Brain Grain · braingrain.in
Science — Practice Paper · Set 1
Class: 8Samacheer KalviMax Marks: 59
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 10 × 1 = 10
Choose the correct answer. (Answer all questions.)
1.The well – developed sporophytic plant body is seen in ……………..A. BryophytesB. PteridophytesC. GymnospermsD. Angiosperms[1]
2.Magnesium oxides are used for treating …………….A. acidityB. head painC. teeth decayD. None of these[1]
3.The menu used to save the document is –A. File → openB. file → printC. file → saveD. Edit → close[1]
4.The imaginary line passing through the centre of curvature and pole of a spherical mirror is called –A. Centre of curvatureB. PoleC. principal axisD. Radius curvature[1]
5.Solvay process is a method to manufacture –A. lime waterB. aerated waterC. distilled waterD. sodium carbonate[1]
6.The liquid metal used in thermometers is –A. CopperB. MercuryC. SilverD. Gold[1]
7.Dissolved gases like sulphur dioxide, nitrogen oxides in rain water causesA. Acid rainB. Base rainC. Heavy rainD. Neutral rain[1]
8.Brine is a concentrated solution of ………………A. Sodium sulphateB. Sodium chlorideC. Calcium chlorideD. Sodium bromide[1]
9.Heat is a form of ………….A. electrical energyB. gravitational energyC. thermal energyD. None of these[1]
10.………………… is the coal of superior quality.A. PeatB. LigniteC. BituminousD. Anthracite[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
11.Downward force : weight :: Upward force offered by liquid : ______[1]
12.Producer gas is a mixture of _______ and _______[1]
13.Sound is produced by ………… The vibrations of a simple pendulum are also known as ………… Sound travels in the form of ………… High frequency sounds that cannot be heard by you are called ………… Pitch of a sound depends on the ………… vibration. If the thickness of a vibrating string is increased, its pitch …………[1]
14.Melting point of most metal is __________ than non-metal.[1]
15.The word 'Taxonomy' is derived from ______.[1]
Part III — True or False 5 × 1 = 5
Write True or False. (Answer all questions.)
16.Acids are corrosive in nature.[1]
17.The dominant phase of the pteridophytes is diploid(2n).[1]
18.Most of the acids are not soluble in water.[1]
19.All bases are alkalis.[1]
20.Intensity of light from a candle is approximately equal to one ‘candela’.[1]
Part IV — Short Answer Questions 12 × 2 = 24
Answer briefly. (Answer all questions.)
21.What is a chemical equation?[2]
22.What is luminous Intensity?[2]
23.How does the friction arise between the surfaces of two bodies in relative motion?[2]
24.In an electroscope the connecting rod and the leaves are all metals.[2]
25.Write the symbols for these elements Oxygen Gold Calcium Cadmium Iron[2]
26.What are celestial objects?[2]
27.The propellant of a rocket is only in the form of solids.[2]
28.What type of oscillations are used in atomic clocks?[2]
29.Mention the various conditions required for a chemical reaction to occur.[2]
30.The Pictorial symbol for water given by the alchemists was –[2]
31.What do you mean by catenation?[2]
32.What are Cryogenic Fuels?[2]
Part V — Long Answer Questions 3 × 5 = 15
Answer in detail. (Answer all questions.)
33.Discuss the advantages of Insitu and exsitu conservation.[5]
34.Explain the working of thermos flask.[5]
35.What do you understand by the term bio-magnification?[5]
🔑 Show Answer Key — Set 1
- 1. (c) Gymnosperms
- 2. (a) acidity
- 3. (c) file → save
- 4. (c) principal axis
- 5. (d) sodium carbonate
- 6. (b) Mercury
- 7. (a) Acid rain
- 8. (b) Sodium chloride
- 9. (c) thermal energy
- 10. (d) Anthracite
- 11. Buoyant force.
- 12. Carbon monoxide and nitrogen
- 13. vibrating bodies oscillation mechanical waves Ultrasonic frequency of the decrease
- 14. Higher
- 15. Greek.
- 16. This statement is true. Acids are corrosive in nature, meaning they can damage or destroy materials they come into contact with. Strong acids such as sulphuric acid and hydrochloric acid are highly corrosive and can burn skin, corrode metals, and damage organic materials. Even dilute acids can be corrosive to certain substances. This corrosive property of acids is due to the presence of hydrogen ions that react with various materials. The corrosive nature of acids makes them dangerous to handle and requires proper safety precautions such as wearing protective equipment and using appropriate containers for storage and transport.
- 17. True.
- 18. This statement is false. Most of the acids are soluble in water. Acids such as hydrochloric acid, sulphuric acid, nitric acid, and acetic acid are highly soluble in water. When acids dissolve in water, they ionize and release hydrogen ions, which give acids their characteristic sour taste and corrosive properties. However, some acids like silicic acid have limited solubility in water. The solubility of acids in water is an important property that allows them to be used in various chemical reactions and applications.
- 19. This statement is false. The correct statement is that all alkalis are bases, but all bases are not alkalis. A base is a substance that can neutralize an acid and produce salt and water. Bases include metal oxides, metal hydroxides, and ammonia. An alkali is a specific type of base that is soluble in water and produces hydroxide ions. Common alkalis include sodium hydroxide, potassium hydroxide, and ammonia solution. Since all alkalis are soluble bases that produce hydroxide ions in water, they are all bases. However, not all bases are alkalis because some bases like metal oxides are insoluble in water and do not produce hydroxide ions directly. Therefore, the relationship between bases and alkalis is that alkalis form a subset of bases, not the other way around.
- 20. True. The intensity of light from a candle is approximately equal to one candela. The candela is the SI unit of luminous intensity, which measures the brightness of light emitted in a particular direction. Historically, the candela was defined based on the light produced by a standard candle, and a typical candle produces a luminous intensity of approximately one candela.
- 21. A chemical equation is a shorthand representation of a chemical reaction using chemical symbols and formulas of the reactants and products. It shows which substances react together (reactants) and what new substances are formed (products). For example, the equation 2H₂ + O₂ → 2H₂O represents the reaction between hydrogen and oxygen to form water. Chemical equations must be balanced so that the number of atoms of each element is the same on both sides, obeying the Law of Conservation of Mass. They provide a concise way to communicate chemical information and are essential for understanding and predicting the outcomes of chemical reactions.
- 22. Luminous intensity is the measure of the power of the emitted light by a light source in a particular direction, per unit solid angle. It describes how bright a light source appears in a specific direction and is measured in candelas in the SI system. Luminous intensity is different from total luminous flux, as it focuses on the brightness in a particular direction rather than the total light emitted in all directions. This property is important in applications such as lighting design, where the directional brightness of a source matters significantly.
- 23. Friction arises between the surfaces of two bodies in relative motion due to the interlocking of the irregularities present on the two surfaces. Even though surfaces may appear smooth to the naked eye, they have microscopic irregularities, bumps, and valleys on them. When two surfaces are in contact and move relative to each other, these irregularities interlock and resist the motion. The force required to overcome this interlocking of surface irregularities is what we call friction. The greater the roughness of the surfaces, the greater the interlocking and hence the greater the friction.
- 24. In an electroscope, the connecting rod and the leaves are made of metals because metals are excellent conductors of electricity. Metals contain a large number of free electrons that can move easily through the material. This property allows the charge to travel freely from the metal disc through the connecting rod to the leaves without any obstruction. If non-conducting materials were used instead, the charge would not be able to move through the device, and the electroscope would not function properly. The free movement of electrons in metals is essential for the electroscope to detect and display the presence of electric charge.
- 25. S.No Element Symbols (i) Oxygen O (ii) Gold Au (iii) Calcium Ca (iv) Cadmium Cd (v) Iron Fe
- 26. The stars, the planets, the Moon and any other objects like asteroids and comets in the sky are called celestial objects.
- 27. False Correct statement: The propellant of a rocket is may be in the form of solids or liquids.
- 28. The type of oscillations used in atomic clocks are periodic vibrations of atoms, specifically the oscillations of electrons in atoms. Atomic clocks use the natural frequency of oscillation of atoms such as cesium or rubidium. These oscillations are extremely regular and consistent, making atomic clocks the most accurate timekeeping devices available, with precision far exceeding that of mechanical or quartz clocks.
- 29. Various conditions are required for a chemical reaction to occur. These include physical contact between reactants, which allows them to interact. The reactants may need to be in solution form to facilitate the reaction. External energy sources such as heat, light, or electricity can initiate or accelerate chemical reactions. Additionally, a catalyst, which is a substance that speeds up the reaction without being consumed, may be required. Some reactions occur spontaneously at room temperature, while others require specific conditions like high temperature or pressure to proceed. The concentration and nature of reactants also play important roles in determining whether a reaction will occur and how quickly it will proceed.
- 30. (refer textbook)
- 31. Catenation is the property of carbon atoms to form bonds with itself, resulting in the formation of long chains or large structures. This unique ability of carbon to bond with other carbon atoms through single, double, or triple covalent bonds allows it to create an enormous variety of organic compounds. Catenation is one of the most important properties of carbon and is the fundamental reason why carbon forms the basis of all organic chemistry. Due to catenation, carbon can form linear chains, branched chains, and ring structures, leading to the existence of millions of different organic compounds. This property distinguishes carbon from most other elements and makes it the central element in the chemistry of living organisms.
