Science-3

Science-3

No. Question Answer 301. Who first discovered that water was produced by burning hydrogen? Henry Cavendish. 302. What are the parts of a comet? Nucleus, coma and tail. 303 Why are the blades of the fan slightly curved? If you wish to carry sand or any solid substance from one place to another, you can carry little if there are straight metal strips. A pail can carry much more. In the case of air, which is a fluid, a slightly curved blade is enough to help circulate air in the room. 304 What is absolute zero temperature? Absolute zero is the temperature at which thermal energy (energy related to heat) vanishes. It corresponds to -273.15 degrees, on the Celsius scale. 305 Who is considered the father of plastic surgery in ancient India? Sushruta. He is best known for the operations he performed called rhinoplasty (remodelling of the nose). 306 What are isotopes? Isotopes are different forms of an element with the same number of protons, but a varying number of neutrons in the nucleus of an atom. All elements consist of atoms. Atoms have a nucleus, which consists of proton or protons and neutrons. They usually have as many electrons as protons, continuously whirling around the nucleus. Hydrogen has two naturally existing isotopes - one with only a proton and no neutron in its nucleus and another with a neutron and a proton. The first one is commonly known as hydrogen. The second one is rare and is called deuterium or heavy hydrogen. A third isotope, called tritium, is artificially produced. Tritium has one proton and two neutrons. 307 Who discovered the cause of malaria? Ronald Ross. 308 Which planet has a moon named Titan? Saturn. 309 Name the largest bone in the human body. Femur (in the thigh). 310 What is the source of all energy on earth? The sun. 311 What was the name of the instrument used by Jagadis Chandra Bose to measure sensitivity of plants? Crescograph. 312 How long do banyan trees live? Banyan trees seem to live for hundreds of years. Aerial roots develop from its branches and they take root in the soil. Over the years these roots turn into sturdy trunks, which too grow roots and the cycle continues. It is said that the entire army of Alexander had taken shelter under one such banyan tree. 313 Which part of the plant do you eat when you eat carrots? Roots. 314 Who was the first man to travel in space? Yuri Gagarin. 315 What is reinforced concrete? Reinforced concrete is ordinary concrete which has steel rods fixed in it. 316 What is meant by latent heat? Heat absorbed when a substance changes its state without changes in temperature, e.g. water boils at 100°C. When we heat it further the temperature is not raised but the heat is absorbed. 317 In ancient India shells of a sea-animal were used as money. What were they called? Cowries. 318 How does spraying kerosene on marshes reduce mosquitoes? A film of oil is produced which prevents the larvae of the mosquitoes from having access to the oxygen in the atmosphere. 319 How many bones are there in an adult human being? 206. 320 Who is considered to be the father of Geometry? Euclid. 321 What is the study of sound called? Acoustics. 322 Which was the first satellite India launched from Indian soil using an Indian launch vehicle, SLV3? Rohini Satellite (RSI). 323 What are bacteria? Where are they found? Bacteria formerly classified as plants are now classified separately as Prokaryotes. They are so small that we can see them only with a microscope. They are found almost everywhere. Bacteria cause and spread diseases, but there are many bacteria that are helpful to man. Bacteria are responsible for converting grape juice into wine and milk into curd. 324 What is the name of the instrument that records heart beat? Cardiograph. 325 Who discovered the connection between magnetism and electricity? Hans Christian Oersted. 326 Who discovered the presence of neutrons in the nucleus of elements? Physicist James Chadwick. 327 At what temperature does water become ice? Zero degrees on the Celsius scale. 328 What do deciduous trees mean? Trees that shed leaves in autumn are called deciduous trees. 329 The electric discharge of which fish is the most powerful? South American Electric Eel. 330 What is the name for power generated from water? Hydroelectricity. 331 How is sound produced? Basically sound is produced when a vibrating body sets air molecules in motion. Musical instruments produce sounds by vibrating strings. The vibration and waves that are produced reach the ear, which passes the vibrations to the brain. To test this take a steel tumbler and tap on it with a metallic spoon. Sound is produced. Hold the edge of the tumbler between two fingers. The sound stops. This illustrates the importance of vibration in producing sound. 332 How are motion pictures made? When the eyes see an image, they hold onto it in the form of a visual memory for a fraction of a second after it is gone. In a motion picture, the projector flashes still pictures quickly in succession. The usual numbers of pictures that are projected per second are 24. Because of persistence of vision, the picture seems to be one continuous moving picture. 333 From which part of the plant, is ginger that we eat obtained? From the stem. 334 Who was the first person to find out that microscopic organisms are responsible for milk, wine, etc turning sour? Louis Pasteur. 