As we are starting our theme, ‘Unsinkable,’ we carried out an investigation into floating and sinking. Using a plastic bottle, a straw, a paper clip and some blu tac, we made a ‘diver’ and then popped it into a bottle filled with water. By squeezing the bottle, we were demonstrating the property of buoyancy. An object is buoyant in water because it displaces or pushes aside a weight of water greater than the weight of itself. That is how very heavy ships like Titanic managed to float.
When we squeezed our bottle, we increased the pressure of the air bubble in the straw reducing its size. As the bubble got smaller, the ‘diver’ became less buoyant therefore sank. When the pressure was released, the ‘diver’ rose to the top of the bottle.
You could try this at home!
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