# Cartesian Diver

## Assessment for density and or pressure, observation, and use of evidence

### Procedure

Create a Cartesian Diver with a capped two-liter pop bottle. Filled with water and a glass eye-dropper in it.

When the bottle is squeezed the dropper moves to the bottom and when the pressure is released the dropper moves to the top.

Ask - How did the stopper go up and down?

Ask - What caused the stopper to go up and down?

### Summary of a Cartesian Diver Results

The following is a list of results summarized from the least scientific to the most scientific.

• Described the cause as intentions of an object. It wanted to sink. The water wanted it to float. The water made it happen. The water pushed the air out so it would sink.
• Described the cause from an observation of what they observed. Observation of the diver. It sunk or it floated. Observation of the bottle or hands. It was squeezed. Observation of the water or the air inside the diver. The water went in and out of the diver. The air went in and out of the diver.
• Described the cause of the event as a result of an interaction with one variable. The diver sunk because the water made it heavier. The diver floated because the air went back in and made the diver lighter. When the bottle was squeezed the water and air went in and out to make the diver sink and float.
• Described the cause of the event as a result of two variables. The diver sinks or floats because of how the size and weight change. The amount of water in the diver changes to make it heavier and lighter. But the size of the diver doesn’t change.
• Described the cause of the event as a change of relationship between two variables. The volume of the diver stays pretty much the same when the bottle is squeezed. However, the air is compressed which allows more water to go into the diver and makes it heavier. It doesn’t float or sink just because it is heavier. It is because it is heavier for its size (volume). I think the density is changing.