1. When and why are days longer in the northern hemisphere as compared to those in the southern hemisphere on earth?During 21st March till 23rd September. The reason for this difference inthe lengths of a day is that the earth’s axis of Rotation is tilted withrespect to its plane of revolution around the Sun which is also the reasonwhy different seasons occur on earth. As you can guess the oppositeHappens during the remaing six months of the year for the same reason
2. What is the difference between a sea breeze and a land breeze and when do they occur?Few hours after the sun rise as the land gets hot ,the air just above startsmoving upwards and lets the cool air over the sea move towards the landand the breeze so set in is called the sea breeze. Similarly towards theevening as the land gets cooler faster than the sea, the air over the seamove upwards due to convection and the cool air over the land movedownwards towards the sea producing the land breeze
3. What is the structure of earth’s atmosphere, and what is the purposeof ozone layer?The earth’s atmosphere consists of the Troposphere, the Stratosphere,the Ozone Layer, the Mesosphere and the IonosphereThe Ozone layer prevents the UV radiation from reaching the earth’slower regions and thus protect the life on earth
4. What is greenhouse effect and what is the main cause for it?The heating of the earth’s lower atmosphere due to the absorption ofthe earth emitted IR radiation by certain gases is called the greenhouseeffect. Most common gases responsible for the effect arecarbon di oxide and methane
5. What is smog and in which part of the year is it maximum?Smog is a combined word for SMOKY-FOG. It appearsmostly in wintry days due to burning of large amounts ofcoal. It is hazardous as it is a combination of smoke andsulfur di oxide. In colder weather the water vapour in theatmosphere condenses and thus becomes a blanketpreventing the air moving upwards.
6. How can you show that light needs no medium to travel but sound requires a medium?If you keep an electric bell with a small lighted bulbin a Jar and slowly create vacuum inside the jar,nothing happens to the light from the bulb but thesound of the bell slowly diminishes and finally diesdown. Also we know that the sunlight reaches uson earth without any problem even though the inbetween space is empty. Sound needs a medium asit is directly related to the compression andrarefaction of the medium that travels as soundwaves
7. Why does the image formed in a pinhole cameraappear inverted?Because the light travels along straight line
8.If you keep two plane mirrors inclined at anangle of 600 and place an object in the middlehow many images do form? FIVEThe formula forfinding the numberof Images isN = (360 / ang btwnthe mirors)-1
9.What is the difference between a real and a virtual image? What is the image formed when you stand in front of a plane mirror?If the reflected rays meet at a point on the same side of the object onlythen a Real image is formed. If the reflected rays appear to meet at apoint behind the mirror then the image is said to be virtualThe image formed in a plane mirror is Virtual Mirror Image object
10.What is the nature of the image formed by a concavemirror when the object is placed beyond the centre ofcurvature and where is the image formed?The image is Real, Inverted and Smaller than the object.It is formed between the Focus and center of curvature
11.How are the states of matter related to the arrangement of moleculesin a given substance? And why are they so arranged?Molecules are very closely packed in solids, loosely packed in liquidsand are somewhat free to move around, while in gases they arecompletely free to occupy all the available space, with the intermolecular forces being least. This arrangement depends entirely ontheir kinetic energy, which changes with the addition or subtraction ofthe heat energy ,which is the most important agency for change of stateof substances
12. If you keep equal amount of hot water at thesame temperature in three different vessels onemade of steel, one of copper and the other ofplastic all exposed for an hour in the open shade,which will cool faster and why?The one in the copper vessel cools fastestas the heat is lost both by conduction andconvection. Next is steel because it takeslittle more time to cool as compared tocopper. The one in the plastic vessel cannotlose heat by conduction and thus remainshot for longest time
13.In winter why does one wear a woolen sweater to keep oneself warm? Instead if you wear two cotton shirts will it have the same effect?Woolen wear shields heat from escaping from thebody and thus the body keeps warm.Cotton being made of cellulose fibre lets air passthrough more easily and thus loses body heat tooutside and thus cannot keep you as warm aswoolens
14.How does Solar heat reach the earth though the in between space is empty of matter?The heat from the sun comes through theelectromagnetic radiation particularly inThe IR wavelength and thus does not requireany medium to travel
15. What is convection? How can you demonstrateit to your buddy?Convection is the mode of transfer of heat in fluids
16.What are lithosphere, hydrosphere and biosphere?Lithosphere is the solid part of the earth consisting of thecrust and the upper mantle; Hydrosphere is the part of theearth covered by water and Biosphere is the entire globeconsistIng of all forms of life starting from the bottom ofthe oceans upto the atmosphere.
