presents
Quite
Interesting
Science
This week:
Snow and ice
1 Is it possible to walk across the
English Channel?
1
2
It would be – if it was frozen. But will
this ever happen?
We all know pure water freezes at 0 ºC.
But salty water doesn’t freeze until it
gets even colder.
There is a lot of water in the channel.
It would take ages for all the particles
to get into a regular pattern and form
ice. So it would need to be very cold
for a very long time to freeze the
channel.
2 Why spread grit on icy roads?
1
2
Grit is actually rock salt - a mixture of
crushed rock and salt. It’s what they
dig out of salt mines. So why use salt?
Salt can stop water freezing.
When the salt dissolves, it lowers
water’s freezing point. So ice will
only form at temperatures much
lower than 0°C.
3 It's 4oC today, so how come
the snow hasn’t melted?
Melting takes time. It’s the same
with ice-cream. Why?
The ice particles have to absorb
energy to overcome the attractive
forces holding them together.
Supplying enough energy
takes time.
4 The road is ice-free…
…but in 10s the driver
will skid over the side
of a bridge! Why?
Bridges get icy (and slippery) before
the roads on land. Why is this?
Bridges contain a lot of metal, so
they cool down quicker than roads.
Bridges lose heat fast because
metals are such good conductors.
5 When can water pack a
bigger punch than a boxer?
Water forms ice when it freezes.
But why is ice so hard?
Look at these icicles,
you wouldn’t want one
falling on your head!
Icicles are hard because
strong forces hold their
particles together.
6 Why might cold spells give
joy to children at Christmas?
Sprouts contain water, so what happens
when the temperature drops?
The ice in frozen sprouts is brittle.
It shatters in the machines that
harvest them, which breaks
the sprouts up.
Frozen sprouts can be harvested by
hand, but this is slow and expensive.
So lots of children will have to go
without sprouts on Christmas Day.
7 Why doesn’t this frog need
to stay warm?
If you stayed out in freezing
weather for too long, you would die.
But wood frogs can survive. How?
They fill their cells with sugar. This
acts like antifreeze to stop them
freezing solid.
The frog’s antifreeze stops ice
forming the same way salt stops it
forming on roads.
8 You throw water up - snow
comes down. How come?
The air has to be cold – very cold.
In Siberia it is –40 ºC. What
happens to the water in the air?
It freezes instantly as water
particles lose energy and fit
together to form crystals.
Throwing it up helps by forming
droplets. Their large surface area,
makes them lose energy faster.
9 Why is water strange?
solid water
liquid water
If this was any other substance,
the solid state would sink.
So why do icebergs float?
When most substances freeze,
their particles get closer together,
so they get denser.
Water is strange because the particles
in ice crystals are more spread out,
which makes it less dense than water.
10 Santa has a new sledge.
It’s made of plastic. Is this a
good choice of material?
1
2
Plastic is lightweight so it’s easier for his
reindeer to pull, but will it survive the
freezing temperatures on Christmas Eve?
Maybe not! Plastic particles are like strands
of cooked spaghetti. They slip and slide
over each other to make a soft, flexible
material.
But when the temperature drops the
particles lose energy and stick together.
The plastic goes rigid and brittle like glass.
Any small pushing force could make the
sledge shatter.
THE END
No
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answer
Yes. Use the
Channel Tunnel
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answer
Grit is dark. So it
absorbs more
sunlight and melts
snow.
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answer
Grit increases
friction so cars
don’t slide.
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answer
Snow melts at a
higher temperature
than ice.
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answer
Bridges aren’t
gritted.
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answer
Its too cold for
brussel sprouts
to grow.
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answer
It can’t.
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answer
It can’t feel the
cold.
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answer
It’s not.
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answer
Yes
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answer
No
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answer