Do you know what happens when you fill up a bottle with any gas? You can put more and more gas in, but the pressure will keep increasing until <<pow!>> at some point the lid will blast off or the bottle can even explode!
In this experiment, we’ll use the explosive power of gas under pressure to blast rockets into the air and who knows, maybe all the way into space!
You’ll be making a rocket that will be powered by nothing more than a piece of dry ice (frozen carbon dioxide) in water. In this experiment you’ll get to see how frozen CO2 can sublimate, or change from a solid state directly to a gas state without passing through a liquid state. While solid, the CO2 fits nicely in your bottle with room to spare, but in a gas state, it will expand under pressure until it can’t fit in the bottle anymore.
You’ll also be able to explore the physics principle that every action has an equal and opposite reaction. As the pressurized gas pushes your cork out of your bottle, the cork will also push back on the gas in the bottle, causing it to shoot up into the air.
Remember: CO2 freezes solid at a temperature of –78.5˚C, making it super cold and dangerous to touch with your bare hand. Never touch dry ice with your skin – always use tongs to handle it!
What do you think will happen?
Since you’re making a rocket, make a prediction – how high up do you think your rocket will fly? Write it down and check if you were right after the experiment. How long do you think it will take for the gas to build up in the bottle before the rocket fires? Write down a prediction of this too!
What to Use
- dry ice (frozen CO2; usually available at chemistry supply stores and also businesses that ship their products cold)
- a cork
- a plastic bottle, 1-2L capacity (make sure the cork fits snuggly in the mouth of the bottle)
- card paper, tape, plastic, hot glue, coloured markers etc. for decorating your bottle
- a manhole cover or sewer grate (make sure the cork fits snugly into one of the holes so that it will be held in place)
- stopwatch (optional)
What to Do
STEP 1 – Make a Rocket
a) Do a quick Internet search for rockets. You’ll see that many have pointy noses to help them shoot through the air, and fins on the back to stabilize them. Remember that your rocket will be a bottle that will shoot a cork out from its mouth, so it’s the flattish bottom that will fly through the air. If you want to make it fly more aerodynamically, try attaching a nose cone (made from stiff paper or plastic) and fins. Don’t forget to make your rocket beautiful!
STEP 2 – Scout a Launch Pad
b) The easiest way to fire the rocket is to put the cork in its mouth, then turn the bottle over and plant the cork firmly into one of the small holes in a manhole cover or one of the slots in a sewer grate. Look around for a perfect fit BUT also remember that you can’t control which way your rocket will go after it’s fired. Find a safe place where there is nothing around that can be broken, and a place where you will be safe – not in the middle of a street!
STEP 3 – Ready, Aim, Fire!
When it’s time to fire your rocket, make sure you have an adult helping and supervising to help you stay safe!
c) Clear the area around the launch pad. Fill your bottle about ¼ full with water. Prepare your cork, tongs, and dry ice (which should be in a bucket or any safe container). When everything is ready, act quickly! It’s as easy as:
1 – Use tongs to drop 1-2 pieces of dry ice into the bottle.
2 – Turn it over and cork it.
3 – Turn it over again and jam the cork into the planned hole. Run for cover!
If you have a stopwatch, start it and watch as the dry ice bubbles furiously in the water and the bottle starts to look like it’s bulging. Are you ready for blast-off?
What Did You Find?
What happened? Did your rocket fly as high as you had hoped? Did it leave the atmosphere and disappear into space? Remember, as long as you can collect all the parts you can keep firing your rocket until you run out of dry ice.
For more fun, invite your friends to make rockets and join you!