Making a cloud in a bottle is an easy and fun science project that demonstrates how tiny liquid droplets form from a gas or vapor. There is more than one way of making a cloud in a bottle. Here are three simple methods you can try.
How Real Clouds Form
First, here’s a quick review of how real clouds form in the atmosphere:
Clouds form in the lower layers of the Earth’s atmosphere, which are the troposphere, stratosphere, and mesosphere. Three factors that affect their formation are temperature, pressure, and condensation nuclei. The temperature of air affects its density and causes a column of air to rise or sink. Cold air is more dense (heavier) than warm air. Warmer air holds more water than colder air.
So, when warm air containing a lot of water vapor rises, it experiences adiabatic cooling. In other words, cooling occurs due to changes in pressure. Cool air holds less water, but the tiny water droplets that make clouds don’t spontaneously appear. Instead, they coalesce around particles, like pollen and dust. These particles are called condensation nuclei.
How to Make a Cloud in a Bottle With Water and a Match
Probably the easiest way to make a cloud in a bottle is using a plastic bottle, water, and a match. This method produces a water vapor cloud, just like a real cloud.
- 1-liter plastic bottle
- Warm water
- Pour enough warm water into the bottle to cover the bottom. Give it a swirl, if you like.
- Light a match, blow it out, and drop it into the bottle.
- Immediately seal the bottle.
- Squeeze the bottle hard a few times. A cloud forms as you squeeze and disappears when you release the pressure.
If you don’t have a match, replace the water with rubbing alcohol:
- Pour about a teaspoon of rubbing alcohol into a 1-liter plastic bottle.
- Seal the bottle and swirl around the liquid.
- Squeeze the bottle a few times. When you squeeze the bottle, a cloud forms. When you release pressure, it disappears.
Do not use a match with rubbing alcohol because it is flammable.
How It Works
Squeezing the bottle compresses that gas and increases its temperature. Releasing the bottle lowers the pressure and lowers the temperature. You can see the relationship between pressure, temperature, and volume in the ideal gas law:
PV = nRT
In this equation, P is pressure, V is volume, n is the number of moles of gas, R is the ideal gas constant, and T is the temperature. The amount of gas in the sealed bottle (n) does not change. R is a constant, so it does not change either.
When you squeeze the bottle, you increase pressure. You also slightly decrease volume, but the temperature still increases. Releasing pressure lowers the temperature. The water vapor molecules lose some kinetic energy and draw closer together. Smoke from the extinguished match contains tiny particles that act as condensation nuclei. The water molecules stick to these particles and condense into a liquid.
You can make the cloud thicker by using hotter water. If you don’t have a match, a strip of burning paper works just as well.
Make a Cloud in a Jar with Water, a Match, and Ice
Another way of getting a better cloud holds the gas volume constant and cools the vapor using ice.
- Clear glass jar
- Warm water
- Tray of ice or an ice pack the covers the jar
- Pour warm water into the jar so it fills the jar a couple of inches.
- Swirl the jar or stir the water so the space above the liquid has a lot of water vapor.
- Light the match, blow it out, and drop it into the jar. You’ll see smoke, but no cloud (yet).
- Immediately cover the jar with a tray of ice. A misty cloud forms near the top of the jar, just below the ice. If you have trouble seeing it, slightly lift the tray and watch the wisps of cloud escape the jar.
How It Works
Swirling or stirring the warm water warms the air above the liquid. The warmer air readily absorbs water vapor. When you drop the extinguished match into the jar, the smoke acts as condensation nuclei for cloud formation. But, you need a temperature change as well as condensation nuclei to get a cloud. Instead of changing the temperature using pressure, this method directly cools the air in the jar using ice. Ice chills the air and the cold air near the top of the jar sinks. The warmer air rises and then loses its ability to hold as much water vapor as it cools. The water vapor condenses into a cloud around the smoke particles.
Make a Cloud in a Bottle With Alcohol and a Bicycle Pump
Using a pump gives you more control over pressure so you get a highly visible cloud. Alcohol has a high vapor pressure, so it vaporizes and condenses more readily than water. But, the principle is still the same.
- Foot pump (like a bicycle pump)
- 1-liter plastic bottle
- Rubbing alcohol (isopropyl alcohol)
- Stopper with a hole in it
- Pour some alcohol into the bottom of the bottle. You don’t need a lot. Just add enough so it forms a visible pool (around a teaspoon).
- Swirl it around so it coats the bottle interior.
- Attach the end of the pump to the hole in the stopper. If the hole is too small, use a drill to make it larger. On the other hand, if the hole is a bit large, seal its connection to the pump using tape.
- Seal the bottle with the stopper.
- Pump around 8-10 times. Hold the stopper in place as you pump or else it will pop out.
- Remove the stopper from the bottle and enjoy the cloud.
If the cloud is weak, try the project again, but pump more times to lower the pressure inside the bottle more.
How It Works
Pumping air into the bottle forces the molecules closer together. Releasing the pressure causes rapid expansion of the gas (air and alcohol vapor) and lowers the temperature inside the bottle. The cooling causes the alcohol vapor molecules to stick together and condense. Because alcohol vaporizes more readily than water, more of them are in the gas phase when you release the pressure on the bottle, so you get a denser vapor cloud than you would with water. But, you can repeat the project using warm water instead of alcohol and prove this to yourself. Why warm water? It’s because it has a higher vapor pressure than cold water.
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