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.Which of the following is a water pollutant?A. LeadB. AlumC. OxygenD. Chlorine[1]
2.When an ebonite rod is rubbed with fur, the charge acquired by the fur is –A. negativeB. positiveC. partly positive and partly negativeD. None of these[1]
3.Which of the following is not present in Panchakavya?A. cow dungB. cow’s urineC. curdD. sugar[1]
4.Red ant sting contains ……………. (b sulphuric acidA. acetic acidC. oxalic acidD. formic acid[1]
5.One of the following is an example for a permanent magnet.A. ElectromagnetB. MumetalC. Soft ironD. Neodymium[1]
6.Organism that control insects and pests of plant crops is …………………A. bio-pesticidesB. bio-fertilizersC. earthwormsD. neem leaves[1]
7.Which of the following statements about approximation is wrong?A. Approximation gives accurate value.B. Approximation simplifies the calculation.C. Approximation is very useful when little information is available.D. Approximation gives the nearest value only.[1]
8.……………. is a prokaryotic micro organisms.A. VirusB. AlgaeC. FungiD. Bacteria[1]
9.The liquid metal used in thermometers is –A. CopperB. MercuryC. SilverD. Gold[1]
10.Which is known as syn gas?A. Marsh gasB. Water gasC. Producer gasD. Coal gas[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
11.The spherical mirror used in a beauty parlour as make-up mirror is ___________.[1]
12.Microorganism can be seen with the help of a _______.[1]
13.The size of the cells are measured in units of ______________[1]
14.Monocotyledon seed bears only ______ cotyledon.[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 Sun and the celestial bodies form Solar system.[1]
17.Binomial name should contains more than two words.[1]
18.Water can conduct electricity.[1]
19.Skull in humans consists of 22 bones.[1]
20.Gallium metal is in solid state at or just above room temperature.[1]
Part IV — Short Answer Questions 12 × 2 = 24
Answer briefly. (Answer all questions.)
21.Name the processes by which air enters and comes out of our lungs?[2]
22.How can you identify non-magnetic materials? Give an example of a non- magnetic material.[2]
23.What is electric current?[2]
24.Who discovered penicillin?[2]
25.What do you mean by catenation?[2]
26.Specific heat capacity.[2]
27.Latent heat of fusion.[2]
28.Define one atmosphere.[2]
29.Write the names of the following compounds. CO N 2 O NO 2 PCl 5[2]
30.Is it possible to find Dinosaurs today? Why?[2]
31.What is an ultrasonic sound?[2]
32.Name the bacteria used in the production of vinegar.[2]
Part V — Long Answer Questions 3 × 5 = 15
Answer in detail. (Answer all questions.)
33.Take some water in a vessel and heat it on a stove. Touch the surface of the water. It will be cold. Touch it after some time. It will be hot now. How did the heat which was supplied at the bottom reach the top?[5]
34.Rub your foot on a carpet floor and touch a door knob. What do you feel? Do you feel the shock in your hand? Why does this happen?[5]
35.Give an example to show that light travels faster than sound.[5]
🔑 Show Answer Key — Set 1
- 1. (a) Lead
- 2. (b) positive
- 3. (d) sugar
- 4. (d) formic acid
- 5. (d) Neodymium
- 6. (a) bio-pesticides
- 7. (a) Approximation gives accurate value.
- 8. (d) Bacteria
- 9. (b) Mercury
- 10. (b) Water gas
- 11. Concave mirror
- 12. Microscope
- 13. Microns
- 14. One.
- 15. Coal
- 16. true
- 17. False. The correct statement is that a binomial name should contain exactly two words. The binomial nomenclature system, developed by Carl Linnaeus, uses a two-part naming system where the first word represents the genus and the second word represents the species. This two-word format is the fundamental principle of binomial nomenclature.
- 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. True. The skull in humans consists of 22 bones. These bones are fused together to form a protective structure that encloses and protects the brain. The skull bones include the cranium, which forms the main vault of the skull, and the facial bones, which form the structure of the face. This statement is accurate according to standard human anatomy.
- 20. False. The correct statement is: Gallium (Ga) becomes liquid at or just above room temperature. Gallium is a unique metal with a melting point of approximately 29.76 degrees Celsius, which is just slightly above normal room temperature. This means that gallium will melt in your hand or in warm water, making it one of the few metals that is solid at room temperature but can easily transition to a liquid state with a slight increase in temperature.
