Videos of the inquiry experiments:
A class meeting and a conversation

In this clip, we are getting ready to weigh oil to find out if it is more or less dense than water, alcohol, and ice, all of which we have weighed in previous experiments. Students are making predictions about what we will find when we weigh the oil, and explaining their predictions.

We go over what we are going to do in the experiment exactly. We review what we did before, and why we weighed 44 milliliters of water, alcohol, and ice in our previous experiments. Students see what the materials will be when they go to the lab.

Right before going to do the experiment, we talk about why we need to weigh the same amount of oil as the amount we weighed of the other materials. The idea of using the same volume so that we can compare the substances is a concrete way for seventh graders to develop an intuition about density: that density has to do with mass and volume, and not mass alone.

Here, students are in the lab, measuring and weighing oil. These two students measure and weigh. Then when they go to record, one student looks back at the value he has for the weight of the same amount of water. He says, "Wait, is that right?" because the value for oil is not what he predicted. He thought it would be heavier than water, and it is lighter. So he goes back and checks to see that he has it right. His prediction and his observation did not agree with each other, and he noticed that when he went to record.

In this clip, students are weighing the empty graduated cylinders and then the oil in the graduated cylinders. Some students are getting help from the teacher, some are helping each other.

When this clip begins, we have collected the data on the experiment. Students told what they got for their measurement and I wrote their data on the overhead. Here we are looking at the numbers, and comparing them to the numbers we have for the experiment where we weighed water, alcohol, and ice.

We discuss the possible reasons that we didn't all get exactly the same number for the weight. We also talk about how we should subtract the value for the graduated cylinder. Up to now, we have compared the different liquids by weighing the same amount of each one in the same graduated cylinder, so that our values are relative. But now, we are beginning to pay attention to the idea of the net amount, and also of how to account for differences in our values.

A colleague interviewed me about the history of this series of experiments, and my thinking about it. In this clip, I talk about the background for the series, and some of the reasons I decided to try it.

In this clip of the interview, I describe the first experiment of the series, an experiment which happens over the course of the whole year as students observe the gradual dissolving of salt in water.

Where the golf ball in salt water is something we observe over the whole year, the ice and alcohol demo is the beginning of a chain of experiments where students generate ideas to figure out why the ice floats in the water and sinks in the alcohol. Subsequent clips continue the interview. Each clip describes another small part of the series of experiments.