Transcript Bubbles presentation

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.
Light is a kind of
harmless radiation that
travels as a wave. When
thinking about light
waves it is best to
Bubbles also have some interesting optical properties – they do odd things to light. Light is a kind of harmless
imagine them as
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.
behaving
a bit
like
Where the ripples meet they interfere with each other -- in some places the
waves cancel each other
out, in others
they add together.
ripples in water. If you
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
two
stones
into a
produce a range of colours, called interference colours. The interference drop
colour produced
depends
on the thickness
of the bubble film.
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.