Science-4

Science-4

No. Question Answer 451 What is Googol? Googol is the number one followed by a hundred zeros. 452 Which are the only mammals that can see colours? Man and monkey (apes). It is commonly believed that bulls react violently when they see a red rag. Bulls just cannot see any colour. They react to the teasing movement of the rag. 453 Why does an apple that has been cut open turn brown and then black? Polypnenols in the apple get oxidised. 454 Why does the liquid in the egg become solid when heated or boiled? Due to congealing - coagulation of the yolk. 455 What is the green colour of the leaf due to? Chlorophyll. 456 How many days does Mercury take to complete one rotation on its axis? 59 earth days. 457 What are aerial roots? Roots that grow down from the branch of a tree. The banyan tree is a good example. 458 What is Halley's comet? The Halley's comet is named after the English astronomer Edmund Halley. The theory of gravitation developed by Isaac Newton helped Halley to discover that the bright comet that appeared in 1682 had an orbit that brought it back to the inner solar system at regular intervals. 459 Why is helium used in gas balloons? Because helium is very light and does not burn. 460 What is plastic surgery? Plastic surgery is surgery performed on someone's face or body to remove a deformity or to make it more attractive. 461 How can the moon which is very small, cover the sun which is very big, during an eclipse? The sun is far far away compared to the moon, Therefore even though the sun is very large, the moon can cover it. Even a coin can cover the moon, if held close to the eye. 462 What is the Archimedes Principle? It is a law of physics that states that when an object is totally or partially immersed in a fluid, it experiences an upward thrust equal to the weight of the fluid displaced. The principle is most frequently applied to the behaviour of objects in water, and helps to explain floating and sinking and why objects seem lighter in water. 463 What is meant by a refracting telescope? A refracting telescope is made by using two lenses, both of which are convex. 464 What are corals? They are combined skeletons of tiny marine animals, which live together in a colony. 465 What is the distance between the earth and the sun? About 150 million kilometres. 466 Why does water in an earthen pot become very cool in summer? Earthem pots have tiny holes from which water seaps out to the surface. When this water evaporates, it takes away the latent heat of vaporisation and keeps the pot {and its contents) cool. 467 Why do dogs pant? To keep themselves cool. When they throw out the tongue while panting, the moisture in the tongue evaporates. This directly results in cooling. Humans keep themselves cool by sweating and then evaporation of the sweat, from a large surface of the skin. 468 Which important mineral is to be found in spinach? Iron. 469 What does milking of poisonous snakes mean? It means drawing out poison from the serpents for medical use. 470 Who first isolated Sodium? Sir Humphry Davy. 471 What is a robot? Robot is any machine, developed by man to do the work of a human being such as running a machinery by remote control or to operate devices like switch boards automatically. It is usually directed by sound waves, light waves or radio waves. 472 What is moulting? Moulting takes place because of a number of reasons. Birds discard old feathers for new ones. This is also referred to as moulting. Snakes keep on growing, unlike human beings whose growth stops after attaining adulthood. The snakes discard their skins for a new one. Lobsters, crabs, etc have a hard covering outside the body to support. The animal then breaks out of the old cover and quickly grows before the new chitin already recreated by die tissues underneadi, can harden. Frequently during such periods, the animal hides, since it has no protection then. 473 In which organ of the human body are the lymphocyte cells manufactured? Spleen. 474 Which are the distinct layers of the skin? Dermis and Epidermis. 475 Who invented the printing machine? Johan Gutenburg. 476 Who pioneered the use of antiseptic? Joseph Lister. 477 What is the name of the gland that produces tears? Lachrymal Gland. 478 What is the name of the bacteria that converts milk into curd? Lactobacillus. 479 What does DPT stand for? Diphtheria, Pertussis and Tetanus. DPT is a combined vaccine for diphtheria, whooping cough and tetanus. 480 What does a Hydrometer measure? Density of liquids. 481 Why is the rainbow seen only during and after the rain? This is so because the rain drops serve like prisms and diffract the white light of the sun into violet, indigo, blue, green, yellow, orange and red colours. 482 What is meant by a radio telescope? From their telescopes, astronomers could study objects in outer space that could not be seen with the naked eye. Radio telescopes are telescopes that can study long waves, which are not visible. They can do this using antenna, since radio waves are much longer than light waves. To be effective, radio telescope needs to be much larger than ordinary optical telescope, 483 What is smog? Smog is a mixture of solid and liquid fog and smoke particles. Fog is formed when the humidity is high. The word smog is derived from smoke + fog. 484 What is the name of the layer in the atmosphere of the earth that protects the earth from harmful radiation? The ozone layer. 