Properties of Air

Why do morning fogs go away by lunchtime?

The sun heats up the Earth. This spreads out the air molecules, leaving more room for water vapor. At the same time, the sun's heat is pushing the fog droplets to evaporate. Once there is enough room in the air for the water molecules, they evaporate & become water vapor.

What happens to the temperature of the air as altitude increases?

The temperature decreases

Why does relative humidity vary greatly over the course of a day, while the humidity does not change very much.

Relative humidity is affected greatly by temperature. As the temperature rises over the day due to the sunlight heating the Earth, the relative humidity goes down. As the Earth cools when the sun goes down, the air molecules get closer together, lessening the amount of space for water vapor, so the relative humidity goes up. Humidity is just the amount of water in the air, which typically does not change much in a day.

How is the air above a fire different than the air next the the fire?

The air above a fire is hotter. Therefore, it is less dense, rising, & creating an area of low air pressure right above the fire. The air next to the fire is cooler in comparison, so it is more dense & higher pressure.

What factors affect relative humidity?

The amount of water vapor in the air (humidity). The greater the amount of water vapor in the air, the greater the relative humidity. The temperature of the air. Hotter air holds more water vapor than cold air.

If you put an inflated balloon in a freezer, what will happen to its volume & mass. Explain.

The balloon is inflated with dry air. The volume will decrease as the molecules get closer to one another. The mass will stay the same, as number of the molecules will not change.

How does air move to create an area of high pressure?

Air cools down, gains density, & falls to the ground. This pushes air into the ground, adding pressure.

How does air move to create an area of low pressure?

Air warms up, loses density, & rises up. This pulls air away, lessening the pressure on the ground.

What happens to density, pressure, & particle movement (temperature) when air is cooled?

As air is cooled, density increases (volume decreases/ particles move closer together) In the atmosphere, the cold air sinks due to its increased density, pressing harder on the ground below it. This makes the air pressure higher in cold conditions. Temperature decreases because particles slow down.

What happens to density, pressure, & particle movement (temperature) when air is warmed?

As air is warmed, density decreases (volume increases/ particles spread out). In the atmosphere, the warm air rises due to its lowered density, lowering the air pressure underneath it. Temperature increases because particles speed up.

Compare & contrast relative humidity & humidity.

Humidity is the amount of water vapor in the air. Relative humidity is the percent the air is "filled up" with water vapor.

How are particles (molecules/atoms) arranged in a dense substance vs. a less dense substance.

In high density substances, particles are closer together than in low density substances.

What conditions can cause air to rise?

Warm conditions lower the density of air, so it will begin to "float" on the cooler, more dense, surrounding air.

Explain relative humidity and the formation of clouds.

When relative humidity reaches 100%, condensation occurs. This is how clouds form. This can happen either because the air becomes colder, or because more water vapor is added to the air.