Science Experiments / Week 2
Week 2 of 6
Chemical Reactions
Big question
What happens when two things mix together and make something brand new?
- Balloon Gas Reaction
- 45-60 minutes
This week follows the science loop
AskPredictTestObserveExplainImprove
The big idea
- Some mixtures do not just sit together - they react and make something new.
- Baking soda and vinegar react to make a gas called carbon dioxide.
- Bubbles and gas can be evidence that a chemical reaction happened.
When you mix sand and water, you still have sand and water - you could dry it out and get them back. That is just a mixture. But some things do something different when they meet: they react and make a brand-new substance that was not there before. Baking soda and vinegar do exactly this. When they touch, they react and make carbon dioxide, a gas you cannot see. This week you will trap that gas inside a balloon. The fizzing and the balloon puffing up are your evidence that a real chemical reaction happened - not just a mix.
Words to know
- Chemical reaction
- When substances combine and change into something new.
- Gas
- A form of matter, like air, that spreads out to fill its space.
- Carbon dioxide
- The gas made when baking soda and vinegar react. It is in the air too.
- Evidence
- What you see or measure that shows something really happened.
- Matter
- Anything that takes up space, including solids, liquids, and gases.
Materials
- 1 tablespoon of baking soda
- About half a cup of white vinegar
- A balloon
- An empty plastic water bottle
- A small funnel, or a piece of paper rolled into one
- A measuring spoon
Safety
- Vinegar can sting eyes - keep it away from faces and do not splash it.
- Never drink the vinegar or eat the baking soda.
- An adult should help stretch the balloon over the bottle.
- Do this over a sink or tray, and wipe up spills so no one slips.
Experiment: Balloon Gas Reaction
Predict first
Before you touch any materials, write down what you think will happen in this experiment - and why. Making a prediction first is what turns building into science. You will compare your prediction to what you actually observe.
Steps
- 1
Ask: Can two things you mix make enough gas to blow up a balloon? That is your question.
- 2
Pour about half a cup of vinegar into the empty bottle.
- 3
Use the funnel to put 1 tablespoon of baking soda inside the balloon.
- 4
Predict: How big do you think the balloon will get? Draw or write your prediction first.
- 5
Stretch the mouth of the balloon over the top of the bottle, but keep the baking soda up in the balloon so it does not fall in yet.
- 6
Test: Lift the balloon straight up so the baking soda drops down into the vinegar.
- 7
Observe: Watch the mixture fizz and the balloon fill up. Notice how big it gets compared to your prediction.
- 8
Improve: Try again with a little more or a little less baking soda and see how the balloon size changes.
Why it happens
Baking soda and vinegar are made of tiny pieces. When they meet, those pieces rearrange and form new substances - one of them is carbon dioxide gas. A gas takes up much more space than the liquid did, so it rises up and fills the balloon. The fizzing bubbles you see are that gas escaping the liquid. Because a brand-new substance is made, this is a chemical reaction, not just a mixture.
How engineers use this
Engineers and bakers use gas-making reactions on purpose. Baking soda is what makes bread, muffins, and pancakes rise - the carbon dioxide makes tiny bubbles inside. Some fire extinguishers and party poppers also use fast gas reactions. Controlling how much and how fast is an engineering job.
Related project
Want to see the same reaction on a bigger scale? Build a baking-soda volcano - it uses the exact same carbon dioxide reaction you made in the balloon.
What did you notice?
Look back at your prediction and your results, then talk these through together.
- What did you see, hear, or feel that tells you a reaction happened?
- Where did the gas that filled the balloon come from?
- Was the fizzing a new thing, or was it just the baking soda and vinegar mixing?
- What do you think would happen with twice as much baking soda?
Reflect
Write or draw what happened to the balloon, and explain in one sentence where the gas came from.
Mini challenge
Figure out the amounts of baking soda and vinegar that fill the balloon the biggest without popping it.
Want to go further?
Test whether warm vinegar makes the reaction go faster than cold vinegar. Keep the amounts the same so it is a fair test.
Before you finish
- I predicted how big the balloon would get.
- I mixed the baking soda and vinegar safely.
- I observed the fizzing and the balloon filling up.
- I can explain that the gas is carbon dioxide made by a reaction.
- I tested a new amount to see what changed.
Finished the experiment and your reflection? Mark this week complete to track your progress through the 6-week course.
Lab journal
Write your own science notes as you go - they follow the same loop you used this week. Notes are saved on this device only; nothing is sent anywhere. You can also print this lesson and write by hand.
What did you want to find out?
What did you think would happen, and why?
What one thing did you change to keep it a fair test?
What did you see, hear, or measure?
Use what you noticed as your evidence.
What would you change to make it work better?
Draw what happened
Sketch your experiment or your improved design, and circle the part you changed.