Handouts are available below

Big Idea

Here’s another lab I’ve done with my students for the past few years that not only has them practice a useful lab skill – in this case, finding volume using water displacement – it also gets students to practice CER, which stands for Claim Evidence and Reasoning. This lab doesn’t need anything elaborate or complicated – all this lab needs is a ruler, a graduated cylinder, some cubes and prisms and, perhaps, an overflow can if you can get your hands on one.

The activity is made up of 1 big question I want students to investigate and answer: which way of measuring volume – direct measurement, water displacement, or overflow cans – gives the most accurate measurement and which one the least?

Activity: 3 Ways to Find Volume, Practice CER

Before the activity, I go over with students how to find the volume of regular shaped and irregular shaped objects using direct measurement and water displacement. I also show students how to use overflow cans, which is kind of fun if you can find them. An overflow can works similar to the water displacement method with a graduated cylinder. When setting up the overflow can, I first fill it up to the top and let water flow out the straw. When water stops flowing out, it’s ready to use. Now, when an item is dropped in, the volume of that object will cause the water level to rise and water will flow down the straw. I collect and measure the volume of water that overflowed, and this volume of water is equal to the volume of the object dropped in.

For the activity itself, students are given 3 or 4 regularly shaped objects and then asked to find the volume of the objects by using direct measurement, water displacement, and the overflow cans. I get students to fill out a table that looks like this. To answer the lab question, I get students to write a CER statement – complete with evidence and sound explanations. Students need to look at each measurement made for each object and consider which one is closest to the real volume. There is no one agreed upon answer. Some students say water displacement is most accurate because everything is contained in the cylinder, while others will say direct measurement is most accurate because you can make more precise measurements for each side. Some students say water displacement is least accurate because the water inside the graduated cylinder can splash out, while others say the overflow cans are least accurate because the droplets may not all drip down. The great thing is, there are many answers that can be made and we’re having students practice justifying their answers.

That’s how I’m doing it this year and it’s still a work in progress. How do you do it? Please email me a strategy or two – I’m interested to know. 

Thanks for reading, and we’ll talk science again soon.

Resources

Handout(s): Handout – Finding Volume and Practicing CER

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