chemical and physical reactions balloon experiment

Blowing up a balloon with effervescent vitamin tablets or popping candy is a fantastic, visual and fun way to introduce the concept of chemical and physical reactions, and irreversible changes to children. These substances release a gas ( carbon dioxide ) when they are placed in water. The carbon dioxide cannot escape from the container and so starts to blow up the balloon showing just how much gas has been released.

Carbon Dioxide or CO2 is a gas produced when people and animals breathe out, or when carbon is burned.

Children can be encouraged to predict which substance will blow up a balloon most effectively, drawing on their existing knowledge or by asking questions to gather information in order to make their prediction.

This activity can easily be turned into a an investigation to encourage children to think about planning scientific enquiries, controlling variables, setting up a fair test, taking measurements, making predictions, recording and presenting data and finding scientific evidence to support ideas.

Chemical and Physical Reactions Experiment Ingredients


Small, clear bottle

Effervescent tablets such as some vitamin supplements (take extra care to ensure safety when using these products)

Popping candy



Stopwatch – optional



Blow up the balloons first and then let the air out. This makes them blow up more easily during the activity.

Fill the small bottles or jars with water, leaving a gap at the top.

Add an effervescent tablet to one bottle and popping candy to another before quickly placing the balloons on the top of the jar. Make sure there are no holes or the gas will escape.

Observe the balloons blowing up.

Blown up balloon

Why did this happen?

Popping candy is made by heating the ingredients and then exposing to carbon dioxide at very high pressures before cooling, this traps tiny bubbles of gas inside the popping candy. When popping candy is exposed to water the sugar dissolves and releases carbon dioxide. In this activity the carbon dioxide fills the available space in the jar and then starts to fill the balloon, blowing it up.


Effervescent tablets contain sodium bicarbonate (baking soda) and citric acid. When you drop a tablet into water they form sodium citrate, water and carbon dioxide, which is the bubbles of gas you see. The bicarbonate of soda reacts with the citric acid, this is an acid – base reaction just like we see when we add vinegar to baking soda.

Both the Effervescent tablets and popping candy release carbon dioxide when added to water, but a different type of change occurs with each. The popping candy and water is an example of a physical change as the carbon dioxide is not formed during the reaction, just released and the popping candy dissolves into the water. Effervescent tablets reacting with water is a chemical reaction as new chemical substances are formed.


Extension Ideas

Investigate what happens if warmer water is used, does the chemical reaction slow down or speed up?

Children can try to record the time taken from the beginning to the end of the each reaction.

Investigate whether using baking soda and vinegar would produce enough gas to fill the balloon. This is another example of an acid-base chemical reaction which releases carbon dioxide.


Learning Outcomes

Key stage 1  – Science – Working Scientifically

Key stage 2  – Science – Working Scientifically

  • Setting up practical enquiries and fair tests.
  • Gathering, recording and presenting data.
  • Using results to draw conclusions.
  • Using scientific evidence to answer questions.

Key stage 2 –Science – States of Matter

Key Stage 2 – Science – Properties and changes to Materials

The reaction between the effervescent tablets and water is a good example of an irreversible change.


This post was written by Emma of Science Sparks

emmavEmma is a busy Mum to three who is passionate about science education. You can find Emma’s experiments and activities over at Science Sparks which is full  of fun, creative and engaging science based activities for children of all ages, perfect for home or school. Find out more at Science Sparks:



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