Karnataka SSLC 2022 Main Exam Science (83-E) Question Paper with Step-by-Step Solutions

1. Recall that the power of a lens is defined as the reciprocal of its focal length.
2. Identify the SI unit of focal length as the metre (m).
3. Determine that the SI unit of power is the reciprocal of the metre, which is the dioptre (D).

Answer: Dioptre (D)

1. Draw one closed rectangular loop of connecting wire (a series circuit: no branches).
2. On one side draw the cell: a long thin line (+) and a short thick line (−).
3. Put the bulb symbol (a circle with a cross) on another side and the ammeter (a circle with A, + terminal towards the cell's +) on a third side.
4. On the fourth side draw the plug key: ( • ) when closed or ( ) when open.

Answer: A single loop with cell, bulb, ammeter and plug key all in series.

1. Given: Object distance u = -25 cm, Focal length f = -15 cm.
2. Using the mirror formula: 1/v + 1/u = 1/f.
3. Substitute values: 1/v + 1/(-25) = 1/(-15).
4. Rearrange: 1/v = -1/15 + 1/25.
5. Find common denominator (75): 1/v = (-5 + 3)/75 = -2/75.
6. Solve for v: v = -75/2 = -37.5 cm.

Answer: The screen should be placed 37.5 cm in front of the mirror.

1. Given: Focal length (f) = -15 cm (negative for concave lens), Image distance (v) = -10 cm (negative as image is virtual and on the same side).
2. Use the lens formula: 1/f = 1/v - 1/u.
3. Substitute the values: 1/(-15) = 1/(-10) - 1/u.
4. Rearrange to solve for 1/u: 1/u = 1/(-10) - 1/(-15).
5. Simplify the right side: 1/u = -1/10 + 1/15.
6. Find a common denominator (30): 1/u = -3/30 + 2/30.
7. Calculate the result: 1/u = -1/30.
8. Solve for u: u = -30 cm.

Answer: The object must be placed 30 cm from the lens on the same side as the incident light.

1. Identify the major component of biogas as methane (CH₄).
2. List the first quality: It should be renewable or have a large reserve.
3. List the second quality: It should be easy to transport and store.
4. List the third quality: It should be economical and produce less pollution.
5. List the fourth quality: It should be efficient and have a high energy output per unit mass.

Answer: The major component of biogas is methane (CH₄). Four qualities of a good source of energy are: it should be renewable, easy to transport and store, economical with low pollution, and efficient.

1. Identify the element: Silicon is the primary element used to make solar cells.
2. List Advantage 1: Solar cells are pollution-free and do not produce greenhouse gases during operation.
3. List Advantage 2: They have no moving parts, which means there is no wear and tear and low maintenance cost.
4. List Advantage 3: Solar energy is a renewable source that is available in abundance and does not deplete.
5. List Advantage 4: Solar cells can be installed in remote areas where grid electricity is not available.

Answer: Silicon is used to make solar cells. Advantages: Pollution-free, no moving parts (low maintenance), renewable, and usable in remote areas.

1. Draw the principal axis and the convex lens; mark O, F₁, 2F₁ on the left and F₂, 2F₂ on the right.
2. Draw the object AB upright at 2F₁.
3. Ray 1: from A parallel to the axis; after refraction it passes through F₂.
4. Ray 2: from A through the optical centre O; it goes straight on.
5. The two refracted rays meet below the axis, exactly above/below 2F₂: that point is A′. Draw the image A′B′ from the axis at 2F₂ down to A′.

Answer: The image is at 2F₂, on the other side of the lens; it is real, inverted and the same size as the object.

1. An earth wire provides a low-resistance path to the ground for any leakage current that may flow through the metal body of an appliance.
2. If the live wire touches the metal body due to insulation failure, the current flows through the earth wire instead of through a person touching the appliance.
3. This causes a large current to flow, which trips the fuse or circuit breaker, cutting off the supply and preventing electric shock.

Answer: The earth wire protects against electric shock by providing a safe path for leakage current to flow to the ground, ensuring the metal body does not become live.

