Try this awesome experiment at home! First look at the video below and see if you can predict what science is going on!
HERES A CLUE: you’ll need to think about the term ‘surface tension
A small bowl, a few paper clips, some kitchen roll, some washing up liquid, and a toothpick
- Wash your hands with water before you start this experiment, then cut up some small squares of kitchen roll (3cmx3cm)
- Fill your bowl with water and drop a paper clip into it. Notice that it sinks.
- Now place a small square of kitchen roll onto the surface of the water (3cm x 3cm). It will initially float on the water’s surface.
- Carefully lay a paper clip onto the paper making sure it sits on top.
- Slowly encourage the paper to sink by poking it with a small cocktail stick/toothpick or similar. See how the paper clip remains on the surface appearing to float.
- See if you can repeat stages 2-4 again and count how many paper clips you can get floating at once.
- Then cover the end of your toothpick with washing up liquid, and place it in the water. Watch how the paperclips sink!
Paper clips are made of metal and are therefore are denser than water. This means they will sink.
In the experiment another force is keeping it at the surface; it’s called surface tension. Surface tension exists where the surface of the water meets the air and it’s where the water molecules create a tight arrangement. This tight arrangement of water molecules is like a ‘skin’. This means it can support very light objects that would usually sink such as water insects, leaves and paper clips.
Surface tension can be broken by adding soap molecules to the water. Watch what happens if you add a small drop of washing up liquid to the water.