485 What is the name of the radiation that comes from outer space? Cosmic Rays. 486 For the protection against which disease is the B.C.G vaccination given? Tuberculosis (T.B) 487 What are Sunspots? Areas where the sun's surface is slightly cooler than normal - about 4000 degree C instead of 6000 degrees C. 488 What is the scientific name for Vitamin C ? Ascorbic Acid. 489 Name the galaxy that is nearest to our galaxy. Andromeda Galaxy. 490 Who invented the Barometer? Evangelista Torricelli. 491 Tn the human body what is the end product of protein digestion? Amino acids. 492 Who gave the name rubber to the gum of the Hevea tree? Joseph Priestley. Because the gum could rub oui pencil marks. 493 What are salivary glands? Salivary glands are located in the mouth. There are three pairs, one pair is located in front of the ears, one pair is located underneath the lower jaw and the third is under the tongue. Salivary glands secrete an enzyme called ptyalin, which helps in the digestion of starches. Saliva has an alkaline action. If you see many players chewing gum, it is because when a person is tense, the stomach produces more acids. The saliva, produced by chewing gum, neutralizes this acid. 494 Why do crocodiles shed tears? They secrete the excess salt in die body through this action. They get rid of this by means of a gland near the comer of the eyes. 495 What is Bronze? An alloy of copper and tin. 496 What is the meaning of the word "DINOSAUR"? Terrible lizard. 497 What is Brass? An alloy of Copper and Zinc. 498 Which element is important for the health of bones? Calcium. 499 Which Vitamin helps in preventing rickets? Vitamin D. 500 What is the name for the position of the moon, an earth satellite, when it is at the greatest distance from the earth? Apogee. 501 What is the study of weather and climate called? Meteorology. 502 Name the unit in which electric current is measured? Ampere. 503 What are the four stages in the development of a butterfly? a) Egg b) Larva c) Pupa d) Butterfly 504 Who invented the Radio? G. Marconi. 505 What is meant by Hibernation? Many animals sleep or go into a trance-like state during the long, winter months. This winter sleep is called hibernation. Polar bears go into hibernation in winter. 506 What is meant by Escape Velocity? It is the minimum initial velocity required for an object to escape the gravitational attraction of an astronomical body, and to continue travelling away from it without the use of further effort. 507 Which present day animals are said to be direct descendants of dinosaurs? Komodo dragon and Crocodile. 508 Who invented the military tank? Ernest Swinton of Britain. 509 What is the study of birds called? Ornithology. 510 Who was the founder of the system of medicine known as Homoeopathy? Samuel Hahnemann. 511 From which ore is Aluminium made? Bauxite. 512 How does a plant transfer nutrients it absorbs through its roots to other parts? Through tiny tubes called Xylem. 513 Who discovered the planet Uranus? William Herschel. 514 Kidneys help the body to eliminate waste. Which other parts of the human body do the same? Lungs, skin and rectum. 515 Why is a soap bubble always spherical and not a square or a triangle? When a soap bubble forms and goes up in the air, it is subject to immense pressure from all sides. Only a spherical shape can withstand maximum pressure. That is why soap bubbles are always spherical. 516 Who discovered the circulation of blood in the human body? William Harvey, in 1628. People did not believe in what Harvey said and they opposed his ideas. It took many years for the opposition to die down. 517 What is meant by centrifugal and centripetal force? If a ball is whirled at the end of a string in a circular motion, it would seem as if the ball were suddenly very heavy and pulling harder as it is whirled faster. The force of the string pulling the ball toward the centre is the centripetal force. There is an outward force on the string by the ball. This outward force is the centrifugal force. 518 How much blood does an average adult human being have? About 6.5 litres. 519 Who wrote the book on "The Origin of species by means of Natural Selection"? Charles Darwin. 520 Which is the most destructive insect in the world? Desert Locust. 521 Who invented the sewing machine? EliasHoweofUSAin 1845. 522 What are the substances that can cause cancer called? Carcinogens. 523 What is meant by Photosynthesis? Photosynthesis is the word used for making food from carbon dioxide in the air and water from the soil, in the presence of sunlight. It occurs in plants. 524 What is meant by colour blindness? Inability to distinguish one or more of the primary colours. 525 Who discovered the Laws of Motion? Sir Isaac Newton, 526 Who invented the Telegraph? Samuel Morse. 527 What is a Supernova? A star, which suddenly burns up a lot of its matter and gives a brilliant light. 528 How many chromosomes does a man have in his body cell? 46. 529 Why is selenium used in the making of photoelectric cells? Photoelectric cells convert light into electricity. Selenium is used in making diese cells because its electrical conductivity increases when light strikes it and because it can convert light into electricity. 530 For which invention or process is Henry Bessemer best known? Bessemer converter used for making steel. 