- 32. Cryogenic fuels are specialized fuels used in rocket engines that are maintained and stored at very low temperatures in order to keep them in liquid state. These fuels, such as liquid hydrogen and liquid oxygen, provide high energy density and are highly efficient for rocket propulsion. The term cryogenic refers to the extremely cold temperatures required, typically below minus 150 degrees Celsius, at which these substances remain in their liquid form rather than gaseous form.
- 33. In-situ conservation refers to the protection and management of species within their natural habitats and ecosystems. The advantages of in-situ conservation include that species can remain adapted to their natural habitat and continue to evolve naturally. Species can interact with each other and maintain their ecological relationships and food chains. The natural habitat and biodiversity are preserved in their original form. This method is generally less expensive and easier to manage compared to other conservation approaches. Additionally, the interests and rights of indigenous people who depend on these forests and wildlife are protected. Ex-situ conservation, on the other hand, involves protecting species outside their natural habitats, such as in zoos, botanical gardens, and breeding centers. The advantages of ex-situ conservation include that it can prevent the decline and extinction of endangered species by providing a safe environment for their survival. Endangered animals can be bred in captivity under controlled conditions, which increases their population numbers. Threatened species can be bred in these facilities and then released back into their natural environment to restore wild populations. Ex-situ conservation is also useful for conducting scientific research and educational work about species biology, behavior, and genetics. Both approaches are important and complementary in overall wildlife conservation strategy.
- 34. A thermos flask has double walls that are evacuated to create a vacuum between them. The inner surfaces of these walls are silvered. The vacuum between the two walls is highly effective at preventing heat transfer by conduction and convection because there are very few air molecules present to conduct heat or create convection currents. Since conduction requires matter to transfer heat through direct contact, the absence of air in the vacuum space eliminates this pathway almost entirely. Heat can only be conducted at the points where the two walls physically meet, which occurs at the top of the flask and through a small insulated support at the bottom. These contact points are minimal, so conduction losses are negligible. Additionally, the silvered surfaces on the inner walls act as reflectors that bounce radiated heat back toward the liquid inside the flask, preventing heat loss through radiation. By minimizing all three modes of heat transfer—conduction, convection, and radiation—the thermos flask effectively maintains the temperature of the liquid inside for extended periods.
- 35. Bio-magnification is the process by which the concentration of toxic or contaminated substances increases progressively at each successive level of the food chain. The contaminants involved are typically heavy metals such as mercury and arsenic, and pesticides such as polychlorinated biphenyls and DDT (Dichloro Diphenyl Trichloro ethane). These harmful substances are taken up by organisms through the food they consume. When organisms at higher trophic levels feed on organisms at lower trophic levels that contain these toxins, the toxins accumulate in the bodies of the higher organisms. Since the higher organisms consume many lower organisms over their lifetime, the concentration of these toxins becomes much greater in their bodies than in the organisms they feed upon. This means that top predators accumulate the highest concentrations of these toxic substances, even though the initial concentration in the environment may be very low. Bio-magnification is a serious environmental concern because it can cause severe health problems and even death in animals at the top of the food chain, including humans who consume contaminated organisms.
Brain Grain · braingrain.in
Science — Practice Paper · Set 2
Class: 8Samacheer KalviMax Marks: 59
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 10 × 1 = 10
Choose the correct answer. (Answer all questions.)
