Name: __________________________________ Class: ______________________ Date: ____________

Introduction: Some air masses on Earth are warm, wet, and have a low density. We call them “low pressure systems.” On the other hand, some air masses are colder, dryer, and heavier. We call these “high pressure systems.” So what happens when the two meet? That’s where it gets interesting. Usually, the heavier air will slide beneath the warmer, wetter air. And when warm, wet air is pushed skyward, it cools off. The water vapor then condenses, forming clouds of droplets. And if those droplets get heavy enough… grab your umbrella.

Unfortunately, this process is hard to simulate in the lab. Condensation requires large temperature changes, which take time. And unless you want a foggy classroom, we can’t use regular air either. Luckily, both of these problems can be solved with a plastic bottle and a regular old bicycle pump.

Materials:- a two-liter bottle - one bicycle pump with needle - cold water - hot water- one rubber stopper with small hole - one graduated cylinder - tap water - rubbing alcohol

Procedure:1. Fill plastic bottle with 3 ml of cold water. Cap bottle and shake ten times to spread out liquid.2. Insert rubber stopper (attached to pump) into 2-liter bottle. Press firmly.3. Turn on pump for designated amount of time. Quickly remove rubber stopper. Observe the result.4. Repeat steps 1-3 with various liquids and varying amounts of pressure, as described below.

Results:

Typeof Liquid

Amountof Pressure Observations

Cold Water 6 seconds (10 psi)

Cold Water 12 seconds (20 psi)

Hot Water 6 seconds (10 psi)

Hot Water 12 seconds (20 psi)

Tap Water 6 seconds (10 psi)

Tap Water 12 seconds (20 psi)

Rubbing Alcohol 6 seconds (10 psi)

Cloud ina Bottle

Lab

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Rubbing Alcohol 12 seconds (20 psi)

Post-Lab Conclusions: 1. Which of the three types of water produced the most condensation? Why?

2. Why did rubbing alcohol produce more condensation than water?

3. Why did the water vapor suddenly condense when the rubber plug was removed?

4. How is this lab similar to the way that clouds form? How is it different?

5. Label the arrows below regarding phase changes.

6. Why does water condense when it cools down? *Hint:

7. Make a prediction about what will happen in the diagram below. Include mention of density, humidity, and temperature. Include time calculations as well.