Science

Exploding and Growing Ziplock Bags with Dry Ice

by dontregartha November 3, 2017

This is a quick and simple, but spectacular, demonstration requiring just a few items of equipment.

 

Learning outcomes

You will be able to:

  • Describe the reaction of dry ice with air, water and soap solution.
  • Provide an example of a substance that sublimates.
  • Discuss the impact of changes in temperature on the rate of a reaction.

You will need (per demonstration):

  • A shallow Gratnells (F1) tray
  • Large zip lock sandwich bags (for as many repeats/variables as you wish to test)
  • Half a cup of dry ice (with thanks to dryicesupply.co.uk) per repeat
  • Half a cup of warm water
  • Half a cup of warm washing up liquid solution (solution of 70:30 warm water to washing up liquid)
  • A timer/stopwatch
  • A transparent Perspex/protective screen or hood (if you want to observe the reaction more closely)

What to do:

Take a look at our exploding and growing zip lock bags with dry ice video.

Demo 1

  • Place an opened zip lock bag in the middle of a shallow Gratnells tray.
  • Add half a cup of warm washing up liquid solution to the bag followed by half a cup of dry ice and immediately seal it closed.
  • Step well back and observe what happens.

Demo 2

  • Place an opened zip lock bag in the middle of a shallow Gratnells tray.
  • Add half a cup of warm water to the bag followed by half a cup of dry ice and seal it closed.
  • Step well back and observe what happens.

Demo 3

  • Place an opened zip lock bag in the middle of a shallow Gratnells tray. Add half a cup of dry ice to the bag and seal it closed. Step well back and observe what happens.

Tip: Perform these demonstrations in reverse order, i.e. demo 3 first. Demo 3 is the slowest, it provides plenty of opportunity to observe and discuss what is happening. The observers can time the reaction from the addition of the dry ice to when the bag pops and note down the result. You can discuss and make predictions as to what will happen in demo 2 and again for demo 1. You may wish to introduce an additional demonstration between demo 1 and 2 using cold water.

What is happening?

Dry ice is a solid form of Carbon Dioxide (CO2), it is very cold, less than -70 degrees Celsius. At room temperature, it sublimes (turns directly from a solid to a gas) and is visible as fog/smoke. When dry ice is placed into a sealed bag at room temperature it sublimes relatively slowly (demo 3). Gaseous CO2 is released and fills up the bag. The pressure of the gas inside the bag increases as more gas is produced in a fixed volume of space. When the bag is full it stretches slightly then bursts.

Adding warm water speeds up this reaction, gas is released more rapidly, the bag fills more quickly and the pop when the bag explodes may be louder. It takes less time for the bag to fill and pop. Why does warm water speed up the rate of reaction? Warm water increases the amount of energy available to the reaction and causes the dry ice to sublime more quickly. What happens if you use cold water instead?

Adding washing up liquid solution results in the gaseous CO2 released on sublimation becoming trapped inside the bubbles, the bag fills up with gas and bubbles until it explodes with a pop! As the bubble burst, or if you burst them, you will see clouds of gas being released.

Other things to try and questions to consider…

  • Start a stopwatch when the bag is sealed and stop it when the bag goes pop.
  • How long does it take under each set of conditions for the bag to explode?
  • Is warm water better (quicker pop) than cold water?
  • How many repeats should you carry out?
  • What variables do you have to control to ensure a fair test?

Health & Safety

As with all Gratnells Learning Rooms What’s In My Tray activities, you should carry out your own risk assessment prior to undertaking any of the activities or demonstrations. In particular, take care when using dry ice, consult the relevant CLEAPSS guide, wear appropriate personal protective equipment and ensure adequate ventilation to prevent unsafe build-up of CO2.