One of the earliest homeschool science lesson plans is about states of matter. Solids, liquid, and gas (plus plasma and Bose-Einstein condensate) are the first states of matter that are covered in an elementary science curriculum, and of those, gasses are often the hardest for the kids to conceptualize simply because they’re harder to see. In this lab, however, the kids get up close and personal with the creation of gas. Remember, gas can be a product of a chemical reaction, and that’s exactly what we’re going to do here.
This homeschool science lesson plan is pretty safe but, as a precaution, kids should be wearing eye protection. Check out the full list of lab safety rules.
1 empty water bottle per child
1 large balloon per child
paper (or plastic) funnel
measuring spoons from your chemistry kit
- Ask the kids to measure 20 mL of vinegar (acetic acid) and pour it into the water bottle. Set this aside.
- Pre-stretch a balloon. If the balloon plastic is thick or not very stretchy, this lab may not work well. Giving the balloon a few stretches first will help it along.
- Insert the end of the funnel into the open end of the balloon.
- Measure 15 mL (1 tbsp) of baking soda and pour it into the funnel and into the balloon.
- The next bit gets tricky so you’ll need to help. While holding the balloon with the baking soda in it BELOW the opening of the water bottle, stretch the balloon opening over the mouth of the water bottle. Be careful not to dump any of the baking soda into the water bottle.
- BEFORE you dump the contents of the balloon into the water bottle, ask the kids what they think might happen. What is their hypothesis?
- Ask the kids to lift up the top of the balloon and dump the baking soda into the water bottle.
Now for the fun part. If you’ve used a clear water bottle, you should be able to see the reaction between the baking soda and the vinegar. There will be lots of bubbles, and, if you’re balloon isn’t too tight, the balloon should expand as the gas fills the balloon.
Acetic acid, or vinegar, reacts with baking soda to create a gas. In this case, it is carbon dioxide. However, most people aren’t aware that there’s another reaction happening here, before the carbon dioxide is created. At first, the vinegar and baking soda react to create carbonic acid which, because it is so unstable, breaks down quickly into carbon dioxide and water. The gas escapes the water because it is denser, in the form of bubbles.
Interestingly, and we’ll do another homeschool science lesson plan later on to show this, carbon dioxide is heavier than the air we breathe, so it collects and hovers just over the surface of the water. In this case, it displaces the air in the bottle, pushing it up into the balloon. The more carbon dioxide we create, the more air we displace and the bigger the balloon will get.
With supervision, this is a great lab for the kids to experiment with. They can try:
- different amounts of baking soda and vinegar
- they can try using a different acid like citric acid
- they can change the temperature of the water or the vinegar
- they can add the baking soda to the bottle more quickly or slowly
- use a different size water bottle or balloon
- or see what other things they come up with!