A Perfect Season for Poetry

Aayush and Shaurya share their Leaf Fish and their poems with you.

Sinking and Floating

This post shares the design thinking behind a boat race used to learn more about the concept of floating and sinking. Design thinking and collaboration resulted in rapid growth in vocabulary. Personal questions lead to group questions that promoted higher levels of thinking and a fascination for their subject material.

The students share with you excerpts from their explanations and presentations.

Aaron Wrote:

Why do some things float while others sink?

The experiments we carried out helped us to understand and explain this.

To explain what density and volume have to do with floating we carried out a bread experiment.

We used two slices of bread. One slice was rolled up tightly which pushed the air out and made it denser. The particles were closer together. The other slice was not rolled up, in fact it was flat, so it still had some air in it.  It was less dense. The two slices of bread weighed the same but one took up more space than the other one and had air in it.

So what happened? 

The rolled up piece of bread sank while the flat piece floated.

We found out that the denser an object is, the more space it needs across the water to make sure that the gravitational and buoyancy forces are equal.  

The material an object is made up of (solid, liquid or gas) can determine how dense it will be. Lets look at a sponge.  If you place a sponge on the surface of the water, it will float because it is made up of solid and gas, which makes it less dense (or lighter) than the water. Eventually it will sink because the gas is replaced with water and it becomes denser or heavier than the water it is floating on. So to understand floating you need to you need to think about buoyancy. To be buoyant you need to be lighter than the water you are floating on according to the amount of space the object takes up on the water.

Mohit knew about the Titanic disaster and wanted to think about what really happened. 

Mohit wrote: 

Sinking and Floating 

While people thought that the ship Titanic was unsinkable, it sank. Have you ever wondered why it sank? I will try to tell you by explaining why some things float while others sink.

First you need to learn about buoyancy force. The buoyancy force of water pushes upward. A ship like Titanic was very heavy but the buoyancy force of the water was stronger and could hold Titanic on the surface, well at least until it got a hole in it.

We carried out an experiment with two balloons to better understand about sinking and floating and this thing called buoyancy. One of the balloons was filled with water and the other was filled with air. We saw the smaller balloon with water in it sink because it was denser than the water underneath it. The large balloon with air in it floated on the surface of the water because it took up more space on the surface and it was much lighter.

The last time I went to the swimming pool, I worked out how these forces helped us to float.  I went to the pool and made a starfish and noticed that my feet were sinking. The muscles in my legs are heavy. I noticed that my lungs helped me float. When your lungs are full of air and you relax you will float a lot easier.  The air in your lungs is light and less dense than your muscle. Water is a liquid and its atoms are closer together than air. The closer the atoms are packed together, the denser something is.

Nishita wrote: 

We found that some of the boats we made had better buoyancy than others. My boat came first because it had a cabin and was balanced properly. I had glued a flat plastic plate made out of polystyrene onto the bottom of the hull. It floated better because it was light and covered more space across the water. The flag made my boat move well when the wind caught it.

My boat was buoyant for two reasons. First the materials I used were lighter. Polystyrene is made with hot air. The air is trapped inside the beads of polystyrene when they are cooled. That's why you use polystyrene boards to help you float in the pool. The other thing that helped my boat to float was the space it took up on the pool. The pressure from the water pushing up against my boat was greater than the pressure of my boat pushing down on the water.

The experiments we carried out taught us about buoyancy and density, and we know what atoms are now!