Brain Grain · braingrain.in
Science — Practice Paper · Set 1
Part I — Multiple Choice Questions 10 × 1 = 10
Choose the correct answer. (Answer all questions.)
1.A tadpole develops into an adult frog by the process ofi. fertilisationii. metamorphosisiii. embeddingiv. budding[1]
2.The number of nuclei present in a zygote isi. noneii. oneiii. twoiv. four[1]
3.Friction on toy car in increasing order on wet marble, dry marble, newspaper and towel isa. wet marble floor, dry marble floor, newspaper and towelb. newspaper, towel, dry marble floor, wet marble floorc. towel, newspaper, dry marble floor, wet marble floord. wet marble floor, dry marble floor, towel, newspaper[1]
4.The right meal for adolescents consists ofi. chips, noodles, cokeii. chapati, dal, vegetablesiii. rice, noodles and burgeriv. vegetable cutlets, chips and lemon drink[1]
5.Image formed by a plane mirror isa. virtual, behind mirror and enlargedb. virtual, behind mirror and same sizec. real at surface and enlargedd. real, behind mirror and same size[1]
6.When a glass rod is rubbed with silk cloth, the roda. and cloth both acquire positive chargeb. becomes positively charged while cloth becomes negatively chargedc. and cloth both acquire negative charged. becomes negatively charged while cloth becomes positively charged[1]
7.Reproductive age in women starts when theiri. menstruation startsii. breasts start developingiii. body weight increasesiv. height increases[1]
8.Tester bulb glows brightly for liquid A and dimly for liquid B. What follows?i. liquid A is a better conductor than liquid Bii. liquid B is a better conductor than liquid Aiii. both are equally conductingiv. conducting properties cannot be compared[1]
9.The process of conversion of sugar into alcohol is calledi. nitrogen fixationii. mouldingiii. fermentationiv. infection[1]
10.Arrange rolling, static and sliding frictions in decreasing order.a. rolling, static, slidingb. rolling, sliding, staticc. static, sliding, rollingd. sliding, static, rolling[1]
Part II — Short Answer Questions 12 × 2 = 24
Answer briefly. (Answer all questions.)
11.Fill in blanks about plane mirror distance, touching ear in mirror, pupil in dim light and night birds.[2]
12.Write 10 lines on the usefulness of microorganisms in our lives.[2]
13.For copper purification, which electrode should impure copper be connected to and why?[2]
14.Why did the teacher advise Gurmit not to use a laser torch?[2]
15.Write True or False: fossil fuels can be made in laboratory; CNG is more polluting than petrol; coke is almost pure carbon; coal tar is a mixture; kerosene is not a fossil fuel.[2]
16.A mosquito vibrates wings at 500 vibrations per second. What is the time period?[2]
17.Explain the process of formation of petroleum.[2]
18.Give two differences between a zygote and a foetus.[2]
19.Explain why fossil fuels are exhaustible natural resources.[2]
20.Trees are being continually cut to meet demands in factories and for shelter. Is it justified? Discuss.[2]
21.Does pure water conduct electricity? If not, how can it be made conducting?[2]
22.Explain how soil gets affected by continuous plantation of crops in a field.[2]
🔑 Show Answer Key — Set 1
- 1. (ii) metamorphosis.
- 2. (ii) one.
- 3. (a) wet marble floor, dry marble floor, newspaper and towel.
- 4. (ii) chapati, dal, vegetables.
- 5. (b) virtual, behind the mirror and of the same size as the object.
- 6. (b) becomes positively charged while the cloth becomes negatively charged.
- 7. (i) menstruation starts.
- 8. (i) liquid A is a better conductor than liquid B.
- 9. (iii) fermentation.
- 10. (c) static, sliding, rolling.
- 11. (a) 2 m (b) left, left hand (c) large (d) fewer cones than rods.
- 12. Microorganisms help set curd, make bread, prepare alcohol and vinegar, and produce antibiotics and vaccines. They decompose dead plants and animals, recycle nutrients, clean organic waste and improve soil fertility. Rhizobium and blue-green algae fix nitrogen. Some microbes are also used in large-scale production of medicines, enzymes and fermented foods.
- 13. The impure copper rod should be connected to the positive terminal. Copper dissolves from it into solution and deposits on the thin pure copper plate connected to the negative terminal.
- 14. Laser light is very intense and can damage the retina if it enters the eye.
- 15. (a) False (b) False (c) True (d) True (e) False.
- 16. $0.002$ s.
- 17. Petroleum formed from dead sea organisms buried under sand and clay. Over millions of years, absence of air, high pressure and high temperature converted the remains into petroleum and natural gas.
- 18. A zygote is the single cell formed by fusion of gametes; a foetus is a later stage with recognisable body parts. The zygote begins division, while the foetus grows in the uterus before birth.
- 19. They are present in limited quantities and take millions of years to form. Human use is much faster than their formation, so they can be exhausted.
- 20. Cutting trees may be needed for essential development, but uncontrolled cutting is not justified because it harms biodiversity, climate, soil and water. Development should use minimum forest land, reforestation, recycling, protected areas and sustainable planning.
- 21. Pure water is a poor conductor. Adding a small amount of salt, acid or base makes it conducting.
- 22. Continuous cropping removes the same nutrients repeatedly from soil. Without manure, fertilisers or crop rotation, the soil becomes nutrient deficient and less fertile.