335 What is the meaning of the word Hippopotamus? River Horse. 336 Who invented the Hovercraft? Christopher Cockerell. 337 Who discovered Vitamins? Christopher Eijkman - though he did not use the word, vitamin. 338 Who coined the word Vitamin? CasimirFunk. 339 Why does the planet Mars appear red? Due to the highly oxidised surface of the planet. 340 Name the Vitamin that prevents night blindness. Vitamin A. 341 Where do sea plants obtain carbon dioxide to manufacture their food? From dissolved gases 342 Who is considered as the father of modern Medicine? Hippocrates. 343 How does an Octopus camouflage itself? By changing its colour and merging with the background. 344 Who first proved that lightning is an electric charge coming down to the earth? Benjamin Franklin. 345 What are cosmic rays? Cosmic rays are radiation from outer space, which bombard the earth. They constantly strike the molecules of the earth's upper atmosphere. As a result, additional radiations are produced. The atmosphere absorbs most of these rays. 346 What is a cocoon? It is a silk case, that covers a caterpillar before it becomes a moth (butterfly). After the caterpillar is completely wrapped in its cocoon, it sleeps through the winter. 347 What does the acronym LASER stand for? Light Amplification by Simulated Emission of Radiation. 348 How is cement obtained? Heating a mixture of limestone and clay. 349 Name the only mammal, other than man, that can walk upright? Gibbon. 350 Which disease is caused by insufficiency of iodine in the diet? Goitre. 351 What are molluscs? A class of animals with a soft body and no bones. 352 Which animal has the longest life span? Tortoise. 353 How is the glow of a firefly caused? When certain proteins get oxidised, in the presence of an enzyme called luciferase, light is produced. Fireflies have special light organs on the underside of the abdomen. Here in the presence of luciferase, light is produced. 354 Who first enunciated the laws of heredity? Gregor Johann Mendel 355 What does the acronym, SONAR, stand for? Sound Navigation and Ranging. 356 What are comets? Comets are heavenly bodies that travel around the sun. When they are near the sun, they look like stars with long glowing tails. Halley's comet appears once in about 76 - 78 years. Some comets appear near the sun only once in millions of years. A comet has a head, which looks like a star. The head is surrounded by a coma or a fuzzy hood. The tail may be millions of kilometres long. 357 Why does a metal rod feel cooler than a piece of wood? Metals are good conductors of heat. When we touch a metallic rod, it takes away the heat from the hand and feels cooler. A piece of wood is a bad conductor of heat and therefore it does not take away the heat from our hands. 358 Why does a jet of water come out of a whale's back? It is air, exhaled by the whale. 359 How many teeth do sheep have on their upper jaw? None. 360 How are helicopters useful in rescue operations? A helicopter can move up, take off or land easily from small clear areas. Hence they are useful in dropping food or rescuing stranded people. It has a rotor, which enables it to rise up or go down, vertically. 361 How can lizards walk on walls? The base of their paws has cuplike structures that stick to the walls. This enables them to move even on walls. 362 How does a perfume spread to the corners of any room even though there is no breeze? Molecules of oxygen, nitrogen and other gases in the air keep on spreading all around them. 363 Where does light fall inside the eye? Retina. 364 Chlorine is very injurious to health. So is sodium. The table salt we use is sodium chloride. Why is it not dangerous to health? It must be noted that a compound formed from two or more elements need not have a single property of its constituent elements. Sodium and Chlorine combine to form table salt, which is healthy (in small amounts). Water, which sustains life, is formed from hydrogen and oxygen. The properties of hydrogen as well as oxygen are not found in water. 365 How does a frog breathe under water? Through its skin. 366 What is the difference between a tortoise and a turtle? Tortoise is the name applied to the terrestrial species and turtle is the name applied to the aquatic species. 367 What is meant by sublimation in chemistry? Conversion of a substance from solid state to vapour state (without the intervening liquid state) is sublimation. For example, iodine sublimates from its solid state to vapour. 368 What are the sieve like plates in a whale's mouth called? Baleens. 369 Why do people cover ice slabs with sawdust? Sawdust is a bad conductor of heat and slows down the melting of ice. 370 Why are droplets formed on the outer surface of a glass when cold water is poured into it? The moisture in the air condenses on the cool outer surface of the glass. 371 Why is food preserved in a refrigerator? Most bacteria are destroyed as the temperature of the surroundings rises. Temperatures higher than 40° C do not favour growth of bacteria. Similarly low temperatures prevent bacteria from multiplying. Hence food is preserved in the refrigerator by keeping its contents at low temperature. 372 Why do we feel sleepy after a heavy meal? The blood circulation to the digestive tract increases. As a result the blood circulation to the brain is reduced. This makes us sleepy. 