Which is Water?

When I was teaching middle school, I really enjoyed using this simple activity to start off our water properties unit. It was a great way for students to work on their observation skills and to create an environment where they could question and be curious.

From a distance, the clear liquids all look the same, but with closer observations, the students can at least tell that one of the liquids is clearly not water. Mineral oil is much thicker, or has a higher viscosity, making it easy to recognize as not water. Viscosity is a great vocabulary word to introduce when describing liquids. P.S. My students would always ask if they could drink the liquids. I always told them we do not drink things in science, and then let them in on a little secret: Mineral oil is used as a laxative!

After students made their initial observations, I explained that I would put ice in each container to give us more data to determine which liquid was water. I did inform them that I used blue food coloring to make it easier for them to see. Once I placed the ice in, I asked the students to draw each container, focusing on where the ice was located in the liquid.

Ice will only float in one of the liquids. This was key in determining which one was water. From there, students wanted to know how I knew that, and it led to a great conversation about water being “weird”, what density is, and how to calculate it. If you don’t know, I Love Density (see the image below) is a great way to help students remember the formula for density. This was an activity that I could reference back to throughout different lessons. Check out the full YouTube video under the STEM tab to see how you can use this simple activity for a variety of age groups.