A cloud formation in a jar model shows how real clouds form in the atmosphere using simple classroom materials. Warm water adds water vapor to the air inside the jar, ice cools the air near the top, and smoke provides tiny particles for droplets to form on. This project matters because it connects weather, temperature, phase changes, and the water cycle in one visible demonstration.
It also helps students see that clouds are made of tiny liquid water droplets or ice crystals, not water vapor itself.
In the model, warm water evaporates and increases the humidity inside the jar. When the moist air rises and cools near the ice-covered lid, some water vapor condenses into tiny droplets. Smoke particles act like condensation nuclei, giving the water molecules surfaces to collect on.
The same process happens in nature when moist air rises, cools to its dew point, and forms cloud droplets around dust, sea salt, pollen, or other tiny particles.
Key Facts
- Clouds form when moist air cools to its dew point and water vapor condenses into tiny droplets or ice crystals.
- Evaporation changes liquid water into water vapor: liquid water + heat energy -> water vapor.
- Condensation changes water vapor into liquid water: water vapor -> liquid droplets.
- Relative humidity = actual water vapor in air / maximum water vapor the air can hold x 100%.
- Warm air can hold more water vapor than cold air, so cooling moist air can cause condensation.
- The 10 main cloud types are cirrus, cirrostratus, cirrocumulus, altostratus, altocumulus, stratus, stratocumulus, nimbostratus, cumulus, and cumulonimbus.
Vocabulary
- Evaporation
- Evaporation is the process in which liquid water gains energy and changes into water vapor.
- Condensation
- Condensation is the process in which water vapor cools and changes into liquid water droplets.
- Dew point
- The dew point is the temperature at which air becomes saturated and water vapor begins to condense.
- Condensation nucleus
- A condensation nucleus is a tiny particle, such as smoke, dust, or salt, that water droplets can form around.
- Relative humidity
- Relative humidity is the percentage of water vapor in the air compared with the maximum amount the air can hold at that temperature.
Common Mistakes to Avoid
- Thinking the cloud is made of water vapor is wrong because water vapor is an invisible gas, while the visible cloud is made of tiny liquid droplets or ice crystals.
- Leaving out smoke or particles makes the cloud harder to see because water droplets need condensation nuclei to form efficiently.
- Using cold water instead of warm water reduces evaporation, so there may not be enough water vapor in the jar to make a strong cloud.
- Removing the ice too soon weakens the demonstration because the moist air needs cooling near the top of the jar to reach condensation conditions.
Practice Questions
- 1 A jar contains air at 24°C, and the air near the ice lid cools to 12°C. If the dew point is 14°C, should condensation occur near the lid? Explain using the temperatures.
- 2 A student adds 200 mL of warm water to a jar. After the demonstration, 15 mL has evaporated or been removed as vapor and droplets. What percent of the original water amount is this?
- 3 In the cloud in a jar model, why do smoke particles make the cloud appear faster and thicker than using only warm water and ice?