17. Explain the process of photosynthesisPhotosynthesis is the process by which plantsproduce food by combining water,Carbon di oxideand nutrients by the action of sunlight six molecules of water plus six molecules of carbon di oxide produce one molecule of sugar plus six molecules of oxygen
18. Why is the shade of a tree much cooler thanthe shade of a building?The shade of a tree is cooler because of the release of watervapour by the leavesduring transpirationkeeps the surroundingat lower temperaturethrough the absorptionof heat by watermolecules
19. Why are flowers colourful and sweet smelling?The colours and sweet smells of flowers is anatural device of the plants for attractingInsects like bees, butterflies and birds to siton them and carry the pollen grains to otherflowers of the same type for pollination
20. What are the main roles of roots in plants?The main role ofroots in a plantis to absorb waterand other nutrientsfrom the ground asalso to give stablesupport to the plant
21. What does one mean by electronic configuration?Explain with an exampleElectronic configuration defines the structure of atoms with the distribution ofElectrons in their orbitals (shells) following the simple rule that there can beonly 2n2 electrons in a given orbital with number n. For example if we considerthe element Oxygen which has the atomic number 8, the electrons are soarranged that, there are 2 in the first shell and 6 in the second shell. Oxygen (2,6) Copper (2,8,18,1) Gold (2,8,18,32,18,1)
22. What happens to an atom when it loses an electron?Atoms are always neutral, meaning the the number ofpositive charges (protons)should be equal to the numberof negative charges (electrons). Hence if an atom loosesan electron there will be a charge imbalance and the atomis said to be ionised and becomes a positive ion. Similarlywhen atom captures an electron then again the atom isionised and this time it will become a negative ion
23. What is the difference between a mixture and a compound?A mixture can be separated physically whereas a compoundcan be separated only chemically. A mixture will not haveany molecular bonding, but a compound always hasmolecular bonding. A suspension of flour in water, Sodium Chloride crystal a heterogeneous mixture
24. What happens when an acid reacts with a base?When acid reacts with a base the resultant products area salt and water. Acids When acids dissolve in water they produce hydrogen ions, H+. For example, looking at hydrochloric acid: HCl(aq) -> H+(aq) + Cl-(aq) Alkalis When alkalis dissolve in water they produce hydroxide ions, OH-. For example, looking at sodium hydroxide: NaOH(aq) -> Na+(aq) + OH-(aq)Neutralisation reactionWhen the H+ ions from an acid react with the OH- ions from an alkali,a neutralisation reaction happens to form water. This is the equation for the reaction:H+(aq) + OH-(aq) ->H2O(l) If you look at the equations above for sodium hydroxide and hydrochloric acid you will see that there are Na+ ions and Cl- ions left over. These form sodium chloride, NaCl.
25. Why do you have to add some salt to water to make it conduct electricity effectively?Pure water is a very poor conductor of electricity as the self ionisationof water is a very slow and ineffficient process. If we add a salt or someacid or base which are electrolytes water splits them into the positiveand negative ion of the compound by breaking the ionic bond and thesefree ions can now conduct electrical current very well. Only then theseperation of water into hydrogen and oxygen becomes possibleIn the water at the negatively charged cathode, a reduction reaction takesplace, with electrons (e−) from the cathode being given to hydrogen cations toform hydrogen gas: Cathode (reduction): 2H2O(l) + 2e− → H2(g) + 2OH−(aq);At the positively charged anode, an oxidation reaction occurs, generatingoxygen gas and giving electrons to the anode to complete the circuit: Anode (oxidation): 2H2O(l) → O2(g) + 4H+(aq) + 4e−;Combining these two reactions yields the overall decomposition of water intooxygen and hydrogen: Overall reaction: 2H2O(l) → 2H2(g) + O2(g)
26.A can finish some work in 6 days. If B is 50% moreefficient than A in how many days will he finish the samework? In four daysIf the efficiency of A is 1 , that of B is 1 and half = 3/2Time taken by B = 6 divided by 3/2 = 6 . 2/3 = 4
27. In a class of 20 students, if 12 take French and 15 take German , how many are doing both? SevenNumber of students taking other languages 12 + 15 = 27As there are only 20 students 27 – 20 = 7are taking both French and German
28. If two apples and four pears together cost Rs 22,but a single apple is only Rs 5, what is the cost of a pear? Rs Three 2 A + 4 P = 22 , A =5 Therefore 10 + 4 P =22 which means 4P = 12. Hence P=3
29. If Alistair loses 5 kgs weight and Ishan gains 5 kgs what happens to the average age of the two? Remains the same A=X I =Y Average = (X+Y)/2 A = X–5 I = Y+ 5 Average = (X+ 5 +Y -5)/2 = (X + Y) / 2
30.In a right angled triangle if one of the angles is 350, what is the measure of the other angle? 550 A right angled triangle has one angle to be 900 Of the other two one is 350. Sum of the three angles of ANY triangle is 1800 Hence the measure of the third angle is 1800 – (900 + 350) = 550
31. Which is the brightest natural object in the night sky? Planet VENUS
32. Who invented the microscope? Leeuwenhoek was inspired byAnton Van Leeuwenhoek the glasses used by drapers to inspect the quality of cloth. He taught himself new methods for grinding and polishing tiny lenses of great curvature which gave magnifications up to 270x diameters, the finest known at that time. These lenses led to the building of Anton Van Leeuwenhoeks microscopes, and the biological discoveries for which he is famous. Anton Van Leeuwenhoek was the first to see and describe bacteria (1674), yeast plants, the teeming life in a drop of water, and the circulation of blood corpuscles in capillaries.