- 21. The process of taking air into the lungs is called inspiration or inhalation. During this process, the diaphragm contracts and moves downward, the rib cage expands, and the volume of the thoracic cavity increases, allowing air to flow into the lungs through the nose and mouth. The process of expelling air from the lungs is called expiration or exhalation. During this process, the diaphragm relaxes and moves upward, the rib cage contracts, and the volume of the thoracic cavity decreases, pushing air out of the lungs through the nose and mouth. These two processes together form the breathing cycle that enables gas exchange in the lungs.
- 22. 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.
- 23. Electric current is the flow of electric charge through a conductor. The magnitude of an electric current is the amount of electric charges flowing through a conductor in one second. It is measured in amperes, where one ampere represents the flow of one coulomb of charge per second. Electric current can flow through various materials such as metals, liquids, and gases, and it is the basis for all electrical phenomena and applications.
- 24. Alexander Flemming.
- 25. 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 eleme…
- 26. Specific heat capacity is the amount of heat energy that is required to raise the temperature of a unit mass of a substance by 1°C (or 1 Kelvin). It is expressed in units of joules per kilogram per degree Celsius (J/kg°C). Different substances have different specific heat capacities. For example, water has a high specific heat capacity of approximately 4200 J/kg°C, which means it requires a large amount of heat to change its temperature. This property makes water useful for regulating temperature in various applications.
- 27. 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.
- 28. One atmosphere is defined as the pressure exerted by a column of mercury of height 760 millimeters at sea level under standard conditions. This standard atmospheric pressure is denoted as 1 atm. The pressure exerted by this mercury column of 760 mm height is considered as the reference pressure of magnitude one atmosphere. This definition is based on the barometric measurement of atmospheric pressure, where a mercury barometer shows a height of approximately 760 mm when measuring standard atmospheric pressure at sea level.
- 29. Carbon monoxide. Nitrous oxide Nitrogen dioxide Phosphorous pentachloride
- 30. No. It is not possible to find Dinosaurs today since they have become extinct. The reasons may be shortage of food, space or climate changes.
- 31. A sound with a frequency greater than 20000 Hz is called as ultrasonic sound.
- 32. Acetobacter aceti.
- 33. When water in a vessel is heated from below, the water molecules at the bottom receive heat energy and their kinetic energy increases. These heated molecules move faster and spread out, becoming less dense than the cooler water above them. Because they are less dense, the heated water at the bottom rises upward toward the surface. As the hot water rises, the cooler and denser water from the top sinks downward to replace it. This cooler water then comes into contact with the heat source at the bottom and gets heated in turn. The cooler water then rises, and the cycle repeats continuously. This circular motion of the fluid, where hot material rises and cool material sinks, creates convectio…
- 34. When you rub your foot on a carpet floor and then touch a doorknob, you experience an electric shock. This phenomenon occurs due to the process of charge discharge. Rubbing your foot on the carpet causes electrons to be transferred from the carpet to your body through friction. Your body accumulates a large number of excess electrons and becomes negatively charged. When you touch the doorknob, which is typically made of metal and is connected to the ground, a sudden discharge occurs. The excess electrons on your body are rapidly transferred to the doorknob and then to the ground through the metal. This rapid movement of a large number of electrons in a short time constitutes an electric c…
- 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.
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.The plants found in a particular area are known as …………….A. faunaB. floraC. endemicD. rare[1]
2.Based on shape, the bacteria are classified into …………….. types.A. 2B. 3C. 4D. 5[1]
3.…………….. is an example for colonial form of algae.A. OscillatoriaB. NostocC. VolvoxD. Chlorella[1]
4.Adolescence is the period of life between ……………… years of age.A. 10 to 16B. 11 to 17C. 11 to 19D. 11 to 20[1]
5.The method in which water flows over the soil surface and allow it to infiltrate is ………………..A. irrigationB. surface irrigationC. springier irrigationD. drip irrigation[1]
6.Which of the following statements made by Dalton has not undergone any change?A. Atoms cannot be broken.B. Atoms combine in small, whole numbers to form compounds.C. Elements are made up of atoms.D. All atoms of an elements are alike[1]
7.Chandrayaan -1 was launched on …………….A. 22nd October 2008B. 8th November 2008C. 22nd July 2019D. 22nd October 2019[1]
8.Limestone contains ………………. mainly.A. Calcium chlorideB. Calcium carbonateC. Calcium nitrateD. Calcium sulphate[1]
9.A compass is used for ………………A. plotting magnetic linesB. detection of magnetic fieldC. navigationD. All of these[1]
10.The electrification of two different bodies on rubbing is because of the transfer of –A. neutronsB. protonsC. electronsD. protons and neutrons[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
11.Knot in a thread : ______ friction :: ball bearing : friction ______[1]
12.…………….. is the smallest particle of an element. An element is composed of …………….. atoms. An atom is made up of …………….., …………….. and …………….. A negatively charged ion is called …………….. while positively charged ion is called …………….. is a negatively charged particle (Electron/Proton). Proton is deflected towards the …………….. charged plate (positively, negatively).[1]
13.If an object is placed between two mirrors which are parallel to each other, the number of images formed is __________.[1]
14.Our sun belongs to __________ Galaxy.[1]
15.Heating coal in the absence of air is called __________[1]
Part III — True or False 5 × 1 = 5
Write True or False. (Answer all questions.)