1. Faraday's Experiment: Place a coil connected to a galvanometer near a strong bar magnet. When the magnet is moved towards or away from the coil, the galvanometer needle deflects momentarily, indicating an induced current. When the magnet is stationary, the needle returns to zero. This shows that a changing magnetic field induces current in a conductor.
2. Direct Current (DC): It is a current that flows in only one direction and does not change its magnitude or direction with time. Example: Current from a dry cell or battery.
3. Alternating Current (AC): It is a current that changes its direction and magnitude periodically with time. It reverses direction after a fixed interval called the time period. Example: Current supplied by power stations.

Answer: Faraday's experiment demonstrates that a changing magnetic field induces an electric current in a coil. DC flows in one direction, while AC changes direction and magnitude periodically.

1. (a) 1. In parallel every device gets the full supply voltage, so each works at its rated power.
2. 2. If one device fails or is switched off, the others keep working.
3. 3. Each device can have its own switch and draw only the current it needs.
4. (b) An ammeter is connected in series with the part of the circuit; it measures the electric current (in ampere).
5. A voltmeter is connected in parallel across the component; it measures the potential difference across it (in volt).

Answer: Parallel connection ensures constant voltage and independent operation of devices. Ammeter is connected in series to measure current; voltmeter is connected in parallel to measure potential difference.

1. (a) Refraction is the bending of light when it passes from one transparent medium to another due to a change in its speed.
2. The two laws of refraction are: 1. The incident ray, the refracted ray, and the normal to the interface at the point of incidence all lie in the same plane. 2. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media and a given colour of light (Snell's Law).
3. (b) Refractive index (n) is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v). Formula: n = c / v.
4. It can also be defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction: n = sin(i) / sin(r).
5. 'The refractive index of diamond is 2.42' means that the speed of light in diamond is 1/2.42 times the speed of light in vacuum, or equivalently, light travels 2.42 times slower in diamond than in vacuum.

Answer: Refraction is the bending of light due to change in speed. Laws: 1. Incident, refracted ray and normal are coplanar. 2. sin(i)/sin(r) is constant. Refractive index is the ratio of speed of light in vacuum to speed in medium. Diamond's n=2.42 means light travels 2.42 times slower in diamond than in vacuum.

1. Recall the products of electrolysis of water: hydrogen and oxygen.
2. Identify that hydrogen gas is produced at the cathode (negative electrode).
3. Identify that oxygen gas is produced at the anode (positive electrode).
4. Select the option corresponding to hydrogen.

Answer: Hydrogen — option (B).

1. Write the electronic configuration of Chlorine (atomic number 17) as 2, 8, 7.
2. Count the number of occupied shells, which is 3.
3. The number of occupied shells equals the period number, so Chlorine is in Period 3.

Answer: Period 3 (electronic configuration 2, 8, 7: three shells) — option (D).

1. Recall the definition of the modern periodic law.
2. State that the physical and chemical properties of elements are periodic functions of their atomic numbers.

Answer: The modern periodic law states that the physical and chemical properties of elements are periodic functions of their atomic numbers.

1. Write down the first use: Plaster of Paris is used to set fractured bones in the correct position.
2. Write down the second use: It is used to make toys, decorative items, and ornamental designs.

Answer: 1. To set fractured bones. 2. To make toys and decorative items.

1. Write the molecular formula C₂H₄.
2. Draw two carbon atoms joined by a double bond (C=C).
3. Attach two hydrogen atoms to each carbon atom with single bonds.

Answer: H₂C=CH₂

1. Identify the reactants: Zinc oxide (ZnO) and Carbon (C).
2. Oxidation is the gain of oxygen or loss of hydrogen. Carbon (C) gains oxygen to form Carbon monoxide (CO), so Carbon is oxidised.
3. Reduction is the loss of oxygen or gain of hydrogen. Zinc oxide (ZnO) loses oxygen to form Zinc (Zn), so Zinc oxide is reduced.

Answer: Carbon is oxidised and Zinc oxide is reduced.