373 Which organs in the human body filter waste products from the blood? Kidneys. 374 Which organs are most damaged when a person consumes much liquor? Liver and stomach. 375 What does Aurora mean? Bright patches of light are seen at high latitudes above 60° north or south. They are named Aurora Borealis (northern lights) or Aurora Australis (southern lights) depending on their position. The term "Aurora Polaris", polar lights, is a general name for both. The aurora consists of rapidly shifting patches and dancing columns of light of various hues. 376 Which vitamins are soluble in water? Vitamins of the B and C group. 377 What is the composition of perspiration? Mostly water with a little salt. 378 Which gland in the human body produces insulin? Pancreas. 379 What is the principal enzyme in the gastric juice? Pepsin. 380 What is the vaccination given to prevent polio? Salk Vaccine. It was discovered by Jonas Edward Salk in 1952. The theory behind the Salk Vaccine is that a virus that has been killed cannot infect or multiply, but it can still produce antibodies against that particular virus. The vaccine was tested first on monkeys and eventually on children, including Dr. Safk's three children, before it was released for nationwide distribution. 381 What are Pachyderms? Animals with thick skin like elephants and rhinoceros. 382 Why is it that some people have a dark skin? The dark colour of the skin is due to a pigment called melanin. On exposure to sunlight, man's skin undergoes gradual tanning to protect the skin from injurious solar rays. 383 Which Vitamin helps in preventing rickets? Vitamin-D. 384 Which is the second most common element on the earth's surface? Silicon. 385 Which planet is known as the red planet? Mars. 386 What does a lizard do when its life is in danger? The lizard discards its tail to divert the attention of its enemy. 387 Why is the housefly considered a health hazard? On their legs they may carry millions of germs. When they rest on a food plate, these may be transferred to the object they rest on. 388 Which metal is also called quicksilver? Mercury. 389 What is the main food of a Koala bear? Eucalyptus leaves. 390 If hair is dead tissue, how does it grow? It is true that hair consists of Keratin, a dead tissue. But the hair is lodged in a follicle located a little below the scalp, which is very much alive. This is where the growth takes place. The living hair pushes up the dead tissue. That living tissue also dies and is pushed up. Pull out a hair and you will feel pain and understand the truth of this statement. 391 What is meant by Acid Rain? When there is a substantial amount of sulphur dioxide, carbon dioxide, etc in the rain, it is referrec to as acid rain. 392 What is the common food of the Blue Whale? A shrimp like creature called krill. 393 What is Betelgeuse? It is one of the brightest stars visible in the night sky, It is in the constellation, Orion. It is also called Alpha Orionis, It takes about 300 years for the light from Betelgeuse to reach the earth. 394 How long do elephants live? 65 to 100 years. 395 What do a koala bear, opossum, wombat and bandicoot have in common? They are all Marsupials, i.e. they carry their young ones in pouches. 396 Name the person who first discovered the presence of Microbes. Anton Van Leeuwenhoek. 397 How do mother animals recognize their babies? By their smell. 398 Why do water pipes burst in hill stations? There is an unusual expansion of water, when its temperature goes below 4° C. Instead of contracting, the water begins to expand till ice is formed at zero degrees Celsius. Unable to bear the pressure, the pipe bursts. 399 Which animal shoots its quill and hurts the enemy? Porcupine. 400 Who made the first electric motor? Michael Faraday. 401 Who first used electrolysis for isolating elements? Sir Humphry Davy. 402 Who first put forward the Atomic Theory that all matter is made of atoms, held together by some force of attraction? John Dalton. 403 Is it true that the age of a tree can be known by studying its rings? Yes, each year during spring a light ring grows just inside the bark of the tree. During summer and autumn, the ring that grows is darker. Too little sunlight, too little moisture or injury results in a smaller and darker ring. After counting the rings, we can assess the age of the tree. 404 How does the rotation and revolution of the earth affect our lives? The earth rotates on its axis even while it revolves around the sun. The rotation results in night and day. As the earth revolves around the sun, it also tilts on its axis. This tilt causes changes in the earth's position, which results in the seasons. 405 Who found out that oxygen is present in both water and air? Antoine Lavoisier. 406 Which Vitamin is important for the health of bones? Vitamin D. 407 Why do animals like rats and squirrels keep gnawing at things? Gnawing helps wear down their teeth. If they did not gnaw at things their teeth would keep on growing. 408 Who was the first woman of Indian origin to travel in a space vehicle? Kalpana Chawla. 409 Why does a snake flick its tongue so often? To smell the surroundings. 410 What is the scientific name for man? Homo Sapien. 411 Who is considered to be the father of modern experimental science? Galileo Galilei. 412 What is the name of our galaxy? Milky Way. 413 How is petroleum formed? Remains of plants and tiny animals that lived millions of years ago remain buried and turn into petroleum. 