531 Who was the first man to study sunspots? A German by name Hienrich Schwabe. 532 Mercury is closest to the sun, then how come Venus is the hottest planet? Venus has thick clouds around it that prevent heat from escaping from its surface. 533 Which planet rotates the most slowly on its axis? Venus 534 How does a microwave oven work? Water molecules vibrate and rub against each other, producing heat because heat is produced by diese molecules an external source of heat is not required for cooking in a microwave. 535 Who produced the world's first petrol driven car? KarlBenz. 536 Why does the running sound of a train change when it passes over a bridge? Sound travels in the form of waves. The frequency of the waves and die amplitude (the width) of the waves determine the sound. The sound waves are of different kinds, when a train moves on solid ground, and when it moves on a bridge, whether made of steel or plain concrete. 537 What is a photometer? An instrument for measuring the intensity of light. 538 What is meant by Radio carbon dating? Scientists describe the radioactivity of an element in terms of half-life - the time the element takes to lose half of its radioactivity through decay. By measuring the radioactivity scientists can calculate the age of the element that is being tested. 539 What is the meaning of geothermal energy? The heat produced witiiin the crust and upper mantle of the earth, primarily by decay of radioactive elements. 540 What is the difference between nuclear fission and nuclear fusion? The reaction where heat is produced because of the fission (division) of a nucleus is called nuclear fission. The reaction in which heat is produced because of the fusion of two nuclei is called nuclear fission. In hydrogen bomb die reaction was due to nuclear fusion. In the atomic bomb dropped on Hiroshima and Nagasaki, it was a fusion bomb. 541 What is Robert Boyle known for? Boyle is known for his experiments on the physical properties of air and his law on the relationship between the pressure and the volume of the gas. 542 What is genetics? Genetics is the study of all those qualities of organisms that are governed by certain biologically active elements derived from the parents. 543 How many toes does an ostrich have on each of its legs? An ostrich has two toes in each leg. 544 Who is considered to be the father of modern astronomy? Copernicus. 545 From which material is aluminum made? Bauxite. 546 What are asteroids? Asteroid means "like star". Asteroids are heavenly bodies like the earth, but very much smaller in size. Some may be only a kilometre or two in diameter. They also orbit around the sun. 547 What is meant by convection of heat? A process in which heat is transferred by movement of heated fluid such as air and water is called convection. 548 What is meant by cloud seeding? Spraying of certain chemicals into clouds to induce rain. 549 Who was the first man to point out that things get spoiled because of germs? Loius Pasteur. 550 Why does cutting onions give a burning sensation in the eyes? When onions are cut, volatile oils, containing sulphur, are released. In combination with the water in the eye, they produce irritation. 551 What is the enzyme in human saliva? Mainly Amylase, which converts starches anc glycogen into the sugar maltose. Apart from saliva amylases are found in pancreatic juices and intestinal juices too. 552 What is meant by ignition point? Ignition occurs when the temperature of a substance is raised to die point at which its molecules will read spontaneously with oxygen, and the substance begin; to bum. This is called the ignition point. 553 Which is the largest and heaviest snake in the world? The anaconda. It weighs upto 200 kg. 554 To which family of plants do bamboos belong? The grass family. 555 Who propounded the theory of relativity? Albert Einstein. 556 How does the chameleon catch its prey? It flicks out its long sticky tongue and catches unwary insects flying by. 557 What is concrete? How is it made? Concrete is a rock like substance made from cement, natural sand, stone and water. Cement and water react chemically and serve like glue to bond the stones and form a hardened mass. When the material is still in a "plastic state" it can be very easily formed into various shapes. But once the concrete sets (hardens) no changes can be made. 558 In which part of their body do spiders spin the thread? Abdomen. 559 What is meant by fermentation? Breakdown of organic substances into simpler substances due to the action of bacteria is called fermentation. Grapes are fermented to produce wine. Thus fermentation of wheat and rice results in the breakdown of the starches to simpler sugars and alcohols. 560 In which part of the plant are ovules contained? Pistil. 561 How long do butterflies live? 2 to 3 weeks. 562 What is the study of prehistoric animal and plant life through the analysis of fossils called? Palaeontology. 563 What does mammal mean? A mammal is a warm-blooded animal, which suckles its young ones with milk and has hair on its skin. 564 Which are the main gases in the atmosphere of the earth? Nitrogen and oxygen. 565 Who invented the stethoscope? Laennec. 566 What is a huge mass of ice slowly moving ahead called? Glacier. 567 What is an ammeter used for? Measuring the strength of an electric current. 