1. Recall that the pH scale ranges from 0 to 14, where values below 7 indicate acidity.
2. Identify that a lower pH value corresponds to a higher concentration of hydrogen ions (H⁺).
3. Compare the given pH values: 5 is lower than 6, and 6 is lower than 7.
4. Conclude that Solution A (pH 5) has the highest H⁺ concentration and is therefore the most acidic.

Answer: Solution A is the most acidic because it has the lowest pH value (5), indicating the highest concentration of hydrogen ions.

1. Take a beaker and pour the salt solution into it.
2. Take two graphite rods and insert them into the solution, ensuring they do not touch each other.
3. Connect the two graphite rods to a battery (cell) and a bulb (or LED) using connecting wires to form a complete circuit.
4. Observe whether the bulb glows or the LED lights up, indicating the conduction of electricity.

Answer: The set-up consists of a beaker with salt solution, two graphite rods inserted in it, and a circuit connecting the rods to a battery and a bulb. The bulb glows, showing that the salt solution conducts electricity.

1. (a) Metals are used for cooking vessels because they are good conductors of heat, allowing food to cook evenly, and they have high melting points so they do not melt at cooking temperatures.
2. (b) Sodium is stored in kerosene because it is highly reactive with moisture and oxygen in the air; kerosene acts as a barrier to prevent it from reacting spontaneously or catching fire.

Answer: (a) Good thermal conductivity and high melting point. (b) Prevents reaction with air/moisture due to high reactivity.

1. (a) Calcium reacts with water to produce hydrogen gas and calcium hydroxide. The reaction is exothermic but not vigorous enough to release sufficient heat to ignite the hydrogen gas, unlike sodium or potassium.
2. (b) Ionic compounds consist of ions arranged in a regular lattice structure held together by strong electrostatic forces of attraction between oppositely charged ions. A large amount of heat energy is required to overcome these strong forces, resulting in high melting and boiling points.

Answer: (a) The reaction of calcium with water is not vigorous enough to heat the hydrogen gas to its ignition temperature. (b) Strong electrostatic forces of attraction between oppositely charged ions in the lattice require a large amount of energy to break.

1. Atomic size is defined as the distance between the nucleus of an atom and the outermost shell of electrons.
2. It decreases across a period because the number of protons in the nucleus increases, leading to a greater effective nuclear charge that pulls the electrons closer to the nucleus.
3. It increases down a group because the number of electron shells increases, which places the outermost electrons further away from the nucleus despite the increase in nuclear charge.

Answer: Atomic size is the distance between the nucleus and the outermost shell. It decreases across a period due to increased nuclear charge and increases down a group due to the addition of new electron shells.

1. Draw a test tube on a stand with a few zinc granules and dilute sulphuric acid in it.
2. Close the mouth with a cork carrying a bent delivery tube.
3. Dip the other end of the delivery tube in soap solution in a small trough, so the gas forms soap bubbles.
4. Draw a burning candle brought near a gas-filled bubble: the gas burns with a pop sound, showing it is hydrogen.
5. Label 'zinc granules' (in the test tube) and 'delivery tube'.

Answer: Zinc + dilute H₂SO₄ in a test tube → delivery tube into soap solution → bubbles burn with a pop when a candle is brought near: hydrogen.

1. (i) Write the reactant calcium carbonate (CaCO₃) and the products calcium oxide (CaO) and carbon dioxide (CO₂).
2. (i) Balance the equation: CaCO₃ → CaO + CO₂. The atoms of Ca, C, and O are already equal on both sides (1:1:3), so the equation is balanced.
3. (ii) Write the reactants hydrogen (H₂) and chlorine (Cl₂) and the product hydrogen chloride (HCl).
4. (ii) Balance the equation: H₂ + Cl₂ → 2HCl. There are 2 H and 2 Cl atoms on the left, so place a coefficient of 2 before HCl on the right to balance the atoms.
5. (iii) Write the reactants magnesium (Mg) and hydrochloric acid (HCl) and the products magnesium chloride (MgCl₂) and hydrogen (H₂).
6. (iii) Balance the equation: Mg + 2HCl → MgCl₂ + H₂. There are 2 Cl atoms in MgCl₂, so place a coefficient of 2 before HCl on the left to balance Cl and H atoms.

