Will it sink or will it float? This is the great scientific question of the day as Phil of Science shows us the Cartesian Diver on Hub Lab.

Join Phil Smyth as he mingles magic with science and you can amaze your family and friends with some dark magic this Halloween. 

What are we hoping to do?
1.  Make predictions about what different objects will sink or float.
2.  Learn about pressure, volume, weight, and buoyancy of objects and how these factors may influence floating ability. 


What's going on?
Most children will be able to identify if objects are floating or sinking. If an object is buoyant, it is less dense than the liquid it is floating in or else it will have something attached to it that will help it float, like a life jacket!  An object will sink if it is heavy for its size (paperclip), and float if it is light for its size (log of wood).  Objects are heavier or lighter depending on how dense they are (how much air they have inside them.) 

Squeezing the bottle causes the diver (the eye dropper) to sink because the increased pressure forces water up into the diver, compressing the air at the top of the eye dropper. This increases the mass, and density, of the diver causing it to sink. Releasing the squeeze decreases the pressure on the air at the top of the eyedropper, and the water is forced back out of the diver, lowering its density and allowing it to float back to the top of the bottle.

For the full details and how to run this experiment download the plan below.

Make sure to keep sending your own home experiments to After School Hub: Upload here

Tune in to Phil of Science's Hub Lab on After School Hub at 3pm on RTÉ2.
You can also watch live or catch up on the full show thanks to RTÉ Player.