Maybe I should have saved this activity for last because it might be the coolest of the five science investigations in the set. It looks a little messy, but it doesn’t have to be. And it’s totally worth it because when you drop in the Alka Seltzer tablets, the fun begins!
The Lesson
In this lesson, the children discover that oil and water don’t mix and they learn why. As they observe the water sinking and the oil floating, they also begin to understand that different liquids have different weights. The next part of the investigation includes a chemical reaction, so we use red food coloring and sequins to make the reaction more easily observable. Adding an antacid, like Alka Seltzer, releases carbon dioxide into the liquid allowing the water to float and sink inside the bottle… a lot like lava lamp bubbles do. It’s pretty cool!
Teaching Options
Depending on your budget, this science investigation can be done as a teacher-demonstration with just one large soda bottle. However, if you can get donations, it’s more engaging if small groups or each individual can make their own. Baby oil is nice and clear, but you can keep the cost down by using store-brand cooking oil instead. 2020 UPDATE: The last time we did this lesson, I used clear plastic cups and vegetable oil. It was cheaper and easier to manage the materials which allowed me to plan for one set-up per team of children.
Instructional Materials
The directions for this investigation, along with the student recording sheets and anchor chart pages, can be found in my Valentine Science pack.
Happy teaching!