16.In a thermos flask, the silvered walls reflect and radiate the heat to the outside.[1]
17.Metals are generally good conductors of electricity, but not good conductors of heat.[1]
18.The larynx has fold of tissue which vibrate with the passage of air to produce.[1]
19.Hinge joint is slightly movable joint.[1]
20.Cardiac muscle is a voluntary muscle.[1]
Part IV — Short Answer Questions 12 × 2 = 24
Answer briefly. (Answer all questions.)
21.Why does a light paddle wheel placed in the path of cathode rays begin to rotate, when cathode rays fall on it?[2]
22.Find the valency of the element which is underlined in the following formula. Na Cl C O 2 Al (PO 2 ) Ba (NO 3 ) 2 Ca Cl 2[2]
23.Mention few measures to be taken to reduce the effect of noise pollution.[2]
24.Define catalysis.[2]
25.What is magnetic field?[2]
26.What do you mean by weeding?[2]
27.What are celestial objects?[2]
28.Define a Alchemy.[2]
29.Water unfit for drinking is called potable water.[2]
30.Define – mole.[2]
31.Define the term ions or radicals.[2]
32.What is the ‘Lower Fixed Point’ of the Fahrenheit scale?[2]
Part V — Long Answer Questions 3 × 5 = 15
Answer in detail. (Answer all questions.)
33.Why did the numbers of Tiger and Black buck decrease?[5]
34.What are the effects of acid rain? How can we prevent them?[5]
35.What are the hazards of noise pollution?[5]
🔑 Show Answer Key — Set 2
- 1. (c) endemic
- 2. (c) 4
- 3. (c) Volvox
- 4. (c) 11 to 19
- 5. (b) surface irrigation
- 6. (d) All atoms of an elements are alike
- 7. (a) 22nd October 2008
- 8. (b) Calcium carbonate
- 9. (d) All of these
- 10. (c) electrons
- 11. Rolling, Static.
- 12. Atom same kind of proton, electron, neutron anion, cation Electron negatively
- 13. Infinite
- 14. Milky way
- 15. Destructive distillation
- 16. This statement is false. The correct statement is: In a thermos flask, the silvered walls reflect radiated heat back to the liquid in the bottle. The silvered or mirrored surfaces inside a thermos flask act as reflectors for infrared radiation. When the liquid inside is hot, it radiates heat energy in the form of infrared radiation. The silvered walls reflect this radiation back into the liquid, preventing heat loss through radiation. This reflective property of the silvered walls is one of the key features that makes a thermos flask an effective insulator for keeping liquids hot or cold for extended periods.
- 17. False. The correct statement is: Metals are generally good conductors of both heat and electricity. Metals possess free electrons that move easily through their structure, allowing them to conduct electric current efficiently. Similarly, these free electrons also facilitate the transfer of heat energy through the metal, making metals excellent heat conductors. This is why metals like copper and aluminium are widely used in electrical wiring and cooking utensils respectively.
- 18. True. The larynx contains folds of tissue called vocal cords or vocal folds that vibrate when air passes through them during exhalation, producing sound. The pitch and volume of the sound can be controlled by adjusting the tension and position of these vocal cords, allowing for speech and vocalization in humans.
- 19. False. A hinge joint is a freely movable joint, not a slightly movable joint. Hinge joints allow movement in one plane only, similar to the hinge of a door. Examples of hinge joints in the human body include the elbow joint and the knee joint. Slightly movable joints, such as those between vertebrae, allow limited movement and are called gliding joints.
- 20. False. The correct statement is that cardiac muscle is an involuntary muscle. Cardiac muscles are found only in the heart and contract rhythmically without conscious control. Unlike skeletal muscles, which are voluntary and controlled by the nervous system through conscious effort, cardiac muscles work automatically to pump blood throughout the body continuously.