33. What is sericulture?Sericulture is the practice of rearing silkwormsFor the production of raw silk.Silk-fibre is a protein produced from the silk-glands ofsilkworms.Historically, sericulture was introduced for the firsttime, into China by Hoshomin, the Queen of China.For a long time, sericulture was considered to be anational secret by the Chinese Government, and as anindustry it was not known in other countries. Later, itwas introduced into Europe and Japan as well.According to reports available, sericulture wasintroduced into India about 400 years back and theindustry flourished as an agro-industry till 1857, withan annual production of two million pounds of silkfibre.
34. What was CHIPKO movement?CHIPKO movement was the first active participation of villagersparticularly the women against felling of trees by timbre contractors inthe Himalyan region. As the name suggests, women hugged the treeswhen people came to axe them which indeed prevented the felling oftrees.The first Chipko action took place spontaneously in April 1973 and overthe next five years spread to many districts of the Himalaya in UttarPradesh. The Chipko protests in Uttar Pradesh achieved a major victoryin 1980 with a 15-year ban on green felling in the Himalayan forests ofthat state by order of Indias then Prime Minister, Indira Gandhi. Sincethen the movement has spread to various other parts of the countryand generated pressure for a natural resource policy which is moresensitive to peoples needs and ecological requirements.Prominent Chipko figures include: Sunderlal Bahuguna, a Gandhian activistwho gave the Chipko slogan: ecology is permanent economy.Chandi Prasad Bhatt, fostered locally-based industries based on theconservation and sustainable use of forest wealth for local benefit.Dhoom Singh Negi, who, with Bachni Devi and many village women, first savedtrees by hugging them in the Chipko embrace. They coined the slogan:What do the forests bear? soil, water and pure air.
35. Who was the first lady cosmonaut?Valentina Tereshkova On the morning of 16 June 1963, Tereshkova took off in Vostok 6 launched faultlessly, and she became the first woman to fly into space.Tereshkova orbited the earth 48 times and spent almost three days in space. Tereshkova also maintained a flight log and took photographs of the horizon, which were later used to identify aerosol layers within the atmosphere. It took 19 years until the second woman, Svetlana Savitskaya, flew into space in Soyuz-T-7 in 1982. The first US lady astronaut to go into space was Sally K.Ride in 1983,who went in Challenger STS -7
36. Which is the largest living bird? Ostrich The Ostrich is a large flightless bird native to Africa (and formerly the Middle East). It is distinctive in its appearance, with a long neck and legs and the ability to run at speeds of about 65 km/h (40 mph). The Ostrich is the largest living species of bird and lays the largest egg of any bird species. The diet of the Ostrich mainly consists of seeds and other plant matter, though it eats insects. It lives in nomadic groups which contain between five and 50 birds. When threatened, the Ostrich will either hide itself by lying flat against the ground, or will run away. If cornered, it can cause injury and death with a kick from its powerful legs.