Answer: (i) CaCO₃ → CaO + CO₂ (ii) H₂ + Cl₂ → 2HCl (iii) Mg + 2HCl → MgCl₂ + H₂

1. Type of reaction: Displacement reaction.
2. Reason: Iron is more reactive than copper, so it displaces copper from the copper sulphate solution.
3. Balanced equation: Fe + CuSO₄ → FeSO₄ + Cu.

Answer: It is a displacement reaction because iron displaces copper. The balanced equation is Fe + CuSO₄ → FeSO₄ + Cu.

1. (a) Structural isomers are compounds that have the same molecular formula but different structural formulae (different arrangement of atoms).
2. Molecular formula of butane: C₄H₁₀.
3. Structural formula of butane: CH₃–CH₂–CH₂–CH₃.
4. (b) Catenation is the unique ability of carbon atoms to form bonds with other carbon atoms to form long chains or rings.
5. The general formula of alkenes is CₙH₂ₙ.

Answer: Structural isomers have same molecular but different structural formulae; Butane is C₄H₁₀ (CH₃–CH₂–CH₂–CH₃). Catenation is carbon's ability to form chains; Alkenes follow CₙH₂ₙ.

1. Identify the layer of the atmosphere that protects life from harmful solar radiation.
2. Recall that the ozone layer, located in the stratosphere, absorbs the majority of the sun's ultraviolet (UV) rays.
3. Identify the chemical formula of ozone, which is O₃.

Answer: O₃ — option (C).

1. Identify the causative agent for each option: AIDS is caused by the Human Immunodeficiency Virus (HIV), Syphilis is caused by the bacterium Treponema pallidum, Tuberculosis is caused by the bacterium Mycobacterium tuberculosis, and Gonorrhoea is caused by the bacterium Neisseria gonorrhoeae.
2. Select the disease caused by a virus from the list.

Answer: AIDS — option (A).

1. Decomposers break down dead and decaying organic matter into simple inorganic substances.
2. These inorganic substances are returned to the soil, water, and air.
3. They act as a recycling mechanism for nutrients, making them available for producers to use again.

Answer: Decomposers recycle nutrients by breaking down dead organic matter into simple inorganic substances that return to the environment.

1. Testes need a temperature slightly lower than the body temperature for the formation of sperm.
2. The scrotum acts as a sac that keeps the testes outside the abdomen to maintain this lower temperature.

Answer: Testes are located outside the abdomen in the scrotum to maintain a temperature slightly lower than the body temperature, which is required for the formation of sperm.

1. Auxin: made at the shoot tip; it makes cells grow longer (cell elongation) and helps the shoot bend towards light (phototropism).
2. Cytokinin: promotes cell division; it is found in large amounts where cells divide fast, such as in fruits and seeds.

Answer: Auxin — cell elongation and bending towards light; cytokinin — cell division.

1. Draw a vertical line down the center of a flower to represent the longitudinal section.
2. Draw the outermost layer as sepals and the next layer as petals.
3. Draw the stamens (male part) consisting of anther and filament on the sides.
4. Draw the central pistil (female part) with a swollen base (ovary), a stalk (style), and a sticky top (stigma).
5. Label the swollen base of the pistil as 'Ovary'.

Answer: The ovary is the swollen base of the pistil which contains ovules.

1. (a) The ventricles have thick muscular walls because they need to pump blood with great force into the pulmonary artery and aorta to circulate it throughout the body.
2. (b) Mammals and birds are endothermic (warm-blooded) animals with high metabolic rates and body temperatures, so they need a high supply of oxygen to produce energy, which requires keeping oxygenated and deoxygenated blood completely separated for efficient circulation.

Answer: (a) To pump blood with force to the lungs and body. (b) To maintain high body temperature and metabolic rate by ensuring efficient oxygen supply.