1.Amount of substance isA. Directly proportional to the number of atomsB. Inversely proportional to the number of atomsC. Directly proportional to the square of number of atomsD. Inversely proportional to the square of number of atoms[1]
2.……………… joints are immovable.A. Shoulder and armB. Knee and jointC. Upper jaw and skullD. Lower jaw and upper jaw[1]
3.…………….. metal undergoes rusting.A. TinB. SodiumC. CopperD. Iron[1]
4.The shape of the Earth’s magnetic field resembles that of an imaginary ………………A. U-shaped magnetB. straight conductor carrying currentC. solenoid coilD. bar magnet[1]
5.The period at which an organism attains sexual maturity is called ………………A. pubertyB. adolescenceC. growthD. maturity[1]
6.Which one of the following devices is used to measure electric current[1]
7.Soil erosion is prevented by …………….. plants.A. AlgaeB. FungiC. BryophytesD. Pteridophytes[1]
8.If the amplitude and frequency of a sound wave are increased, which of the following is true?A. Loudness increases and pitch is higherB. Loudness increases and pitch is unchangedC. Loudness increases and pitch is lowerD. Loudness decreases and pitch is lower[1]
9.Which of the following factor induces electrolysis?A. HeatB. LightC. ElectricityD. Catalysis[1]
10.1. Atom (A) building block of matter 2. Element (B) atoms of different kinds 3. Compound (C) atoms of the same kind 4. Molecule (D) smallest unit of a substanceA. 1 – A, 2 – C, 3 – B, 4 – DB. 1 – C,2 – A, 3 – B, 4 – DC. 1 – D, 2 – C, 3 – B, 4 – AD. 1 – B, 2 – C, 3 – A, 4 – D[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
11.__________ are used to lift heavy iron pieces.[1]
12.……………. is called as vital life. Nitrogen is ……………. than air. ……………. is used as a fertilizer. Dry ice is used as a ……………. The process of conversion of iron into hydrated form of oxides is called …………….[1]
13.In acidic solution, the colour of hibiscus indicator paper changes to ______.[1]
14.Water is colourless, odourless and …………. The boiling point of water is …………. Temporary hardness of water can be removed by …………. of water The density of water is maximum at ………….. Loading speeds up the process of …………..[1]
15.The chemicals used for killing the weeds or inhibiting their growth are called as __________[1]
Part III — True or False 5 × 1 = 5
Write True or False. (Answer all questions.)
16.Viscosity depends on the pressure of a liquid.[1]
17.During pregnancy, the corpus luteum continues to grow and produces large amount of estrogen and progesterone.[1]
18.Acids are bitter in taste.[1]
19.All bryophytes are hydrophytes.[1]
20.A moving body comes to rest due to friction alone.[1]
Part IV — Short Answer Questions 12 × 2 = 24
Answer briefly. (Answer all questions.)
21.Define – ampere.[2]
22.Universal solvent – Water Pollutant Hard water – Kills germs Boiling – Ozonisation Sterilization – Water Sewage – Stomach ailments[2]
23.Write the names of the following compounds. CO N 2 O NO 2 PCl 5[2]
24.What is tissue culture?[2]
25.How to close a document?[2]
26.List out the base quantities with their units.[2]
27.A sound wave travels 2000 m in 8 s. What is the velocity of the sound?[2]
28.What is magnetic field?[2]
29.What do you mean by weeding?[2]
30.Define Muscle.[2]
31.Why are bells made of metals?[2]
32.State the Law of Conservation of Mass.[2]
Part V — Long Answer Questions 3 × 5 = 15
Answer in detail. (Answer all questions.)
33.Explain how food items are spoilt due to chemical reactions?[5]
34.What is Tarnishing? Give an example.[5]
35.Expand CNG. List out its uses.[5]
🔑 Show Answer Key — Set 2
- 1. (a) directly proportional to the number of atoms
- 2. (c) Upper jaw and skull
- 3. (d) Iron
- 4. (d) bar magnet
- 5. (a) puberty
- 6. (refer textbook)
- 7. (c) Bryophytes
- 8. (a) Loudness increases and pitch is higher
- 9. (c) Electricity
- 10. A C B D
- 11. Electromagnets
- 12. Oxygen lighter Nitrogen refrigerant rusting
- 13. Deep pink or deep red.
- 14. tasteless 100°C boiling 4°C Sedimentation
- 15. herbicides
- 16. True. Viscosity depends on the pressure of a liquid. Viscosity is the measure of a liquid's resistance to flow, and it is affected by various factors including pressure. When pressure on a liquid increases, the molecules are forced closer together, which increases the internal friction between molecules and thus increases the viscosity of the liquid. Conversely, when pressure decreases, the viscosity of the liquid decreases. Temperature also affects viscosity, but pressure is a significant factor in determining how easily a liquid flows.
- 17. This statement is true. During pregnancy, the corpus luteum, which is a temporary endocrine gland formed after ovulation, continues to grow and produces large amounts of estrogen and progesterone. These hormones are essential for maintaining the pregnancy. Progesterone, in particular, helps to maintain the uterine lining and prevents further ovulation during pregnancy. The corpus luteum continues to function and produce these hormones throughout the early stages of pregnancy until the placenta develops sufficiently to take over hormone production. This hormonal support is crucial for the successful development of the embryo and fetus within the uterus.
- 18. This statement is false. The correct statement is that acids are sour in taste, not bitter. Sourness is the characteristic taste property of acids due to the presence of hydrogen ions. Common examples include vinegar, lemon juice, and citric acid, which all taste sour. Bases, on the other hand, are bitter in taste. Bases such as sodium hydroxide and ammonia solution have a bitter taste. It is important to distinguish between the taste properties of acids and bases, as this is one of the key ways to identify them in laboratory settings.