568 How do bats communicate with each other? Bats produce screeching sounds. As these sounds strike objects around them, they produce echoes, which are heard by the bats. This helps the bats in navigation. Human beings cannot hear the sounds produced by the bats as they have much higher frequency than the audible range of the human ear. 569 What are the three main constituents of a galvanic cell? a. An anode b. A Cathode c. An electrolyte in which the anode and cathode    are placed. 570 Who invented the telephone? Alexander Graham Bell. He was, however, interested in constructing an electrical device that would help deaf-mutes learn to speak. 571 What is the fluid part of the blood called? Plasma. It is about 90% water. 572 What is malaria? Malaria is an acute disease caused by an animal parasite called plasmodium. The disease is spread by the bite of the female Anopheles mosquito. 573 What is the origin of the word 'Malaria' ? Romans were familiar with this disease. They thought it is caused by bad (mal) air (aria). 574 How many eggs does a starfish lay at a time? Millions. 575 What does the acronym RADAR mean? Radio Detection and Ranging. 576 What is meant by Diabetes? Diabetes is caused because of inadequate secretion of insulin by the pancreas or the inability of the body to utilise the insulin produced. 577 How does the sun generate its energy? Inside the sun a reaction similar to that of a hydrogen bomb goes on continuously. Two atoms of hydrogen fuse to produce an atom of helium. The sun is today at the midway of its life. 578 What is the meaning of the word 'Protozoa' ? Protozoa means the first animal. They are the simplest form of life. They are made of a single cell. 579 What is the difference between dyes and pigments? Dyes are complex organic substances that are chemically bound to the fibres. Pigments consist of larger particles that form a film on the surface. 580 Who proposed the Centigrade Scale? Anders Celsius first proposed the centigrade thermometer, which has a scale of 100 degrees separating the boiling and freezing points of water. 581 Why do flocks of swans fly in a V-formation? By flying in this way they meet minimum resistance from the air to their flying. 582 Which is the fastest moving land snake? The Black Mamba, which has a speed of about 11 km per hour. 583 What is meant by the term habitat? Habitat is the place where a certain animal or plant would live and grow naturally. Thus an ocean is the habitat of whales and a pond is the habitat of frogs. 584 How can astronauts walk in space without any support to walk on? Because there is hardly any gravity far away from the earth. (Or any heavenly body). 585 Who is usually considered to be the discoverer of oxygen? Joseph Priestley. 586 What is a Tapir? Where is it found? A Tapir is an animal that looks like a pig. It is found in Malaysia and Central and South America. 587 Why are tea plants cut when they grow to a height of two metres or more? To force more tender leaves to branch out and make handpicking of leaves easier. 588 What is forging? The shaping of metals by hammering them is called forging. 589 What was Chandrasekhar Subrahmanyan known for? Indian-born American theoretical astrophysicist and Nobel laureate, Chandrasekhar Subrahmanyan contributed greatly to our understanding of the evolution of stars. Chandrasekhar was best known for his theoretical prediction, made at the age of 20, that large stars would collapse at the end of their lives into some unknown state even more dense than that of a white dwarf. 590 What is the condition caused by lack of Vitamin C? Scurvy.s 591 Who was the first man to make a phonograph (gramophone)? Thomas Alva Edison. 592 What is a black hole? A body whose mass is so intensely concentrated that even light cannot escape its gravitational attraction. Normal properties of space in its vicinity are altered drastically. 593 How did Charles Goodyear discover the vulcanisation of rubber? Accidentally he spilled a mixture of rubber and sulphur on a hot stove. He observed that the rubber had become stronger and elastic. From there he got; the idea of hardening rubber. 594 How did Roentgen discover X-rays? While experimenting with a glass tube from which the air had been pumped, Roentgen happened to pass an electric current through the tube. Nearby was a screen coated with Barium Platinocyanide. Suddenly he noticed that the screen was glowing with a greenish blue light. After experimenting with this radiation, coming from the evacuated glass tube Roentgen found that this radiation could pass through substances of varying densities placed between the tube and the screen. He named these rays X-rays. 595 What are chromosomes? Chromosomes are tiny thread-like parts of a cell. These can be seen under a microscope. They are made up of smaller parts called genes. These chromosomes and genes decide heredity. 596 Who was the first person to show that the Milky Way is composed of stars? Galileo Galilei. 597 What is the average life of a red blood corpuscle? 120 days. 598 What is the scientific study of insects called? Entomology. 599 What are the properties of aluminium, which make it very useful, particularly in the aerospace industry? Aluminium is very light and yet very strong. It does not get corroded. Aluminium's excellent electrical conductivity makes it very useful in making high voltage electrical conductors. 600 Who invented the Battery? Alessandro Volta.