Vapour | Jamb(UTME)

Unsaturated and Saturated Vapours

1. Vapours are the gaseous form of a liquid or solid substance at a temperature below its boiling point.
2. Unsaturated vapour contains less vaporized substance than it can hold at a given temperature.
3. If more liquid evaporates, unsaturated vapour becomes saturated.
4. Saturated vapour occurs when a vapour contains the maximum amount of substance it can hold at a specific temperature.
5. In a closed container, equilibrium is reached between evaporation and condensation, creating saturated vapour.
6. Increasing temperature increases the capacity of air to hold vapour, making it unsaturated again.
7. Unsaturated vapours can absorb more vapour, while saturated vapours cannot without condensing.
8. The state of a vapour (unsaturated or saturated) depends on temperature and pressure.
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Relationship Between Saturated Vapour Pressure (S.V.P.) and Boiling

9. Saturated vapour pressure (S.V.P.) is the pressure exerted by saturated vapour at a specific temperature.
10. As temperature increases, S.V.P. also increases because more liquid evaporates.
11. Boiling occurs when the S.V.P. equals the atmospheric pressure.
12. At higher altitudes, where atmospheric pressure is lower, boiling occurs at a lower temperature.
13. In a pressure cooker, higher pressure raises the boiling point, cooking food faster.
14. S.V.P. explains why water boils at $100^\circC$ at sea level but at lower temperatures on mountains.
15. Substances with higher S.V.P. evaporate more quickly, like alcohol compared to water.
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Formation of Dew, Mist, Fog, Clouds, and Rain

16. Dew forms when air cools and reaches the dew point, causing water vapour to condense on surfaces.
17. Dew is common on clear, cool nights when the ground loses heat rapidly.
18. Mist forms when tiny water droplets suspend in the air, reducing visibility slightly.
19. Fog is a denser form of mist, significantly reducing visibility and often forming in humid, cool conditions.
20. Clouds form when warm air rises, cools, and condenses into water droplets or ice crystals around tiny particles.
21. Clouds are classified by their shape and altitude, such as cumulus (fluffy), stratus (layered), and cirrus (wispy).
22. Rain occurs when water droplets in clouds combine and grow heavy enough to fall to the ground.
23. Rain formation depends on the size and weight of droplets overcoming air resistance.
24. Precipitation can also occur as snow, sleet, or hail depending on atmospheric temperature and conditions.
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Study of Dew Point, Humidity, and Relative Humidity

25. The dew point is the temperature at which air becomes saturated and condensation begins.
26. High dew points indicate moist air, while low dew points indicate dry air.
27. Humidity is the amount of water vapour in the air.
28. Absolute humidity is the actual mass of water vapour per unit volume of air.
29. Relative humidity is the ratio of the current amount of water vapour in the air to the maximum it can hold at a specific temperature.
30. The formula for relative humidity is:
    
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    $Relative Humidity ($
31. High relative humidity makes the air feel muggy and slows evaporation, while low humidity feels dry.
32. Relative humidity depends on temperature—warmer air can hold more moisture, reducing relative humidity.
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Hygrometry

33. Hygrometry is the study and measurement of atmospheric humidity.
34. Instruments used to measure humidity are called hygrometers.
35. Simple hygrometers use materials like hair that change length based on humidity.
36. Digital hygrometers use electronic sensors for precise humidity measurements.
37. Hygrometry helps monitor weather, predict rain, and ensure comfort in indoor environments.
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Estimation of Atmospheric Humidity Using Wet and Dry Bulb Hygrometers

38. A wet and dry bulb hygrometer consists of two thermometers: a wet bulb and a dry bulb.
39. The dry bulb thermometer measures the ambient air temperature.
40. The wet bulb thermometer has its bulb covered with a damp cloth, and it measures a lower temperature due to evaporation.
41. The wet bulb temperature is lower when the air is dry because evaporation cools the thermometer more.
42. The difference between wet and dry bulb temperatures is called the wet bulb depression.
43. A larger depression indicates lower humidity, while a smaller depression indicates higher humidity.
44. Using a psychrometric chart or formula, the relative humidity can be calculated from the two temperatures.
45. The formula for calculating relative humidity from wet and dry bulb temperatures involves tables or equations linking temperature and pressure.
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pplications of Humidity Measurements

46. Monitoring humidity is crucial in weather forecasting to predict rain, fog, or heatwaves.
47. Relative humidity affects human comfort—high humidity feels hotter because sweat evaporates slower.
48. Indoor humidity control prevents mold growth and protects materials like wood or paper.
49. Hygrometry is essential in industries like agriculture, aviation, and food storage.
50. Air conditioning systems regulate indoor humidity for comfort and health.
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Practical Observations

51. On a hot day, a high relative humidity makes you feel warmer because sweat doesn't evaporate quickly.
52. Fog forms in valleys in the morning because cool air traps moisture near the ground.
53. Dew forms on grass because the ground cools faster than the surrounding air.
54. High humidity makes it harder for clothes to dry due to reduced evaporation rates.
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Interesting Facts

55. Clouds float because the tiny droplets or ice crystals they are made of are spread out and supported by rising air currents.
56. The Sahara Desert has one of the lowest relative humidities on Earth.
57. A 100% relative humidity means the air is fully saturated, and any additional cooling will result in condensation.
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Importance of Humidity in the Atmosphere

58. Humidity regulates global temperatures by storing and releasing heat during condensation and evaporation.
59. Humidity affects how far sound travels—higher humidity allows sound to travel farther.
60. Studying humidity is crucial for managing water resources, agriculture, and human health.
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