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Ques 1: Choose the correct option:
(i) A ball rolling along the ground gradually slows down and finally comes to rest is an example of
(A) Muscular force
(B) Magnetic force
(C) Frictional force
(D) Electrostatic force
Ques 2: Choose the correct option:
(ii) Sound can travel through
(A) Solids only
(B) liquids only
(C) Gases only
(D) solids, liquids and gases.
Ques 3: Choose the correct option:
(iii) Which of the following is not a way to conserve water?
Ques 4: Choose the correct option:
(iv) The use of manure (which is not correct):
(A) Enhances the water holding capacity of the soil
(B) Improves soil texture
(C) Increases the number of friendly microbes
(D) Also becomes a source of water pollution
Ques 5: Choose the correct option:
(v) Which is the plant disease caused by micro-organism?
(B) Small pox
(C) Citrus Canker
Ques 6: Choose the correct option:
(vi) Rayon is obtained by
(A) Petroleum products
(B) Fully synthetic method
(C) Chemical treatment of wood pulp
(D) All methods
Ques 7: Choose the correct option:
(vii) Sodium metal is stored in
Ques 8: Choose the correct option:
(viii) The world's first oil well was drilled in:
Ques 9: Choose the correct option:
(ix) Which among the following is considered as the cleanest fuel?
(A) Cow dung cake
(D) Hydrogen gas
Ques 10: Choose the correct option:
(x) Which of the following is not a cell?
Ques 11: Give a suitable word for each of the following statements:
(i) Chemicals which control changes at adolescence stage.
Ans: (i) Hormones
Ques 12: Give a suitable word for each of the following statements:
(ii) Force exerted by a magnet on a piece of iron.
Ans: (ii) Magnetic force
Ques 13: Give a suitable word for each of the following statements:
(iii) The substance that reduces friction.
Ans: (iii) Lubricants
Ques 14: Give a suitable word for each of the following statements:
(iv) The characteristic of sound that determines loudness.
Ans: (iv) Amplitude
Ques 15: Give a suitable word for each of the following statements:
(v) Device used to check current.
Ans: (v) Tester
Ques 16: Give a suitable word for each of the following statements:
(vi) The Brightest star in the sky located close to Orion.
Ans: (vi) Sirius.
Ques 17: Who discovered the first antibiotic? Name any two antibiotics.
Ans: Alexander Fleming discovered first antibiotic penicillin. Two other common antibiotics are streptomycin and tetracycline.
Ques 18: Write any two properties of nylon.
Ans: (i) Nylon fibres are strong, elastic and light
(ii) They are easy to wash and lustrous.
Ques 19: What is carbonization?
Ans: As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonization.
Ques 20: When kerosene oil is heated a little, it will catch fire. But when wood is heated a little, it does not catch fire. Why?
Ans: If kerosene oil is heated a little, it catches fire. But if wood is heated a little, it does not catch fire because ignition temperature of kerosene oil is lower than that of wood.
Ques 21: What is desertification?
Ans: Removal of top layer of soil exposes the lower, hard and rocky layers. This soil has less humus and is less fertile. Gradually the fertile land gets converted into desert. It is called desertification.
Ques 22: Write difference between viviparous and oviparous animals.
Ans: Difference between viviparous and oviparous animals:
|Viviparous Animals||Oviparous Animals|
|The animals that give birth to young ones are called viviparous animals. e.g., Human beings, Cats, Dogs.||The animals that lay eggs are called oviparous animals. e.g., Frogs, fishes.|
Ques 23: Name the disease or side effects caused by deficiency of following hormones:
Ans: (a) Thyroxine is produced by thyroid gland. Its deficiency causes ?goiter? disease.
(b) A person suffers from diabetes, if pancreas does not produce the hormone insulin in sufficient quantities.
(c) Adrenal glands produce hormone adrenaline, which helps the body to adjust to stress, when a person is very angry, embarrassed or worried.
Ques 24: What does frictional force exerted on an object in a fluid depend on?
Ans: Frictional force on an object in a fluid depends on the speed with respect to the fluid and the nature of fluid. It also depends on the shape of the object, e.g., all vehicles are designed to have shapes that reduce fluid friction.
Ques 25: What happens when electricity is passed through ordinary water?
Ans: When the two terminals of battery are combined with negative and positive electrodes which are immersed in water, the water is dissociated into its components oxygen and hydrogen. Oxygen is collected on positive electrode and hydrogen is collected on negative electrode.
Ques 26: The oviducts of a woman are blocked. So doctor advised her for IVF.
(a) What is the full form of IVF?
(b) Why IVF is suggested to the woman? Justify.
(c) What do you call these babies born through this technique.
Ans: (a) The full form of IVF is in vitro fertilisation (fertilisation outside the body).
