## Saturday, 23 July 2011

### CBSE Class IX (9th) Science | Chapter 1. MATTER IN OUR SURROUNDINGS | Lesson Exercises

Question 1. Convert the following temperatures to the celsius scale.
(a) 293 K (b) 470 K.

Answer : As we know 0° C =273.16 K. For convenience, we take 0° C = 273 K after rounding off the decimal.
To change a temperature on the Kelvin scale to the Celsius scale we have to subtract 273 from the given temperature

(a) 293 K =  293-273  = 20° C
(b) 470 K = 470-273   = 197° C

Question2. Convert the following temperatures to the Kelvin scale.
(a) 25°C (b) 373°C.

Answer : Kelvin is the SI unit of temperature, 0° C =273.16 K. For convenience, we take 0° C = 273 K
after rounding off the decimal. To  convert a temperature on the Celsius scale to the Kelvin scale we have to add 273 to the given temperature.

(a) 25°C = 25 + 273 = 298 K

(b) 373°C = 373 + 273 = 646 K

Question3. Give reason for the following observations.
(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.

Answer : (a) Naphthalene balls disappear with time without leaving any solid. This is due to the property of sublimation. Some solids do not exist in their liquid form or changes from solid to liquid; instead they directly evaporate from their solid form to vapour forms. Naphthalene is a sublime substance with very high vapors pressure,  that show the property of sublimation. So naphthalene balls disappear after some time due to the property of sublimation.

(b) We can get the smell of perfume sitting several metres away. This is due to high rate of  diffusion of perfume particles. Liquid generally vaporize at normal temperature. Perfume particles on vaporizing, intermix on their own with each other and air molecules around at a very fast rate. They do so by getting into the spaces between the particles. This intermixing of particles of two different types of matter on their own is called diffusion.Therefor the smell of perfume reach us sitting metres away.

Question4. Arrange the following substances in increasing order of forces of attraction between the particles. water, sugar, oxygen.

Answer : Substances in increasing order of forces of attraction between the particles.
• Oxygen
• Water
• Sugar

Question5. What is the physical state of water at.
(a) 25°C (b) 0°C (c) 100°C ?

Answer : Physical states of water at given temperatures :
(a) 25°C - Liquid as familiar water
(b) 0°C  - Solid  as ice
(c) 100°C- Gaseous as water vaporour
Question6. Give two reasons to justify.
(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.

Answer :  (a) water at room temperature is a liquid because its melting temperature is with in range of room temperature. As we know force of molecular attraction of a substance becomes high at low temperature and weak  at high temperature. Due to this  water at 0°C becomes solid due to increased molecular particles attraction.At room temperature arround 20 °C, due to increase in tempreture,  kinetic energy of the water particles increases. Due to the increase in kinetic energy, the particles start vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the water particles. The
particles leave their fixed positions and start moving more freely. A stage is reached when the solid ice melts and is converted to water a liquid.

(b) an iron almirah is a solid at room temperature.This is because the melting point of iron is  1536 °C or 2797 °F or 1809 K where as room temperature is around 20°C. At this temperature, kinetic energy of the iron molecules is not enough to  overcomes the forces of attraction between the water particles. There for iron almirah is solid at room temperature.

Question7. Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer : The heat energy  absorbed by ice to change to liquid state, without showing any rise in temperature is known as the latent heat. We already know, the  heat can change the physical state of a matter by overcoming the forces of attraction between the particles. For water freezing point and melting point is 0°C. So water has extra amount of hidden energy as compare to ice.

Question8. What produces more severe burns, boiling water or steam?
Answer : Steam produces more severe burns as compare to boiling water as it has extra high heat energy.

Question9. Name A,B,C,D,E and F in the following diagram showing change in its state

Answer :

#### 84 comments:

1. thank you very much sir, you are helping to thousands of people. keep doing this noble practice.

1. Yesvright

2. Thanks a lot sir for this

3. Thanks a lot sir for this

4. Thanks a lot sir for saving from tution teacher

5. Thankyou so much sir

6. Thanks sir

7. Thanks lot sir

8. Thank you bhai Saab .....

2. thank you very much sir jee

3. Thank you Sir
You live long for doing this

4. Thank u sir while using this my life is amazing.... This help me lot....

5. Thanks sir

6. Thank u sir so lot

7. Thank you ....it is very helpful to us ..

8. Thanks u very much sir for this respective answer

9. Thank you so much jagdish sigh��

10. Thanks you sir ji

11. Thanks sir

12. Thank u sir

13. Thanks u soo much sir this help me a lot

14. Thank u so much sir😄😄

15. Thanks dear sir

16. Thanks dear sir

17. Thanks sir

18. Thanks so much sir

19. Thanks a lot

20. Thank you sir

21. Thank you so much sir!! 😊

22. Que. 4 ka ans. Shi hai.

23. Que 4 ka ans shi hai.

24. OK ALLRIGHT THNX TO ALL FOR HELPING

25. Thank you very much for more information 😀😁😊

26. Thank you sir

27. U r doing a good work

28. Thankyou sir

29. Thank you sir 🙏 for help me
How r u i am don't know but u r job is good always do that sir 🙏👍👍🏻👍👍👍

30. Sir I have problem but after searching this I am agree with yours thank you sir

31. SIR CONTACT ME I AM A FOUNDER OF DARBHANGA PUBLIC SCHOOL

32. Sir mujhe science bahut bekar lgti h isliye me cpy Karke lights hoon

33. Thanks alot

34. Thank you sir for helping me

35. Thanks you sir
It become easy to study for hundred of the students in all over the country

36. Thanks sir for this it will help thousands of students👩‍🎓

37. Thank uh so much sir

38. thanks of lot

39. Thank you sir ur answers are very reasonable and easily understood thank you sir

40. It helps to study

41. Thank You 😊 very much teacher.

42. Thank you sir for helping me

43. thanku sir

44. Thank you sir

45. Very good answer sir

46. Thank you sir for helping 😊😊😊😊

47. Thanks for helping me

48. its helping me a lot for all my cw,exam and etc

49. thxx u sir

50. Thnq uu vry much sir😌for your help.. Your answers helped me to score good marks in my exam 😇

51. Thanks 😊 sir apki vajh se mujhe science samajh me aayi he

52. Thank you sir /miss for helping me with the question answered

53. Thank you so much sir

54. Tqu so much

55. T Q U S O M U C H

56. thank you very much sir, you are helping to thousands of people. keep doing this noble practice.

57. Thanks🙏 Sir for this answer🥰

58. Tq so much teachers

59. Thank u riiii 🙏

60. Thnaks for provide this answers
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "url": "https://www.cbsemaster.org/2011/07/cbse-class-ix-9th-science-chapter-1.html?showComment=1587642342732", "fetch_time": 1669844526000000000, "content_mime_type": "text/html", "warc_filename": "crawl-data/CC-MAIN-2022-49/segments/1669446710771.39/warc/CC-MAIN-20221130192708-20221130222708-00848.warc.gz", "warc_record_offset": 721054062, "warc_record_length": 28412, "token_count": 1871, "char_count": 7178, "score": 4.1875, "int_score": 4, "crawl": "CC-MAIN-2022-49", "snapshot_type": "latest", "language": "en", "language_score": 0.8937101364135742, "file_path": "/sailhome/yjruan/project/latent-lm/data/processed/finemath-4plus/finemath-4plus/train-00016-of-00064.parquet"}