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Scientific concepts and phenomena

• Saturated water-vapor content The maximum mass of water vapor air can hold at a given temperature (read from the saturation curve). Units: g/m³.

• Actual water-vapor content The current mass of water vapor present in the air (g/m³).

• Relative humidity (RH) The ratio of actual water-vapor content to the saturated water-vapor content at that temperature, usually expressed as a percentage.

• Dew point The temperature to which air must be cooled (at constant water-vapor content) to reach saturation; below that temperature condensation (dew) begins.

• Condensed (condensation) amount The mass of water that condenses when air is cooled from its current temperature to a lower temperature — the difference between the current actual vapor and the saturation vapor at the lower temperature.

How to read values from a saturation‑vapor graph

1. To get saturated water‑vapor content at a given temperature

   • Move vertically from the given temperature until you hit the saturated‑vapor curve; read the corresponding vapor amount (g/m³) on the vapor axis.

2. To get actual water‑vapor content

   • From the air’s current state point, read the vapor amount on the vertical (vapor) axis (g/m³).

3. To compute relative humidity

   • Use: RH = (actual water‑vapor content / saturated water‑vapor content at that temperature) × 100%

4. To find the dew point

   • From the current actual vapor content, move left (decrease temperature) until you intersect the saturated‑vapor curve; the temperature at that intersection is the dew point.

5. To find the amount of condensation when cooling to a new (lower) temperature

   • Condensed amount = current actual water‑vapor content − saturated water‑vapor content at the target (lower) temperature

Worked example (air A)

• Saturated vapor at current temperature ≈ 27.2 g/m³ (video also states 27.1 g/m³).
• Actual water‑vapor content = 14.7 g/m³.
• Relative humidity ≈ 14.7 / 27.2 ≈ 0.540 → ≈ 54%.
• Dew point (for air A) = 20 °C (temperature at which 14.7 g/m³ intersects the saturation curve).
• If cooled to 0 °C, saturated vapor at 0 °C ≈ 3.8 g/m³ → condensed amount = 14.7 − 3.8 = 10.9 g (of water per unit air volume, as used in the graph).

Researchers / sources

• None listed in the subtitles.