What happens to the balloon inside the bottle

What you Need

• 2 balloons
• a clear plastic water bottle
• scissors
• thumbtack or nail

What to Do

1. Take one of the balloons and cut off the bottom part, leaving you with only the top part that may resemble a very small swim cap.
   

2. Using the thumbtack or nail, poke a hole in the bottom. The hole doesn’t need to be too large, about 2 -3 mm.
   

3. Cover the bottom of the water bottle and the hole that you just poked with the balloon you cut in step 1.
   
   
   
4. Take the other balloon and put it inside the bottle. Then fold the bottom of the balloon around the rim of the bottle so the balloon hangs from the top.
   

5. Pull on the bottom balloon membrane and watch what happens to the balloon inside the bottle.
   

6. Let go of the balloon membrane and observe what happens to the balloon inside the bottle.

You should see the balloon inflate as you pull out on the membrane and deflate as you let go of the membrane. What causes this? Is there a ghost blowing into the balloon? Nope! It’s just physics!

What’s Going On?

Did you know that right now you have 14.7 pounds pushing against every square inch of your body! That would be like having every square inch of your body sandwiched between a pair of newborn twins! That’s right, in our atmosphere there is pressure whichis an effect that occurs when a force is applied on a surface. So why don’t you feel like you are “under pressure” all the time? When the inside of you is pushing out as hard as the outside is pushing in, the forces balance and you feel nothing. But what happens if one side stops pushing as hard? Turns out that is how we can breath!

Air pressure comes from teeny-tiny gas particles that are floating around, bumping into each other and bumping into you. The particles will take up whatever space is available to them, until they run into an object or a wall. Inside the plastic water bottle there are a bunch of gas particles bouncing off the walls of the bottle and filling up the space. When you pull down on the balloon membrane, you make the space inside the bottle larger, which gives the particles more room to move around. If the particles have more room to move around, they won’t exert as much pressure on the walls; they won’t bump into things as often. When you increase the volume (the amount of room) you decrease the pressure inside that space, this law of physics is called Boyle’s Law.

As the bottom balloon is pulled down, the volume increases and the pressure decreases. But, the pressures on the inside and outside of the bottle must balance. The only way to keep the pressure inside the bottle the same as the pressure outside of the bottle is to decrease the volume again. The only thing that can move to do that is the balloon on top, so it expands.

This is how are lungs operate. Inside our bodies, at the base of our lungs there is a membrane called the diaphragm. When you inhale, your diaphragm contracts and flattens out, increasing the volume and decreasing the pressure in your chest. Because you have more room air gets sucked in through your mouth and nose and into your lungs, just like it did in the balloon, and then your lungs fill with air. Your lungs are like the balloon and the diaphragm is like the balloon membrane at the base of you bottle. When you exhale your diaphragm relaxes which decreases the volume of your lungs and increases the pressure in your chest. To make sure that your chest doesn’t explode, the air gets forced back out through your mouth and nose.

Try This!

• Try doing the experiment with a larger bottle and larger balloons. Does it change how the inside balloon reacts?
• Try pushing the membrane in. What happens to the balloon inside the bottle?
• Put your hand on your stomach. When you breathe in you should feel your stomach expand. Why does it do this?

More Information

Can science blow up a balloon?

In this easy science experiment, kids can explore how matter behaves when heated and cooled. Watch our demonstration video, gather your materials, print out your instruction sheet to get started. Then, discuss your findings with our easy to understand explanation of how it works below.

JUMP TO SECTION: Instructions | Video Tutorial | How it Works

Supplies Needed

• 8-inch Balloon
• Empty 2-Liter Bottle
• 2 pans (I used 9-inch square pans)
• Enough Ice & Cold Water to Fill one Pan
• Enough Hot Boiling Water to Fill another Pan

Use a Bottle to Blow-up a Balloon Science Experiment Instructions

Step 1 – Start with an empty two-liter bottle and secure a balloon around the mouth of the bottle. Helpful Tip: 8-inch balloons work best for this experiment. When we tried this with a 10-inch balloon, it didn’t inflate entirely.

Step 2 – Prepare two pans of water. Fill one pan with ice and cold water. Fill the other pan with hot boiling water. What do you think will happen if you place the bottle in the pan with the hot water? What do you think will happen if you place the bottle in the pan with the cold water? Write down your hypothesis (prediction) and then follow the steps below.

Step 3 – Place the bottle in the pan with the hot water. Hold it in the pan for 30-40 seconds. Watch what happens to the balloon and make some observations. Does the balloon inflate? What do you think will happen if you remove the bottle from the pan with the hot water?

Step 4 – Remove the bottle from the hot water and place it on the table for a few seconds. Notice that the balloon stays inflated. What do you think will happen if you put the bottle in the pan with the cold water? Is this different than your first prediction?

Step 5 – Place the bottle in the pan with the cold water. Hold it in the pan for 30-40 seconds. Watch what happens to the balloon and make some observations. Does the balloon deflate? What do you think will happen if you remove the bottle from the pan with the cold water? 

Step 6 – Remove the bottle from the cold water and place it on the table. The balloon will remain deflated.

Do you know the why the balloon inflated and deflated throughout the experiment? Find out the answer in the how does this experiment work section below.

Video Tutorial

How to Blow Up a Balloon with a Jar Science Experiment Step by Step Instructional Video

How Does the Science Experiment Work

Even though the bottle looks empty, it is actually filled with air. By placing the balloon on top of the bottle, you trap the air inside of the bottle. This experiment is a great way to show how matter behaves when it is heated and cooled. Matter expands (gets bigger) when heated and contracts (gets smaller) when cooled.

When the bottle is placed into the pan of hot water, the heat from the water causes the air inside the bottle to heat up. As the air in the bottle heats up, the molecules of the air begin to move faster and take up more space. The air from the bottle then moves into the balloon causing it to inflate.

When the bottle is removed from the hot water, the balloon will stay inflated. This is because the air molecules in the bottle are still hot. If you leave the bottle out of the water for a while, it will eventually cool down. When the air in the bottle cools down, the molecules of air slow down, move closer together, and take up less space. This will cause the balloon to deflate.

When the bottle is placed into the pan of ice-cold water, the cold water causes the air inside the bottle to cool down. As the air in the bottle cools down, the molecules of the air slow down and take up less space because they move closer together. The air then moves out of the balloon and back into the bottle, causing the balloon to deflate.

More Science Fun

Want to learn more about what air can do? Then check out these other simple and fun experiments:

I hope you enjoyed the experiment. Here are some printable instructions: