Science

Self Inflating Balloons

by Amy Collins July 19, 2018

You will need:

• 1 Gratnells shallow (F1) tray
• 1 bottle of distilled malt or white vinegar (568ml)
• 1 pot bicarbonate of soda (200g)
• 1 packet multicoloured balloons
• 1 empty, clean, plastic drinks bottle ~400ml capacity (great opportunity for reusing bottles destined for recycling, flat bottomed bottles are the most stable for this activity)
• 1 funnel
• 1 teaspoon
• 1 black marker pen (optional)
• Safety glasses and lab coat (if you get carried away and add too much of the reactants, the balloon may pop off and splatter you!)

What to do:

1. Work in the Gratnells shallow (F1) tray to catch any spills and contain any mess.
2. Using the funnel if you need to, pour ~50ml vinegar into the empty plastic bottle.
3. Place a balloon over the end of the funnel and hold it there with your fingers.
4. Add two heaped teaspoons of bicarbonate of soda to the funnel and tap it down into the body of the balloon.
5. Place the mouth of the balloon over the entire rim of the bottle and make sure it is well down over the neck/ridges.
6. Make a prediction as to what you think will happen when you add the bicarbonate of soda to the vinegar.
7. When you are ready to start the reaction, lift the body of the balloon up so the bicarbonate of soda falls out the balloon and into the vinegar. You may need to keep hold of the bottle if it starts to wobble.
8. Repeat the activity as many times as you like. Before they are filled with bicarb, you could draw funny faces or messages on the balloons using a marker pen and they will be revealed as the balloons are inflated.

What is happening?

When vinegar and bicarbonate of soda are mixed together a chemical reaction occurs and carbon dioxide and water are produced. Carbon dioxide is a gas. The production of carbon dioxide inside the closed system increases the pressure (more molecules in the same space), forcing the balloon (which is more elastic than the bottle and so offers the least resistance) to expand to contain the gas.

This is the chemical reaction.
Vinegar (Acetic Acid) + Bicarbonate of Soda (Sodium Bicarbonate) → Carbonic Acid + Sodium Acetate

Carbonic acid is unstable and immediately breaks down to form water and carbon dioxide, which are the end products of the reaction along with sodium acetate (a type of salt).

Other things to try……

• Try taking the temperature of the vinegar/liquid in the bottle before and after the reaction. What has happened?
• Use the marker pen to draw a 1cm long black line on the balloon before adding the bicarbonate of soda. Repeat the activity and time how long it takes for the line to expand to 5cm in length.
• Experiment with different amounts of bicarbonate of soda, e.g. 1 teaspoon, 2 teaspoons and 3 teaspoons. Does this effect how long it takes the line to get to 5cm in length?
• Experiment with the temperature of the vinegar. e.g. straight from the fridge v’s room temperature. Does this effect how long it takes the line to get to 5cm in length?
• While experimenting, remember to keep all other variables the same.

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.