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Class 9 - Physics

Sound

3. Humidity of Air


The amount of water vapours present in air is represented by a term called humidity. When the amount of water vapours present in the air is small, the air appears to be 'dry' and we say that the humidity is low.On the other hand, when the amount of water vapours in the air is large, the air appears to be 'damp' and we say that the humidity is high. So, humidity of air tells us the degree of 'dampness' of air.
When the humidity of air is low, then the rate of evaporation is high, and water evaporates more readily. Under these conditions, sweat from our body evaporates readily and we feel cool and comfortable.The wet clothes dry quickly under the conditions of low humidity of air. When the humidity of air is high, then the rate of evaporation is low, and water evaporates very slowly. In the later part of summer,the humidity of air increases. People sweat a lot in such weather. But the sweat from our bodies does not evaporate readily due to high humidity of air. Such weather becomes muggy (damp) and we feel hot and uncomfortable. This type of weather is experienced during cloudy days in the rainy season and in areas close to the sea (coastal areas). The wet clothes take a long time to dry when the humidity of air is high.

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Notes


Sound - Notes
1. Sound - Study Points
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2. Effect of 'Heating' and 'Cooling' on a Saturated Solution
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3. 1. Solid to Liquid Change : Melting
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4. 3. Gas to Liquid Change : Condensation
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5. 1. Latent Heat of Fusion (Solid to Liquid Change)
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6. 4. Wind Speed
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7. 2. Liquid to Gas Change : Boiling (or Vaporisation)
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8. 4. Liquid to Solid Change : Freezing
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9. Latent heat
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10. Effect of Change pressure
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11. 1. Temperature
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12. Effect of Change of Temperture
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13. Two More States of Matter : Plasma and Bose-Einstein Condensate
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14. 4. The Particles of Matter Attract Each Other
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15. Evaporation
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16. 2. Surface Area of the Liquid
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17. 2. The Particles of Matter have Spaces Between Them
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18. 2. Latent Heat of Vaporisation (Liquid to Gas Change)
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19. 3. Humidity of Air
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20. Why Solids, Liquids and Gases Have Different Properties
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21. Classification Of Matter As Solids, Liquids And Gases
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22. Diffusion in Liquids
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23. Properties of Solids
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24. Properties of Liquids
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25. 1. The Particles of Matter are Very, Very Small
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26. 3. The Particles of Matter are Constantly Moving
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27. Liquids
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28. Dissolving a Solid in a Liquid
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29. Change of State of matter
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30. Matter is made of particles
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31. Gases
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32. Rigid and Fluid
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33. Factors Affecting Evaporation
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34. Diffusion
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35. To Show That Solids and Liquids Cannot be Compressed but Gases Can be Compressed Easily
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36. Characteristics of Particles of Matter
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37. Solids
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38. Cooling Caused by Evaporation
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39. The Common Unit Of Temperature and Si Unit Of Temperatre
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40. Mixing of Two Gases
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41. Sublimation
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42. Matter In Our Surroundings
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43. Evidence for Particles in Matter
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44. Movement of Pollen Grains in Water
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45. To Show that Liquids do not have a Fixed Shape but they have a Fixed Volume
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46. Gases Can be Liquefied by Applying Pressure and Lowering Temperature
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47. Diffusion in Solids
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48. To Show the Presence of Water Vapour in Air
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49. To Show that Gases do not have a Fixed Shape or a Fixed Volume
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50. Diffusion in Gases
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