Water Vapor and Humidity

When an object is cool and warm air touches the cool object, the air cools and droplets of water forms on the outside of the object. This is the result of the hot and cold air coming into contact with each other. This water in the air is called water vapor. Water vapor is in the form of a gas.

Characteristics of water vapor include it being colorless, odorless, invisible, and has no taste. Humidity is the amount of water vapor in the air. When the in the air turns into a gas it is called evaporation.

Water vapor gets into the air day through the process of evaporation. Ocean water, and other bodies of water, is turned into water vapor using the energy from the sun. The molecules of the water is absorbed by the Sun's energy near the surface of the water which then evaporates into the air.

The changing of a gas into a liquid is called condensation. An example of condensation is the water which covers a mirror following a hot shower.

Another large source of water vapor in the air is when the plants absorb water through their roots and stems into their leaves. The leaves then give off water. The process of plants releasing water into the air is called transpiration.

All of the water in the air, whether it is from the world's ocean and other bodies of water, the water on a mirror following a hot shower, or the water a plant releases into the air; it is all called humidity because it is the amount of water vapor in the air.

When the air is filled with this water, the amount of water in the air can be measured. Another measurement used is called relative humidity. Relative humidity is a comparison between how much water is already in the air compared with how much water the air is able to hold at a certain temperature.

When the air can no longer hold the water vapor several things can happen. It may rain or snow depending on the temperature. The air could be become foggy or misty, or dew may appear on the grass in the mornings. Another problem with too much water vapor in the air, especially in the summer, is it becomes very uncomfortable and people began to sweat very easily.

In summary, the water in the air is called water vapor. Water vapor in the air forms when cold air and warm air come in contact with each other. Examples include moisture on the outside of a cold glass, or a mirror after a hot shower, which is also called condensation. When this water is turned into a gas and is released into the air it is called evaporation. Plants also release water into the air during a process called transpiration. Finally, all of the water vapor in the air is called humidity. A comparison between how much water is already in the air compared with how much water the air is able to hold at a certain temperature is called relative humidity. When this happens there could be rain, snow, fog, or dew.