1. Step 1: Cross the parents (P generation). Tall pea plant (TT) is crossed with a dwarf pea plant (tt). The gametes from the tall parent are T and from the dwarf parent are t. The F₁ generation offspring are all Tt (Tall).
2. Step 2: Self-cross the F₁ generation (Tt × Tt) to obtain the F₂ generation. The gametes produced by each F₁ parent are T and t.
3. Step 3: Construct the checkerboard (Punnett square) for the F₂ generation. Place gametes T and t on the top and left side. The resulting genotypes are: TT (top-left), Tt (top-right), Tt (bottom-left), and tt (bottom-right).
4. Step 4: Determine the phenotypes. TT and Tt are Tall, while tt is Dwarf. The genotypic ratio is 1 TT : 2 Tt : 1 tt. The phenotypic ratio is 3 Tall : 1 Dwarf.

Answer: F₂ genotypic ratio: 1:2:1 (TT:Tt:tt); Phenotypic ratio: 3:1 (Tall:Dwarf)

1. A trophic level is a specific position in a food chain where organisms obtain their energy, such as producers (first level) or primary consumers (second level).
2. Energy flows in only one direction because it is lost as heat at each trophic level due to metabolic processes like respiration.
3. This heat energy dissipates into the environment and cannot be captured or reused by other organisms, preventing the cycle from reversing.

Answer: A trophic level is a position in a food chain. Energy flows unidirectionally because it is lost as heat at each level and cannot be recycled.

1. (a) The four main factors that lead to the formation of new species are: 1. Variation in the population. 2. Natural selection acting on these variations. 3. Isolation of the population from the original group. 4. Accumulation of changes over a long period of time.
2. (b) Experiences gained in an individual's lifetime (acquired characters) do not pass to offspring because they do not involve any change in the DNA or genes. Since the genetic material remains unchanged, these traits are not inherited by the next generation.

Answer: (a) Variation, natural selection, isolation, and accumulation of changes. (b) Acquired characters do not involve changes in DNA, so they are not inherited.

1. Fossils are the preserved remains or traces (bones, impressions, footprints) of organisms that lived long ago.
2. Method 1 (relative): digging into the earth, fossils found closer to the surface are more recent than those in deeper layers.
3. Method 2 (fossil dating): the ratio of different isotopes of the same element (such as carbon-14 to carbon-12) in the fossil tells how old it is.

Answer: Fossils are preserved traces of past organisms; their age is found from the depth of the rock layer (relative) and by isotope (carbon) dating.

1. 1. The molecule formed in the cytoplasm during the first step of respiration (glycolysis) is pyruvic acid (or pyruvate).
2. 2. The two types of respiration are aerobic respiration and anaerobic respiration.
3. 3. Difference 1: Aerobic respiration requires the presence of oxygen, whereas anaerobic respiration occurs in the absence of oxygen.
4. 4. Difference 2: Aerobic respiration yields a large amount of energy (36-38 ATP molecules per glucose molecule), whereas anaerobic respiration yields a small amount of energy (2 ATP molecules per glucose molecule).

Answer: Pyruvic acid; Aerobic and Anaerobic respiration; Differences: Oxygen requirement and Energy yield.

1. Factors required: Sunlight, water (H₂O), carbon dioxide (CO₂), and chlorophyll.
2. Events: Light reaction splits water into hydrogen and oxygen; hydrogen combines with CO₂ to form glucose; oxygen is released as a by-product.
3. Balanced equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll).

Answer: Photosynthesis requires sunlight, water, CO₂, and chlorophyll; it converts CO₂ and water into glucose and oxygen via the equation 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

1. Draw a lateral (side) view of the human brain, showing the large rounded structure at the top and the smaller, wrinkled structure at the back-bottom.
2. Label the large, upper portion of the brain as 'Cerebrum'.
3. Label the smaller, lower portion located at the back of the brain as 'Cerebellum'.
4. Ensure the labels are clearly written with lines pointing to the correct regions.

Answer: A labeled diagram of the human brain showing the Cerebrum (large upper part) and Cerebellum (smaller lower back part).