(b) IVF is suggested to the women because she is unable to bear babies because sperms cannot reach the egg for fertilisation. So, in this case doctors advised the woman for IVF. Where freshly released egg and sperms are kept together for few hours in vitro conditions in a test tube or any other apparatus.
(c) If in the case, fertilisation occurs, the zygote is allowed to develop for about a week and then it is placed in the mother?s uterus. Complete development takes place in the uterus and the baby is born like any other baby. This technique is called as test tube babies. This term is actually misleading because babies cannot grow in test tubes.
Ques 27: What are the advantages of manure?
Ans: Advantages of manure:
(i) It enhances the water holding capacity of the soil.
(ii) It makes the soil porous due to which exchange of gases becomes easy.
(iii) It increases the number of friendly microbes.
(iv) It improves the texture of the soil.
Ques 28: Explain the various shapes of bacteria.
Ans: The bacteria are classified into three types on the basis of their shape:
(a) Rod shaped (Bacillus):
(b) Round shaped (Coccus):
(c) Spiral shaped
Ques 29: What is rayon? Why is it called artificial silk? What are the uses of rayon?
Ans: Rayon is synthetic fibre having properties similar to those of silk. So, it is called artificial silk. It is obtained by chemical treatment of wood pulp. Rayon is a man-made fibre. It resembles silk, but it is cheaper than silk. It is mixed with cotton to make bed sheets, or mixed with wool to make carpets.
Ques 30: Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(i) How will she find the nature of the gas?
(ii) Write down word equations of all reactions taking place in this process.
Ans: (i) When charcoal is burnt, carbon dioxide gas is produced. This gas turns lime water milky. The nature of the gas can be tested by using moist red and blue litmus paper. No effect on red litmus but the gas turns blue litmus to red, so it is acidic in nature.
(ii) Equations of all the reactions are:
Carbon dixide + Lime water → Milky
Ques 31: What will happen if:
(i) we go on cutting trees?
(ii) the habitat of an animals is disturbed?
(iii) the top layer of soil is exposed?
Ans: (i) If we go on cutting trees, we will face the problem of food, wood, shelter etc. Also, the cutting of trees leads to the decrease in level of oxygen and also causes global warming.
(ii) If the habitat of an animal is disturbed, the animal will face extinction and survival becomes very difficult for it
(iii) The exposed layer has less humus and is less fertile. Gradually the fertile land gets converted into deserts. It is called deforestation.
Ques 32: Explain traditional ways of purifying water to make it fit for drinking.
Ans: The traditional ways of purifying water to make it fit for drinking are as follows:
(i) By filtering: This is a physical method of removing impurities. A popular household filter is a candle type filter.
(ii) By boiling: When water is heated, it boils at a temperature of 1000C. At this high temperature, all the harmful micro-organisms or germs present in water are killed and it becomes absolutely safe for drinking. Many households use boiling as a method for obtaining safe drinking water.
(iii) Chlorination: It is commonly used chemical method for purifying water. It is done by adding chlorine tablets or bleaching powder to the water.
Ques 33: Describe the 'Green House Effect' in your own words.
Ans: After the Sun's rays pass through the atmosphere, they warm the earth's surface. A part of the radiation that falls on the earth is absorbed by it and a part is reflected. The radiations which are trapped by the atmosphere are not allowed to go out of the earth's atmosphere.
These trapped radiations further warm the earth. As in a nursery, sun?s heat is allowed to get in but is not allowed to go out of the green house. The trapping of radiations by the earth's atmosphere performs a similar function. That is why it is called the greenhouse effect. Without this process, life would not have been possible on the earth because of the low temperatures. CO2 is one of the gases responsible for this effect.
Ques 34: Draw sketches to show the relative positions of prominent stars in (i) Ursa Major and (ii) Orion.
Ans: (i) Ursa Major: There are seven prominent stars in this constellation. They appear like a big ladle or a question mark. There are three stars in the handle of the ladle and four in its bowl.
(ii) Orion: Orion is another well-known constellation that can be seen during winter in the late evenings. It is one of the most magnificent constellations in the sky. It also has seven or eight bright stars. Orion is also called the hunter. The three middle stars represent the belt of the hunter. The four bright stars appear to be arranged in the form of a quadrilateral.
Ques 35: Write Do's and Don'ts during a thunderstorm.
Ans: Outside the house:
(i) Open vehicles, such as motor bikes, tractors, construction machinery and open cars are not safe.
(ii) Open fields, tall trees, shelters in park, elevated place do not protect us from lightning strokes.
(iii) Carrying an umbrella is also not safe.
(iv) Stay away from poles or other metal objects.
Inside the house:
(i) During a thunderstorm contact with telephone cords, electrical wires and metal pipes should be avoided.
(ii) Bathing should be avoided.
(iii) Electrical appliances like computers, TVs etc. should be unplugged. Electrical lights can remain on.