If you were to take another air-filled balloon and squeeze it in your hands, what would happen,

In this activity, students learn about Newton’s Third Law by making balloon rockets.

Using a balloon, we can create a good demonstration for the type of propulsion that moves a rocket. When we inflate a balloon, we fill it with a pressurized gas (air). When we let go of the end, the air rushes out and pushes against the air around the balloon to move it in the opposite direction. 

Newton describes this effect in his Third Law of Motion: for every action, there is always an equal and opposite reaction. The gas rushing out of the rocket or balloon is the action and the movement of the object in the opposite direction is the reaction.

Because balloon openings are wobbly, the flight path of a balloon is wobbly, too. The air escaping the balloon (the action) pushes out in every which way and the reaction of the balloon is to move in every which way, too.

One way to stabilize the direction of the balloon is to attach it to a simple track made of string. Once attached to a straight path, it’s easier to see the direct relationship between the size of the action (the amount of air escaping the balloon at once) and the resulting size of the reaction (the distance the balloon travels).

The activity described below works well for all students. The student with a visual impairment can best experience the activity as the person who has a chance to release the balloon*. Also beneficial is an opportunity to be at the end when the balloon rocket arrives. The whole class will want to do this activity again and again.

*NOTE: Balloons should NOT be used by students with latex allergies. If in a latex-free school, use mylar balloons.

Action force - force acting in one direction

Reaction force - force acting in the opposite direction

Forces always act in pairs. The two forces act in opposite directions. When you push on an object, the object pushes back with an equal force. Imagine a person sitting in a rolling chair at a desk. When the person sitting in a rolling chair pushes on the desk, this push or force is the action force.

Now, the desk pushes back against the person with a force of the same size. This reaction force will cause the rolling chair to move backwards. Notice that the two forces act on different objects. The action force acts on the desk. The reaction force acts on the person.

Newton’s third law of motion describes action and reaction forces. The law states that for every action force, there is an equal and opposite reaction force. Imagine hitting a tennis ball. The racket exerts a force on the ball. This is the action force. The ball exerts an equal and opposite force on the racket. This is the reaction force.

Newton’s third law explains how many sports injuries are caused. The more force you use to a hit a tennis ball, the more reaction force your arm receives from the racket. Every time your feet hit the ground when you are running, the ground hits your feet with an equal and opposite force.

Newton’s third law explains how balloons and rocket engines work. When the neck of an inflated balloon is released, the stretched rubber material pushes against the air in the balloon. The air rushes out of the neck of the balloon. The action of the air rushing from the balloon pushes against the balloon, moving it in the opposite direction.

When rocket fuel is burned, hot gases are produced. These gases expand rapidly and are forced out of the back of the rocket. This is the action force. The gases exert an equal and opposite force on the rocket itself. This is the reaction force. This force pushes the rock upward.

Can you blow up a balloon without using your mouth? In this simple science experiment, we’re going to show you how to do it with only a few everyday items you probably already have in your home. It makes a great experiment for young children because the set-up is simple and it only takes a few minutes to get to the exciting finale.

In addition to a video demonstration and detailed printable instructions, we also have the scientific explanation of how this simple chemical reaction works making it perfect for older scientists too.

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

Supplies Needed

• Small Soda Bottle
• Balloon
• Baking Soda
• Vinegar
• Funnels
• Teaspoon

BALLOON BLOW UP SCIENCE EXPERIMENT INSTRUCTIONS

Step 1 – Start with some questions: How do you blow up a balloon? What if I told you that you couldn’t blow air into it, do you think you could still inflate (blow-up) the balloon? Then observe the supplies for the experiments. Do you think they can be use to blow up the balloon? If so how? Write down your hypothesis (prediction).

Step 2 – Using a funnel, pour about a third of a cup of vinegar into the bottle. We used Apple Cider Vinegar, but any type of vinegar will work.

Step 3 – Then insert another funnel into the mouth of the balloon. We recommend using two different funnels. One funnel for filling the bottle with vinegar and one for the balloon. However, you can do the experiment with only one funnel. Just make sure you completely wash and dry the funnel after you add the vinegar and before you put it into the balloon. This is very important.

Step 4 – Place two teaspoons of baking soda into the funnel so it falls into the balloon. When the balloon is filled with the baking soda, carefully remove it from the funnel. 

Step 5 – Next, secure the mouth of the balloon over the mouth of the bottle. Take your time doing this and don’t let any of the baking soda fall out of the balloon and into the bottom of the bottle. Take a moment to make some observations. What will happen if we lift up the balloon? Write down your hypothesis (prediction) and then test to see if you were right!

Step 6 – While holding the bottle, lift the end of the balloon and allow the baking soda to drop into the bottle. 

Step 7 – What happens to the balloon? Was your hypothesis correct? Wondering what caused the balloon to inflate? Find out the answer in the how does this experiment work section below.

Video Tutorial

Watch the Balloon Blow Science Experiment Step by Step Instructions

How Does the Science Experiment Work?

When baking soda (a base) and vinegar (an acid) are mixed together they create a chemical reaction that results in the formation of carbon dioxide gas. Gases do not have a specific shape or volume, rather they expand rapidly filling their container. Gases expand rapidly because their particles move at high speeds in all directions. As the carbon dioxide gas fills the bottle, it has nowhere else to go so it begins to fill the balloon. As the carbon dioxide gas fills the balloon, the balloon inflates. The more gas that is created, the larger the balloon will inflate.

The baking soda and vinegar chemical reaction will continue to inflate the balloon as long as there is still baking soda and vinegar to react. Once the reaction between baking soda and vinegar has stopped, the balloon will slowly begin to deflate.

An acid is a substance that tastes bitter, reacts with metals and carbonates, and turns blue litmus paper red.

A base is a substance that tastes bitter, feels slippery, and turns red litmus paper blue.

Other Ideas to Try

Does changing the amount of baking soda and vinegar change the size of the balloon when it inflates? What would happen if you used another acid like lemon juice instead of the vinegar? Would it react the same with the baking soda?

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