- 19. False. The correct statement is that all bryophytes are amphibians, not hydrophytes. Bryophytes, which include mosses and liverworts, are called amphibians because they can survive both in aquatic and terrestrial environments. They require moisture for reproduction but can also live on land, making them intermediate between purely aquatic and purely terrestrial plants.
- 20. True. A moving body will come to rest due to friction alone. Friction is a force that opposes the motion of an object and acts in the direction opposite to the velocity of the object. When friction is the only force acting on a moving body, it continuously removes the kinetic energy of the object, causing it to decelerate. Eventually, the object loses all its kinetic energy and comes to rest. This is observed in everyday situations, such as when a ball rolled on the ground gradually slows down and stops due to friction between the ball and the ground surface.
- 21. One ampere is defined as one coulomb of charge moving in a conductor in one second. In other words, if a charge of one coulomb passes through a cross-section of a conductor in one second, the electric current flowing through that conductor is said to be one ampere. Ampere is the SI unit of electric current and is named after the French physicist André-Marie Ampère. It is one of the seven base units in the International System of Units.
- 22. Universal solvent – Water; Water Pollutant – Sewage; Hard water – Kills germs (incorrect match, should be Sterilization); Boiling – Ozonisation (incorrect match); Sterilization – Kills germs; Water – Universal solvent. The correct matches are: Universal solvent – Water, Water Pollutant – Sewage, Sterilization – Kills germs, Boiling – Purification method, and Ozonisation – Water purification method.
- 23. Carbon monoxide. Nitrous oxide Nitrogen dioxide Phosphorous pentachloride
- 24. Tissue culture is a biotechnological technique of growing plant cells, tissues, organs, seeds, or other plant parts in a sterile environment on a nutrient medium. This method allows plants to be propagated and multiplied rapidly in laboratory conditions without the need for seeds or traditional propagation methods. Tissue culture is useful for producing disease-free plants, preserving endangered plant species, and creating uniform plants with desirable characteristics.
- 25. Close the current document by selecting File → Close command on the menu bar or click the Close icon if it is visible on the Standard tool bar.
- 26. The seven base quantities and their corresponding SI units are as follows: length is measured in metres, mass in kilograms, time in seconds, electric current in amperes, temperature in kelvin, amount of substance in moles, and luminous intensity in candelas. These base quantities are fundamental and independent of each other, and all other physical quantities can be derived from combinations of these base quantities and their units. For example, velocity is derived from length and time, force is derived from mass, length, and time, and energy is derived from mass, length, and time.
- 27. Given data: Distance travelled by a sound wave d = 2000 m time taken t = 8s To find: Velocity of sound V = ? Formula:
- 28. The space around a magnet in which its magnetic effect or influence is observed.
- 29. Weeding is the process of removing undesirable plants that grow naturally along with crop plants in the field. These undesirable plants are called weeds. Weeds compete with crop plants for water, nutrients, sunlight, and space, which reduces the growth and yield of the main crop. Weeding is an important agricultural practice that helps ensure the crop plants receive adequate resources for healthy growth and better production.
- 30. A muscle is a bundle of contractile tissue composed of muscle fibers that have the ability to contract and relax. Muscles have two main ends: the origin, which is the fixed end attached to a bone that does not move during contraction, and the insertion, which is the movable end that pulls another part of the body. When muscles contract, they shorten and pull on the bones to which they are attached through tendons, causing movement of body parts and enabling locomotion and various other functions.
- 31. Bells are made of metals because metals possess the property of sonority. When metals are struck or hit, they produce a clear, ringing sound that can be heard from a distance. This property of producing sound when struck is called sonorousness, and it is a characteristic feature of metals. The vibrations created when a bell is struck cause the metal to oscillate, producing sound waves that travel through the air. This is why metals like bronze and brass are preferred materials for making bells in temples, schools, and other places where loud, clear sounds are needed.
- 32. The Law of Conservation of Mass states that during any chemical change, the total mass of the products is equal to the total mass of the reactants. This fundamental principle means that matter cannot be created or destroyed in a chemical reaction, only rearranged. For example, when hydrogen burns in oxygen to form water, the mass of water produced equals the combined mass of hydrogen and oxygen that reacted. This law was established by Antoine Lavoisier and forms the basis for balancing chemical equations and understanding the nature of chemical reactions.
- 33. 1. Spoilage of food and vegetables: Food spoilage may be defined as any change that causes food unfit for human consumption. The chemical reactions catalyzed by the enzymes result in the degradation of food quality such as development of bad taste and odour, deterioration and loss of nutrients. Example 1 : Rotten eggs develop a bad smell due to formation of hydrogen sulphide gas. Example 2 : Decaying of vegetables and fruits due to microbes. 2. Rancidity of fishes and meat: Fishes and meat containing high levels of polyunsaturated fatty acids that undergo oxidation causes bad odour when exposed to air or light. This process is called rancidity. 3. Apples and fruits turn brown when cut: Apples and some fruits turn brown due to chemical reaction with oxygen in air. This chemical reaction is called browning. The cells of apples, fruits and other vegetables contain an enzyme called polyphenol oxidase or tyrosinase, when come in contact with oxygen catalyses a biochemical reaction of plants, phenolic compounds to brown pigments known as melanins.
- 34. Tarnishing is the process by which shiny metal surfaces and articles lose their bright, shining appearance due to chemical reactions occurring on their surface when exposed to air, moisture, or other atmospheric conditions. Silver articles become black on exposure to atmospheric air because silver reacts with sulphur compounds present in the air to form silver sulphide, which is black in colour. Similarly, brass vessels, which contain copper as one of their constituents, develop a greenish layer on prolonged exposure to air. This greenish layer is formed due to a chemical reaction between copper and moist air, resulting in the formation of basic copper carbonate and copper hydroxide. Tarnishing is a slow chemical change that affects the appearance of metal articles but does not necessarily affect their functionality. The tarnished layer can often be removed by polishing or chemical treatment to restore the original shine of the metal.
- 35. CNG stands for Compressed Natural Gas. It is one of the cheapest and cleanest fuels available for use in vehicles and industrial applications. CNG is primarily used as a fuel for automobiles, buses, and trucks, offering significant environmental and economic advantages. Vehicles powered by CNG produce considerably less carbon dioxide and hydrocarbon emissions compared to those running on petrol or diesel, making it an environmentally friendly choice. CNG is also less expensive than both petrol and diesel, which makes it economically attractive for consumers. Additionally, CNG can be used in power generation plants and as a fuel for cooking in households. Its lower pollution levels and reduced greenhouse gas emissions make it a preferred alternative fuel in urban areas where air quality is a concern. The widespread adoption of CNG-powered vehicles has helped reduce urban air pollution significantly in many cities.
Brain Grain · braingrain.in
Science — Practice Paper · Set 3
Class: 8Samacheer KalviMax Marks: 59
Name: ____________________Reg No: ____________
Part I — Multiple Choice Questions 10 × 1 = 10
Choose the correct answer. (Answer all questions.)
1.Sodium hydroxide is a …………….A. acidB. baseC. oxideD. alkali[1]
2.MRI stands for………………A. Magnetic Running ImageB. detection of magnetic fieldC. navigationD. Magnetic Radar Imaging[1]
3.An electroscope has been charged by induction with the help of charged glassrod. The charge on the electroscope is –A. negativeB. positiveC. both positive and negativeD. None of the above[1]
4.Which of the following is not present in Panchakavya?A. cow dungB. cow’s urineC. curdD. sugar[1]
5.Which of the following is the working principle of Rockets?A. Newton’s first lawB. Newton’s second lawC. Newton’s third lawD. All the above[1]
6.Chandrayaan -1 was launched on …………….A. 22nd October 2008B. 8th November 2008C. 22nd July 2019D. 22nd October 2019[1]
7.Which of the following a simple circuit must have?A. Energy Source, Battery, LoadB. Energy Source, Wire, LoadC. Energy Source, Wire, SwitchD. Battery, Wire, Switch[1]
8.The first vascular cryptogams in land plants are …………….A. BryophytesB. PteridophytesC. GymnospermD. Angiosperm[1]
9.The range of audible frequency for the human ear is …………..A. 2 Hz to 2000 HzB. 20 Hz to 2000 HzC. 20 Hz to 20000 HzD. 200 Hz to 20000 Hz[1]
10.The centre of a sphere of which the reflecting surface of a spherical mirror is a part is called –A. PoleB. Centre of curvatureC. Cradius of curvatureD. Aperture[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
11.The body which has lost electrons becomes ________[1]
12.Xylem and phloem are absent in ______ plants.[1]
13.The mirror used by the ophthalmologist to examine the eye is ___________.[1]
14.Movement of organisms from place to place is called ……………….. ……………….. refers to change in position of the part of an organisms body. A structure which provides rigid frame work to the body is called ……………….. Axial skeleton in human consists of ……………….., ……………….., ………………..and ………………… Appendicular skeleton in human consists of ……………….. and ………………… The place where two bones meet is termed as ………………… ……………….. is attached to soft parts of the body like blood vessels, iris, bronchi and the skin ……………….. muscle makes pupil of eyes wider.[1]
15.An example for fossil fuel is __________[1]
Part III — True or False 5 × 1 = 5
Write True or False. (Answer all questions.)
