining of copper is the process of purifying copper through the use of electricity. During this process, impurities are removed from the copper anode by transferring them to the cathode, which consists of a pure copper sheet. The anode is placed in an electrolyte solution, and a direct current of electricity is passed through the solution. This causes the impurities to be attracted to the cathode and to be discharged as sludge, while the pure copper is deposited on the cathode. The resulting copper is of a much higher purity than the starting material.

Question 26: What do you mean by apical dominance? Name the hormone that controls it.

Answer: Apical dominance is a phenomenon in which the main stem of a plant dominates its lateral branches. The hormone that controls apical dominance is auxin. 

                                      Section – D 

Question 27: With the help of a ray diagram, explain the following terms: 

i. Principal focus of a concave mirror 

ii. Principal focus of a convex mirror 

iii. Centre of curvature

Answer: i. The principal focus of a concave mirror is the point where all incident parallel rays converge to a single point after reflection from the mirror.

ii. The principal focus of a convex mirror is the point from which all reflected rays appear to diverge.

iii. The centre of curvature of a mirror is the point that lies at the centre of the curvature of the mirror.

Question 28: The focal length of a concave lens is 20cm. At what distance from the lens a 5cm tall object be placed so that it will form an image at 15 cm from the lens? Also, calculate the size of the image formed. 

Question 29: Explain the following with examples: 

i. Addition reactions 

ii. Combustion reactions 

iii. Substitution reactions 

Answer: i. Addition reactions: Addition reactions are chemical reactions in which two or more molecules combine to form a larger molecule. Examples of addition reactions include the addition of halogens to alkanes, such as the reaction of chlorine with propane to form chloropropane.

ii. Combustion reactions: Combustion reactions are chemical reactions in which a fuel reacts with oxygen to produce heat and light. Examples of combustion reactions include the burning of gasoline in an automobile engine and the burning of natural gas in a furnace.

iii. Substitution reactions: Substitution reactions are chemical reactions in which one molecule replaces another in a molecule or a reaction. Examples of substitution reactions include the substitution of one functional group for another in a molecule, such as the substitution of a hydroxyl group for a chlorine atom in alcohol, or the substitution of one reactant for another in a reaction, such as the substitution of ethanol for methanol in a reaction.

Question 30: What is heterotrophic nutrition? Explain different types of heterotrophic nutrition. 

Answer: Heterotrophic nutrition is a type of nutrition in which organisms obtain their food from other living organisms. This type of nutrition is seen in most animals and some fungi and protists. The different types of heterotrophic nutrition are as follows:

1. Herbivory: Herbivores are organisms that feed on plants. Examples of herbivores include cows, goats, rabbits, and deer.

2. Carnivory: Carnivores are organisms that feed on other animals. Examples of carnivores include lions, tigers, wolves, and sharks.

3. Parasitism: Parasitism is a type of symbiotic relationship in which one organism (the parasite) feeds off of another organism (the host). Examples of parasites include fleas, ticks, and tapeworms.

4. Saprophytism: Saprophytes are organisms that feed on dead or decaying organic matter. Examples of saprophytes include mushrooms and certain bacteria.

5. Detritivory: Detritivores are organisms that feed on inorganic material such as dust, soil, and dead leaves. Examples of detritivores include earthworms and certain insects.

Question 31: Describe the process of transportation of water and food in plants. 

Answer: The process of transportation of water and food in plants is called translocation. It is a process in which water, minerals, and organic compounds are transported through the plant’s vascular system. Water and minerals are absorbed by the plant’s root system and transported up to the leaves and other parts of the plant. Organic compounds, such as sugars and amino acids, are synthesized in the leaves and then transported throughout the plant. The movement of water and nutrients is accomplished through the xylem, while the movement of organic compounds is accomplished through the phloem. The xylem is a system of tubes that transport water from the roots to the leaves, while the phloem is a system of tubes that transport organic compounds throughout the plant.

Question 33: What is the value of the refractive index for water and a crown glass? 

Answer: Refractive index for water = 1.333

The refractive index for crown glass = 1.517

Question 34: Draw a flow chart depicting a reflex action. 

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