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31 - 45: MCQs for General Science for Govt. Exams (UPSC and SSC)
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In this lesson, Dr. Roman Saini will discuss the MCQs related to various topics in General Science from Class 6 to Class 8 (Science) NCERT.

Roman Saini is teaching live on Unacademy Plus

Roman Saini
Part of a great founding team at Unacademy with Gaurav, Hemesh. Movies, Guitar, Books, Teaching.

U
Unacademy user
sir for minority any reservation is there
hi sir can u provide this into PDF format how can I dowload
Q38 I think rusting is also a physical change because it changes the size of iron .. Please correct me if I am wrong :)
Rusting is a chemical reaction. Iron oxidizes in the presence of moisture to form iron oxide (rust).
Aashay Jain
3 years ago
yes but it changes(reduces) the size also ,,that means it should be considered as physical change..
The size change is kinda the result of the chemical change. The consequence of rusting.
Abhimanyu singh
a year ago
ya but the question here is about the physical change whether it happens through chemical reaction
Thank u so much sir for this lesson. This has made learning general science so easy for me! you are great sir.
Thanks alot Roman sir,Awesome series especially for checking out one's MCQ solving ability in a shorter span of time.Sir,is it downloadable?
9/10 Thank you sir
Sudharsan Rajan
3 years ago
9/15* Thank you sir
  1. Q31. Phenolphthalein, a commonly used chemical in laboratories is a/an a. Strong Acidic solution b. Strong basic solution c. Neutral solution d. Indicator


  2. Answer:d Explanation: Acids are sour in taste. Bases, are bitter in taste and soapy to touch. Acidturns blue litmus red. Bases turn redlitmus blue Substances which are neither acidic nor basic are called neutral. Solutions of substances that show different colour in acidic, basic and neutral solutions are called indicators. Phenolphthalein is a commonly used indicator in laboratories.


  3. Q32. Quick lime is applied to soils which are highly a. Acidic b. Basic c. Porous d Infertile


  4. Answer: a Explanation: Excessive use of chemical fertilisers makes the soil acidic. Plants do not grow well when the soil is either too acidic or too basic. When the soil is too acidic, it is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide). If the soil is basic, organic matter is added to it. Organic matter releases acids which neutralises the basic nature of the soil


  5. 033. Calamine solution is applied over an ant bite because. a. t makes the skin soft and relieves the pain. b. It n b. t neutralizes the effect of ant bite which injects acid into c. t neutralizes the effect of ant bite which injects base into d. the skin. the skin. It is a painkiller.


  6. Answer: b Explanation: When an ant bites, it injects the acidic liquid (formic acid) into the skin. The effect of the acid can be neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains zinc carbonate.


  7. Q34. Which of the following chemicals is also known as blue vitriol (neela thotha)? a. Copper sulphate b. Magnesium sulphate b. Magnesium sulph c. Ferrous sulphate d. Magnesium hydroxide


  8. Answer: a Explanation: Green vitriol- Hydrated ferrous sulphate Blue vitriol Epsom salts- Magnesium sulphate hepta-hydrate Milk of magnesia- Magnesium hydroxide Copper sulphate


  9. Q35. Which of the following is the standard test for carbon dioxide? a. Reaction of carbon dioxide with water b.Reaction of carbon dioxide with lime water c. Reaction of carbon dioxide with copper sulphate d. Reaction of carbon dioxide with chlorophyll


  10. Answer: b Explanation: When carbon dioxide is passed through lime water, calcium carbonate is formed, which makes lime water milky. The turning of lime water into milky is a standard test of carbon dioxide


  11. 036. Which of the following is essential for rusting of iron? 1. Oxygen 2. Carbon dioxide 3.Moisture 4. Heat Choose the correct code. a. 1 and 2 only b.2 and 3 only c. 1 and 3 only d. and 4 only


  12. Answer: c Explanation: For rusting, the presence of both oxygen and water (or water vapour) is essential. In fact, if the content of moisture in air is high, which means if it is more humid, rusting becomes faster.


  13. Answer: d Explanation: In order to prevent rusting, prevent iron articles from coming in contact with oxygen, or water, or both. One simple way is to apply a coat of paint or grease. In fact, these coats should be applied regularly to prevent rusting. Another way is to deposit a layer of a metal like chromium or zinc on iron. This process of depositing a layer of zinc on iron is called galvanisation. The iron pipes we use in our homes to carry water are galvanised to prevent rusting. Another way to prevent rusting of iron is by mixing iron with carbon and metals like chromium, nickel and manganese to make stainless steel which does not rust


  14. Q39. The day to day conditions of the atmosphere with respect to rainfall, temperature, wind velocity etc. is called as a. Weather Climate c. Ecology d. Meteorology


  15. Answer: c Explanation: Self-explanatory


  16. Q41. Energy in a cyclone is derived from Sun b. vaporation C. Condensation d. Precipitation


  17. Answer: c Explanation: Water takes up heat from the atmosphere to change into vapour. These water vapours then form the clouds. When water vapour changes back to liquid form as raindrops (condensation), this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low-pressure system with very high-speed winds revolving around it. t is this weather condition that we call a cyclone


  18. Q43. Humus is present in a. A horizon of the soi b. B horizon of the soil c. Chorizon of the soil. d. H horizon of the soi


  19. Q44. If the amount of large and fine particles is about the same, then the soil is called a. Clayey soil b. Loamy soil c. Sandy soil d ertile soil


  20. Q45. Percolation of water is highest in a. Clayey soil b Loamy soil c. Sandy soil d Fertile soil


  21. Answer: c Explanation: Percolation rate of water is different in different types of soil. It is highest in the sandy soil and least in the clayey soil.