16.The number 4.582 can be rounded off as 4.58.[1]
17.Liquid pressure decreases with the decrease of depth.[1]
18.Water can conduct electricity.[1]
19.In parallel circuit, current remains the same in all components.[1]
20.Cell wall of fungi is made up of chitin.[1]
Part IV — Short Answer Questions 12 × 2 = 24
Answer briefly. (Answer all questions.)
21.Define one calorie.[2]
22.What is the SI unit of Luminous Intensity?[2]
23.Seeds of gymnosperm plants are naked. Why?[2]
24.What is an electric circuit?[2]
25.What is an ultrasonic sound?[2]
26.Why does a light paddle wheel placed in the path of cathode rays begin to rotate, when cathode rays fall on it?[2]
27.Name the bacteria used in the production of vinegar.[2]
28.Latent heat of fusion.[2]
29.How can you identify non-magnetic materials? Give an example of a non- magnetic material.[2]
30.What is selecting text?[2]
31.What is crop rotation?[2]
32.How to open an existing document?[2]
Part V — Long Answer Questions 3 × 5 = 15
Answer in detail. (Answer all questions.)
33.What is green manure?[5]
34.What is permanent hardness of water? How can it be removed?[5]
35.Give an example to show that light travels faster than sound.[5]
🔑 Show Answer Key — Set 3
- 1. (d) alkali
- 2. (a) Magnetic Resonance Imaging
- 3. (b) positive
- 4. (d) sugar
- 5. (c) Newton’s third law
- 6. (a) 22nd October 2008
- 7. (d) Battery, Wire, Switch
- 8. (b) Pteridophytes
- 9. (c) 20 Hz to 20000 Hz
- 10. (b) Centre of curvature
- 11. positive
- 12. Bryophyte plants.
- 13. Concave mirror
- 14. locomotion Movement skeleton Skull facial bones. sternum. ribs, vertebral column Pelvic, Pectoral girdle Joint Smooth muscle Radial
- 15. Coal
- 16. True. The number 4.582 can be rounded off as 4.58. When rounding to two decimal places, we look at the third decimal digit, which is 2. Since 2 is less than 5, we round down, keeping the second decimal place as 8. Therefore, 4.582 rounded to two decimal places is 4.58.
- 17. True. Liquid pressure decreases with the decrease of depth. Pressure in a liquid is directly proportional to the depth below the surface. As you move deeper into a liquid, the weight of the liquid column above increases, resulting in greater pressure. Conversely, as depth decreases and you move toward the surface, the weight of the liquid column above becomes smaller, causing the pressure to decrease. At the surface of a liquid, the pressure is minimum.
- 18. True. Pure water is a poor conductor of electricity because it has very few free ions. However, ordinary water found in nature or used in daily life contains dissolved salts and minerals that dissociate into ions. These ions are charge carriers that allow electric current to flow through water. Therefore, water can conduct electricity, especially when it contains dissolved salts or other ionic compounds.
- 19. False. In a parallel circuit, the voltage remains the same across all components, not the current. Each component in a parallel circuit is connected directly across the same two points, so they all experience the same potential difference. However, the current through each component can be different depending on the resistance of that component. The total current from the power source is divided among the different branches of the parallel circuit according to Ohm's law, so the current in each branch may vary.
- 20. True. The cell wall of fungi is made up of chitin, which is a complex polysaccharide. This is one of the key characteristics that distinguishes fungi from plants, whose cell walls are composed of cellulose. The presence of chitin in fungal cell walls makes them structurally similar to the exoskeletons of insects and arthropods.
- 21. One calorie is the amount of heat energy required to raise the temperature of one gram of water through one degree Celsius. The calorie is a unit of heat energy commonly used in physics and chemistry. It is important to note that the calorie used in everyday contexts, such as in nutrition and food energy content, is actually the kilocalorie (kcal), which equals one thousand calories. One calorie is equivalent to approximately 4.18 joules in the International System of Units (SI). This definition of the calorie is based on the specific heat capacity of water, which is one calorie per gram per degree Celsius.
- 22. The SI unit of luminous intensity is candela, abbreviated as cd. Candela is one of the seven fundamental SI units and is used to measure the intensity of light emitted by a source in a particular direction. It is defined based on the light produced by a standard source and is essential for measuring the brightness of light sources in various applications.