- 21. 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.
- 22. Na Cl = 1 C O 2 = 4 Al (PO 4 ) = 3 Ba (NO 3 ) 2 = 2 Ca Cl 2 = 2
- 23. Several important measures should be taken to reduce the effect of noise pollution. Strict guidelines and regulations should be set and enforced for the use of loudspeakers during social, religious, and political occasions to limit their duration and volume. All automobiles should be equipped with effective silencers to reduce the noise produced by engines and exhaust systems. Additionally, planting trees and creating green spaces helps absorb sound and reduces noise levels in urban areas. Noise barriers and sound-absorbing walls can be constructed along highways and near residential areas. Industries and factories should use noise-reducing equipment and maintain proper maintenance of mac…
- 24. Catalysis is the process by which the speed of a chemical reaction is altered by a substance called a catalyst. A catalyst is a chemical substance that increases or decreases the rate of a reaction without itself being permanently changed or consumed in the reaction. Catalysts work by providing an alternative pathway for the reaction with lower activation energy, allowing reactants to convert to products more quickly. The catalyst remains chemically unchanged at the end of the reaction and can be used repeatedly. Catalysts are essential in many industrial processes and biological systems. For example, enzymes act as biological catalysts in living organisms, while metallic catalysts are us…
- 25. The space around a magnet in which its magnetic effect or influence is observed.
- 26. 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.
- 27. The stars, the planets, the Moon and any other objects like asteroids and comets in the sky are called celestial objects.
- 28. Alchemy was a form of chemistry studied during the Middle Ages that was concerned with attempting to discover ways to change ordinary metals into gold. Alchemists conducted various experiments and chemical processes in their pursuit of this goal, though they were ultimately unsuccessful in transmuting base metals into precious metals. Despite its failure to achieve its primary objective, alchemy contributed to the development of early chemical knowledge and laboratory techniques that eventually laid the foundation for modern chemistry as a scientific discipline.
- 29. False Correct statement: Water suitable for drinking is called potable water.
- 30. Mole is defined as the amount of substance which contains 6.023 × 10²³ entities, such as atoms, molecules, ions, or electrons. This number is known as Avogadro's number, named after the Italian scientist Amedeo Avogadro. The mole is the SI base unit for the amount of substance and is used in chemistry to relate the microscopic world of atoms and molecules to the macroscopic quantities that we can measure in the laboratory. For example, one mole of carbon-12 has a mass of exactly 12 grams.
- 31. An ion or radical is formed when an atom or a group of atoms either loses or gains electrons. When an atom loses electrons, it becomes positively charged and is called a cation. When an atom gains electrons, it becomes negatively charged and is called an anion. A radical is a group of atoms that behaves as a single unit and carries a charge. For example, the hydroxide radical (OH⁻) consists of one oxygen atom and one hydrogen atom bonded together, carrying a negative charge. Ions and radicals are important in chemical reactions and the formation of ionic compounds.
- 32. The lower fixed point of the Fahrenheit scale is 32°F. This is the temperature at which water freezes under standard atmospheric pressure. The Fahrenheit scale was established with two fixed points: the lower fixed point at 32°F (freezing point of water) and the upper fixed point at 212°F (boiling point of water), with 180 equal divisions between them.