37. what are parasites?Parasites are living organisms that live at the expense of someother living beings. They depend completely for their nourishmentand sustenance on their host organism.IN plants the host range for most parasites isquite broad. However, a few are quitespecific to a small group of related species.After seed germination, the radicle contactsa host root, and a holdfast is formed on thesurface. A peglike root penetrates the hostsroot surface and grows into the water- andnutrient-conducting tissues, removing thematerials needed for development. Common animal (human) parasites: roundworm, protozoan, bacterium, "Bear corn" parasite on oak roots fungus, yeast
38. What is the main difference in the respiration of insects as against that of higher creatures?Respiration in insects is through a direct exchange of oxygen and carbondi oxide from the cells through pores in the skin and a system of tubularstructures called trachea. Unlike the higher organisms they do not havelungs and further do not need the help of Circulation for carrying oxygento different parts of their body. Air enters the insects body through valve-like openings in the exoskeleton. These openings (called spiracles) arelocated laterally along the thorax and abdomen of most insects -- usuallyone pair of spiracles per body segment. Air flow is regulated by smallmuscles that operate one or two flap-like valves within each spiracle
39. what is the main constituent of the human body? WATER Almost seventy percent of the Human body is made up of water. Mass of element Volume of Element in a 70-kg person purified element oxygen 43 kg 37 L carbon 16 kg 7.08 L hydrogen 7 kg 98.6 L nitrogen 1.8 kg 2.05 L calcium 1.0 kg 645 mL phosphorus 780 g 429 mL potassium 140 g 162 mL sulfur 140 g 67.6 mL sodium 100 g 103 mL chlorine 95 g 63 mL magnesium 19 g 10.9 mL iron 4.2 g 0.53 mL
40. What are chromosomes?Chromosomes are organized structures of DNA and proteins that are found incells. Chromosomes contain a single continuous piece of DNA, which containsmany genes, regulatory elements and other nucleotide sequences.Chromosomes also contain DNA-bound proteins, which serve to package theDNA and control its functions. The word chromosome comes from the Greekχρῶ μα (chroma, color) and σῶ μα (soma, body) due to their property of beingstained very strongly by some dyes. Representation of the 23 paired chromosomes of the human male A very long DNA molecule and associated proteins, that carry portions of the hereditary information of an organism. The DNA molecule is highly condensed. The human DNA helix occupy too much space in the cell. Small proteins are responsible for packing the DNA into units called nucleosomes. Chromosomes are stained with A-T (G bands) and G-C (R bands) base pair specific dyes. When they are stained, the mitotic chromosomes have a banded structure that unambiguously identifies each chromosome of a karyotype. Each band contains millions of DNA nucleotide pairs.
41.Can you give an example of a situation where Newton’s third law is applied?The simplest example is that of a jet engine. As thejet of burning gas is ejected from the rear, the planemoves forward due to the thrust provided by NTLAs the wings push the air downwards As the chap fires, the escapingThe air pushes the bird upwards. Bullet pushes the gun backwards In a recoil.
42. Why are gaps provided in between the joints of railway lines?Heat expands solids. Hence in summer months therailway lines,made of steel would expand.To avoid jamming of lines sufficient gaps areprovided.As all substances are made up of molecules, the spacebetween molecules determine the state of matter as beingsolid liquid or gas. The arrangement of molecules isdetermined by their internal enegy. As heat is a form ofenergy when a substance is heated Its internal energyincreases and thus the spacing between moleculesincrease leading to increase in volume that results in theexpansion of the body.
1. What is the difference between mass and weight of a body? Mass is the quantity of matter contained in a body whereas weight is the force acting on a body due to the acceleration due to gravityTo measure the mass of a body one should use acommon balance which has two pans hung from abeam so that the gravity acts on both the pansequally.On the other hand what one gets from a Springbalance is the weight of the body.Mass is expressed in units of ‘Kg’ while weight isexpressed in ‘Newtons’
44. What is the difference between fission energy and fusion energy? The binding energy released during the break up of radioactive heavy element, by Neutron bombardment is the Fission energy.The binding energy released when the light Elements (e.g. hydrogen)combines to formthe higher element (helium) iscalled the Fusion energy
45. What are the constituents of air?The major constituents of AIR are N+O+Ar+CO2 = 99.98% Nitrogen N2 78.084% Oxygen O2 20.947% Argon Ar 0.934% Carbon Dioxide CO2 0.033% 18.2 parts per Neon Ne million 5.2 parts per Helium He million per 1.1 parts Krypton Kr million per Sulfur dioxide SO2 1.0 parts million per Methane CH4 2.0 parts million
46. Give atleast three main differences between a plant cell and an animal cellPlant cell: cellwall-celulose a non living material, vacuole is larger in size, No organelles, and presence of green pigments called chloroplast. Animal cell: Vacuoles are smaller in number and size, no cell wall.
47.what is Oesophagus?The oesophagus orfood pipe is part of thedigestive system. It isalso sometimes calledthe gullet. It is the tubethat carries food fromyour mouth to yourstomach. It is about26cm (10.5 inches) longin adults. As it passesthrough the chest, on itsway to the stomach, itlies between thewindpipe (trachea) andspinal cord.
48. what is deceleration? Can you give an example when you find it useful?Deceleration is the opposite of acceleration.The rate of decrease of velocity with time is calleddeceleration.We use this while trying to bring a vehicle to stop.
49. Give examples of some foods which are rich in vitamins A, C and DFor vit A ; Spinach ,carrot, Butter, MangoFor vit C : all fresh citrus fruits like lemon, orangeFor vit D : Oil ,Milk , cod liver oil
50. What is the main function of red blood cells and where in human body the blood cells are produced?Main function of Red blood cells is to carry Oxygen toDifferent parts of the body. Blood cells are produced in theBone marrow Bone marrow is the soft tissue found in the hollow interior of bones. and It constitutes approximately 4% of total body weight There are two types of bone marrow: red marrow (consisting mainly of myeloid tissue) and yellow marrow (consisting mainly of fat cells). Red blood cells, platelets and most white blood cells arise in red marrow; some white blood cells develop in yellow marrow