2a Surface tension
What you need:
glas
water
paper clip
What do you have to do?
1 Fill a glass with water.
2 Carefully top the water up until the glass is full. Keep adding water and observe that the water does not overflow but starts building a bulge.
3 Take a paper-clip and carefully slide it onto the water.
4 What happens next? Paper-clip (1) swims/ (2) sinks