- 33. The numbers of tigers and black bucks have decreased significantly due to multiple interconnected factors. Excessive hunting by humans has been a major cause of their population decline, as these animals were hunted for their skin, meat, and other body parts. Deforestation has destroyed large areas of forest habitat where these animals lived, leaving them with reduced space for survival and movement. Habitat degradation, caused by human activities such as logging, agriculture, and urban expansion, has further reduced the quality of the remaining forests and grasslands. For tigers specifically, there is an additional critical problem of prey depletion. As forests disappear, the populations…
- 34. Acid rain is precipitation that contains high levels of sulfuric and nitric acids, formed when sulfur dioxide and nitrogen oxides from burning fossil fuels and industrial processes react with water vapor in the atmosphere. Acid rain has numerous harmful effects on the environment and human health. It irritates the eyes and skin of human beings, causing discomfort and potential health issues. It inhibits germination and growth of seedlings, reducing agricultural productivity and affecting forest regeneration. It changes the fertility of the soil by altering its pH and nutrient composition, which destroys plants and reduces their ability to grow. Acid rain also causes significant damage to…
- 35. Noise pollution poses numerous hazards to human health and well-being. Exposure to noise may cause irritation, stress, nervousness, and headaches in individuals. Long-term exposure to excessive noise can disrupt and change the normal sleeping patterns of a person, leading to sleep deprivation and associated health problems. Sustained and continuous exposure to high levels of noise can gradually affect and damage the hearing ability of a person, and in severe cases, it may lead to permanent loss of hearing or deafness. Sudden exposure to very loud noise can cause severe physiological reactions such as a heart attack and unconsciousness in some individuals. Noise from horns, loudspeakers, c…
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.Insitu conservation is …………….A. off site conservationB. on site conservationC. Both a and bD. None of these[1]
2.SI unit stands forA. International system of unitsB. Integrated System of unitsC. International symbol of unitsD. Integrated symbol of units[1]
3.The Red Data Book gives a list of …………….A. endemic speciesB. extinct speciesC. natural speciesD. None of these[1]
4.Magnesium oxides are used for treating …………….A. acidityB. head painC. teeth decayD. None of these[1]
5.Identify the states of matter from these molecular arrangements: A has particles far apart, B has particles tightly packed in a regular arrangement, and C has particles close together but irregularly arranged.A. A – gas, B – solid, C – liquidB. A – liquid, B – solid, C – gasC. A – solid, B – liquid, C – gasD. A – liquid, B – gas, C – solid[1]
6.1. Conduction 2.Convection 3. Radiation 4. Sublimation 5. Condensation (e) SolidA. LiquidB. Gas to liquidC. Solid to gasD. Gas[1]
7.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]
8.The refractive index of water is –A. 1.0B. 1.33C. 1.44D. 1.52[1]
9.If the image and object distance is same, then the object is placed at –A. InfinityB. At FC. Between f and PD. At C[1]
10.External ear (pinna) is supported by –A. boneB. cartilageC. tendonD. capsule[1]
Part II — Fill in the Blanks 5 × 1 = 5
Fill in the blanks. (Answer all questions.)
11.Melting point of most metal is __________ than non-metal.[1]
12.The word 'Taxonomy' is derived from ______.[1]
13.The word sour refers to ______ in Latin.[1]
14._______ is prepared from a mould called penicillium.[1]
15.The symbol of tungsten is __________[1]
Part III — True or False 5 × 1 = 5
Write True or False. (Answer all questions.)
16.A moving body comes to rest due to friction alone.[1]
17.Light energy may come out due to chemical reactions.[1]
18.Friction is the only reason for the loss of energy.[1]
19.PSLV and GSLV are India’s popular satellites.[1]
20.Acids are bitter in taste.[1]
Part IV — Short Answer Questions 12 × 2 = 24
Answer briefly. (Answer all questions.)
21.Name two instruments, which help to measure the pressure of a fluid.[2]
22.Universal solvent – Water Pollutant Hard water – Kills germs Boiling – Ozonisation Sterilization – Water Sewage – Stomach ailments[2]
23.Draw the V.S of human eye and label its parts.[2]
24.Name the Indians worked at NASA.[2]
25.It is said that sleeping beneath the tree during night is bad for health. What is the reason?[2]
26.Write the name of any nitrogen fixing bacteria.[2]
27.Why are heavy bags provided with broad straps?[2]
28.Give two examples for metalloids.[2]
29.Name the methods of sowing.[2]
30.What is tissue culture?[2]
31.What is luminous Intensity?[2]
32.Tissues, organ system, organism, cell, organ[2]
Part V — Long Answer Questions 3 × 5 = 15
Answer in detail. (Answer all questions.)
33.What is artificial magnet? Give examples.[5]
34.Explain the importance of cleanliness during the time of menstrual cycle in girls.[5]
35.Mention the uses for the following compounds. Baking soda Bleaching powder Quick lime[5]
🔑 Show Answer Key — Set 3
- 1. (b) on site conservation
- 2. (a) International system of units
- 3. (d) None of these
- 4. (a) acidity
- 5. (a) A – gas, B – solid, C – liquid
- 6. e a d c b
- 7. (b) Centre of curvature
- 8. (b) 1.33
- 9. (d) At C
- 10. (b) cartilage
- 11. Higher
- 12. Greek.
- 13. Acidus.
- 14. Penicillin
- 15. W
- 16. 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.
- 17. True. Some chemical reactions release energy in the form of light.
- 18. True. Friction is the only reason for the loss of energy in most mechanical systems. When two surfaces move relative to each other, friction converts kinetic energy into heat energy, causing energy to be dissipated from the system. This energy loss due to friction occurs in all types of motion, whether rolling, sliding, or any other form of relative motion between surfaces. The heat generated by friction represents the mechanical energy that has been lost from the system.
