Water on it’s own, forms a tight, sticky surface, known as surface tension. That is why this pond skater can walk on water, it is not heavy enough to break the surface tension.

Because of surface tension when you measure with a measuring cylinder the liquid forms a curve known as a meniscus. To read the measuring cylinder correctly you must read it from the same height.

When we add detergent to water, we lower the surface tension making it stretchy. To make the bubbles last longer we will add some sugar. This stops the water evaporating and so the bubbles last. Evaporation: This is when a liquid (e.g. the water in the bubble mixture) changes to a gas (e.g. water vapour).

Our bubble recipe Measure out half a litre (500ml) of water. Add 50ml of detergent. Add a pinch of sugar Mix carefully

Look at the lights through your bubbles what do you see?

Amaze your friends by being able to poke your finger through the bubble sheet without popping the bubble. Dip your finger into the bubble mixture in the washing-up bowl then slowly push it through the bubble sheet. Because your finger is covered in mixture the surface tension (skin) of the bubble is not broken so the bubble sheet does not pop.

Bubbles also have some interesting optical properties – they do odd things to light. Light is a kind of harmless radiation that travels as a wave. When thinking about light waves it is best to imagine them as behaving a bit like ripples in water. If you drop two stones into a pond the ripples spread out from where the stones fell in the water. Where the ripples meet they interfere with each other -- in some places the waves cancel each other out, in others they add together. White light is made from many different colours of light. When white light strikes a bubble it is reflected off both the outer and inner surfaces of the soap film. This creates two sets of light waves that interfere with each other and produce a range of colours, called interference colours. The interference colour produced depends on the thickness of the bubble film. Light is a kind of harmless radiation that travels as a wave. When thinking about light waves it is best to imagine them as behaving a bit like ripples in water. If you drop two stones into a pond the ripples spread out from where the stones fell in the water.

Where the ripples meet they interfere with each other -- in some places the waves cancel each other out, in others they add together.

White light is made from many different colours of light. When white light strikes a bubble it is reflected off both the outer and inner surfaces of the soap film. This creates two sets of light waves that interfere with each other and produce a range of colours, called interference colours. The interference colour produced depends on the thickness of the bubble film.