414 What is a mirage? How is it caused? A mirage is a reflection, caused by the bending of light rays. When we ride along highways particularly in arid regions, we see a reflection ahead, which looks like water. This is caused by a dense layer of warm air near the surface of the earth. Light rays from the sky are reflected toward one's line of vision - what one sees is a reflection of the sky and not water. 415 How is oxygen formed in the atmosphere? In the presence of chlorophyll, a chemical reaction takes place in the leaves using carbon dioxide in the air and water transported from the roots. As a result of the chemical reaction, starch is produced. Oxygen is the by-product of this reaction. 416 Which is the juice secreted in die liver which helps digestion? Bile. 417 What is meant by the word 'frequency' of a sound? Frequency is defined as the number of vibrations per second. It must be noted that sound is caused as a result of vibrations in air columns or strings or objects. Sound travels in waves. 418 Which is the longest poisonous snake in die world? King Cobra 419 What is the tendency of plants to grow towards sunlight called? Phototropism. 420 Why do snakes shed their skin? Unlike human beings, whose growth stops around 20 years, snakes keep on growing. This becomes possible because they keep casting off old skin and develop new skin, when the old one is shed. 421 Why does it take longer to cook food at high altitudes? The atmospheric pressure at high altitudes is much lower than at sea level. The greater the pressure, the faster the cooking. 422 What is the use of the ozone layer in the earth's atmosphere? It bounces off ultraviolet radiation. 423 How do we get heat and light from the sun? Through radiation. 424 How do insects breathe? Insects breathe through the tiny holes in their body. 425 Why doesn't ice sink in water? Ice is lighter than water. After the temperature of water cools down to 4° Celsius (instead of contracting) water keeps on expanding till it reaches 0° Celsius and becomes ice. 426 Apart from earth on which other planet in the solar system does life exist? Nowhere else. As we know it. 427 What is meant by the Water Table? Water filters down the surface of the ground and is absorbed and stored by soil and rocks in a zone of saturation. The top of this zone is called Water Table. During drought, the Water Table too goes down. 428 Who is known as the father of computers? Charles Babbage. 429 Why do we feel hungrier in winter? In winter we need energy to maintain the body temperature in addition to sustaining normal activities of the body. To meet this requirement of energy we eat more. 430 Can you give ah example of reflex action? Knee jerk. It is the involuntary kick caused by a blow on the tendon just below the knee. 431 What is an electrocardiograph? The electrocardiograph is an electrical instrument, which records the activity of the heart muscle. As the heart beats, several activities take place in a regular! order. The electrocardiograph records changes that occur in a regular order, during a complete heartbeat. 432 Which bird can rotate its head by 180 degrees on either side? The Owl. 433 Man, dogs, cats, horses have lungs through which they breathe. How do smaller animals like fish, earthworm, etc obtain their requirement of oxygen? Earthworms also respire. They use their moist skin to exchange carbon dioxide for oxygen. The fishes use their gills to respire. Even frogs in the tadpole stage use their skin for respiring. Reptiles such as snakes and turtles and even birds breathe through lungs. 434 What are the uses of snake venom? It is helpful in curing many ailments affecting the nervous system. 435 What is the major element a star is made of? Hydrogen 436 Where does a female butterfly lay its eggs? Under side of leaves. 437 Who invented the miner's safety camp? Sir Humphry Davy. 438 Name the world's largest rodent and where is it found. Capybara found in the Amazon jungles of South America. 439 What is the chemical name of baking soda? Sodium Bicarbonate. 440 What is Telepathy? Telepathy is direct communication of thought from one person to another, without using any physical channels of communication. Though there are many who claim telepathy is possible, there has been no positive proof of the existence of telepathy. 441 What is ultrasound? Human beings cannot hear sound waves which have frequencies above 20,000 vibrations per second. This is termed ultrasound. 442 Who was the scientist who initiated the Atomic Energy Programme of India? Homi Bhabha. 443 Who invented the rigid airship? Ferdinand Von Zeppelin. 444 Who invented the calculator? Blaise Pascal. 445 From which element was the first Atom Bomb made? Uranium 235. 446 Who invented the diesel engine? Rudolf Diesel. 447 Who made the first locomotive that had successful runs? George Stephenson. 448 What is paper made of? Mainly wood pulp. 449 Name the Chinese method of curing ailments by using needles? Acupuncture. 450 What causes rusting? How can it be prevented? Metals like iron are often exposed to moisture. Rusting is the process of oxidation occurring when the iron and air slowly combine to form iron oxides. Oil is often used to slow down rusting. When a coat of paint or varnish is given to a metal, this also prevents (reduces) oxidation.