- 19. True.
- 20. 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.
- 21. Two instruments that help to measure the pressure of a fluid are the manometer and the pressure gauge. A manometer is a simple device that uses a liquid column to measure pressure differences and is commonly used in laboratories. A pressure gauge is an instrument that directly measures the pressure of a fluid and is widely used in practical applications such as measuring tire pressure, gas cylinder pressure, and atmospheric pressure in various industrial and domestic settings.
- 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. (refer textbook)
- 24. Kalpana Chawla and Sunitha Williams are two notable Indian-origin astronauts who have worked at NASA. Kalpana Chawla was the first woman of Indian origin to go to space and served as a mission specialist and primary robotic arm operator. Sunitha Williams is another accomplished astronaut of Indian descent who has completed multiple space missions and spent considerable time aboard the International Space Station. Both have made significant contributions to space exploration and research programs conducted by NASA.
- 25. During the night, trees undergo respiration, a metabolic process in which they consume oxygen and release carbon dioxide as a byproduct. Unlike photosynthesis, which occurs during the day and produces oxygen, respiration occurs continuously throughout the day and night. Therefore, during nighttime, trees absorb oxygen from the surrounding air and release carbon dioxide. Anyone who sleeps under a tree at night will be in an environment with reduced oxygen concentration and increased carbon dioxide concentration. This can lead to insufficient oxygen supply to the body, which can cause breathing problems, suffocation, dizziness, and discomfort. Prolonged exposure to such conditions may resul…
- 26. Rhizobium.
- 27. Heavy bags are provided with broad straps to reduce the pressure exerted on the shoulders. Since pressure is inversely proportional to the area of contact, broader straps distribute the weight of the bag over a larger area of the shoulder. This larger contact area results in lower pressure on the shoulders, making it more comfortable to carry the bag. If narrow straps were used instead, the same weight would be concentrated on a smaller area, creating higher pressure and causing discomfort or pain to the shoulders.
- 28. Boron and silicon.
- 29. The different methods of sowing seeds include sowing by hand, using a seed drill, and dibbling. Sowing by hand is the traditional method where seeds are scattered manually across the prepared field. The seed drill is a mechanical device that places seeds at uniform depths and spacing in rows, ensuring better seed placement and reducing seed wastage. Dibbling is a method where individual seeds or groups of seeds are placed in holes made at specific intervals in the soil.
- 30. 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.
- 31. 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.
- 32. The correct hierarchical order of organization from smallest to largest is: Cell, tissues, organ, organ system, organism. A cell is the basic unit of life, tissues are groups of similar cells performing a specific function, organs are structures made of different tissues working together, organ systems are groups of organs functioning together, and an organism is a complete living individual composed of multiple organ systems.
- 33. Artificial magnets are magnets that are made by people in a laboratory or a factory through various methods such as stroking, electrical induction, or electromagnetic means. These magnets are created to have specific properties and strengths according to their intended use. Examples of artificial magnets include horseshoe magnets, bar magnets, U-shaped magnets, cylindrical magnets, disc magnets, ring magnets, and electromagnets. Horseshoe magnets are shaped like a horseshoe and are commonly used in laboratories and industries. Bar magnets are rectangular in shape and are widely used in compasses and educational demonstrations. Electromagnets are created by passing electric current through…
- 34. Girls should take special care of cleanliness and hygiene during the menstrual cycle as it is an important aspect of health and well-being. Making use of disposable napkins or tampons may reduce the chances of infections by maintaining cleanliness and preventing bacterial growth. These products should be changed frequently depending upon the menstrual flow to ensure maximum hygiene and comfort. In addition to using clean menstrual products, girls should wash their genital area regularly with clean water and maintain overall body cleanliness during menstruation. Using clean toilets for defecation is also an important practice during this time. Proper hygiene during menstruation helps preve…
- 35. Baking soda, also known as sodium bicarbonate, has multiple important uses including serving as a fire extinguisher by releasing carbon dioxide when heated, being a key ingredient in the preparation of baking powder, and being used in the preparation of cakes and bread to help them rise and achieve a light texture. Bleaching powder is widely used as a bleaching agent in the textile and paper industries, functions as a disinfectant for surfaces and equipment, and is employed in the sterilisation and purification of drinking water to eliminate harmful microorganisms and ensure water safety. Quick lime, or calcium oxide, is an essential compound used in the manufacture of cement, which is a…