- 23. Seeds of gymnosperm plants are naked because in gymnosperms, the ovules are borne directly on the surface of megasporophylls or cone scales, and no flowers are produced. Since the ovules are not enclosed within an ovary or fruit, the seeds remain exposed or naked after fertilization. This is why gymnosperms are also called open seed-bearing plants, in contrast to angiosperms where seeds are enclosed within a fruit.
- 24. The path through which electrons flow from one terminal to the other terminal of a source is called an electric circuit.
- 25. A sound with a frequency greater than 20000 Hz is called as ultrasonic sound.
- 26. A light paddle wheel placed in the path of cathode rays begins to rotate when cathode rays fall on it because the cathode rays consist of small particles called electrons that possess both mass and energy. When these electrons strike the paddle wheel, they transfer their kinetic energy to it, causing it to rotate. This demonstrates that cathode rays are not merely waves but are composed of material particles with momentum. The impact of these energetic particles on the paddle wheel provides mechanical energy that overcomes friction and sets the wheel in motion, providing experimental evidence for the particle nature of cathode rays.
- 27. Acetobacter aceti.
- 28. The amount of heat energy required by ice to change into water at its melting point (0°C) without any change in temperature is called latent heat of fusion of ice. This heat energy is absorbed by the ice molecules to overcome the forces of attraction between them, allowing them to transition from a solid crystalline structure to a liquid state. The latent heat of fusion is a specific property of ice and remains constant at a given pressure.
- 29. Non-magnetic materials are materials that are not attracted by magnets and do not respond to magnetic force. To identify non-magnetic materials, you can bring a magnet close to the material and observe whether it is attracted to the magnet or not. If the material is not attracted to the magnet, it is a non-magnetic material. Examples of non-magnetic materials include wood, glass, rubber, plastic, and aluminium. These materials do not contain ferromagnetic properties and therefore do not experience any force of attraction when placed near a magnet.
- 30. Selecting is the process of highlighting text or picking an object. For example, a user may select text to copy, cut or move that text to an alternate location or select a file they want to view.
- 31. Crop rotation is the agricultural practice of planting a series of different crops in the same field following a defined sequence or order over successive seasons or years. This practice helps to maintain and improve the fertility of the soil by allowing different crops to utilize different nutrients and by allowing the soil to recover. Crop rotation also helps reduce pest and disease buildup in the soil, as different pests and diseases are specific to certain crops. By rotating crops, farmers can reduce the need for chemical pesticides and fertilizers, making farming more sustainable and economical.
- 32. To open an existing document, do any one of the following methods: Click the Open File button on the menu bar. Choose File → Open command from the menu bar. Press CTRL+O keys on the keyboard. Each of the above method will show the Open dialog box. Choose the file and click the Open button.
- 33. Green manure is a technique in which certain plants such as sun hemp or guar are grown in the field prior to the sowing of the main crop seeds. These plants are then ploughed back into the soil where they gradually decompose and turn into organic matter that enriches the soil. This decomposed plant material acts as green manure and helps in enriching the soil with essential nutrients, particularly nitrogen and phosphorus, which are vital for plant growth. The application of green manure always enhances the growth, development, and yield of the subsequent crops grown in that field. This practice is an environmentally friendly way to maintain soil fertility without relying heavily on chemical fertilizers.
- 34. Permanent hardness of water is the hardness caused by the presence of soluble chloride and sulphate salts of calcium and magnesium dissolved in water. Unlike temporary hardness, permanent hardness cannot be removed by simple boiling and requires specific chemical or physical treatment methods. Permanent hardness can be removed by several methods. The first method is adding washing soda, which is sodium carbonate. When washing soda is added to hard water, it reacts with the calcium and magnesium chlorides and sulphates to form insoluble calcium carbonate and magnesium carbonate. These insoluble carbonates settle down and are removed by filtration, leaving behind soft water that is suitable for washing and other purposes. The second method is distillation, which is a physical process that can remove both temporary and permanent hardness from water. In distillation, water is heated to boiling point to produce steam, which is then condensed back into liquid form in a separate container. Since the dissolved salts and minerals do not vaporize along with water, they are left behind in the original container. The water obtained after distillation is called distilled water and is the purest form of water, containing no dissolved salts or minerals. Distilled water is suitable for use in laboratories, batteries, and other applications where pure water is required.
- 35. Lightning: The most common example of showing that light travels faster than sound is lightning. Whenever a lightning strikes, you see the lightning first and then hear the thunder after some time.