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TGR1:
What speeds up evaporation?
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The
topic of evaporation was introduced in G1. If you want to
review that section with your class before going on, return
to the main content and use the drop -down menu at the top
right to go straight to the start of G1. You can use the same
method to get back to R1 quickly.
Notes on ‘Think for Yourself’ questions
Why does a bigger surface area increase the rate of evaporation?
The particles leave from the surface.
With a bigger surface area, more particles can leave at the
same time.
Why does water evaporate faster in a warmer room?
The water is warmer and the air is
warmer. Only high energy water particles can leave on their
own, and the
warmer the water, the more high energy water particles there
are. Only high energy air particles can knock out
medium and low energy water particles: the warmer the air,
the more high energy air particles there are.
Look at the animation again. Notice that some water particles
are returning. If 50 water particles leave and 20
water particles return every second, what is the overall rate
of evaporation?
30 particles per second (These
numbers aren’t ‘real’: they just illustrate
the point).
How would a fan affect the rate at which water particles leave
the surface?
The rate would not change because
the number of high energy water particles and high energy
air particles would
not be changed (because a fan does not warm up the room).
So how can a fan speed up the rate of evaporation?
It creates a breeze, which reduces
the number of water particles which can return. The bigger
the difference in
numbers leaving and returning, the faster the rate of evaporation.
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Science Enhancement Programme CD-ROM 2005 |
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user
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