1.
WATER
1.
Materials change state. This means that in different conditions (such as high
or very high, low or very low temperatures) they change the way they are.
If I
ask you: "Is water the same thing as ice, or is water a different thing to
ice?" I am sure I could get anwers that defend both posibilities.
Your
answer could be:
A-"They
are different, one is a liquid that is not too cold and the other is a hard
solid that is very cold."
B-"They
are the same thing, both are made of the same elements but they are in a
different state."
B would
be more accurate than A, nevertheless A wouldn´t be completely wrong.
What
happens is that in the UNIVERSE we have different temperatures in different
places.
Think
about where you live. In winter temperatures might go below zero ºC, in summer
you might reach 30ºC. Your house can be at a confortable 18-20 ºC. You might
live in the poles (click
me) or in or on the sun (click
me). You might live in Death
Valley (California, USA) where temperatures can reach 57ºC.
These
different temperatures not only make you feel better (or worse) but they also
can change things.
So,
going back to the previous example (WATER), scientists discovered a long, long,
time ago that those two elements that form water, Hidrogen and Oxygen, at
differents temperatures CHANGED STATE!
Look at
the picture above. It shows you the changes that the water (H2O) molecules (groups of
atoms) go through.
If you
look at the pictures above you will see a representation of what the atoms of
water could look like if we saw them.
In one
picture at higher temperature they move and move more so they break their links
and become loose.
In a
second picture the atoms are very still because it's cold. The low temperature
makes the atoms "glue" to each other forming a hard material.
The
third picture shows a situation that is in between the two previous. Not rigid
and not loose. The material has a certain movement, but the atoms are still a
little bit "glued" to each other. This happens at what we could call
more normal temperatures.
The
three states receive the names of solid, liquid and gas. In water we call them
WATER, WATER VAPOUR and ICE.
As a
conclusion, when we change the temperature materials can change their state. So
the same material (water) made of H and O can look very different if it's in a
cold place (ice), in a hot place (water vapour), or at a normal temperature (we
simply call it water).
2.
MORE
CHANGES
Freezing:
When a liquid transforms into a solid, for example water in the freezer
transforms into ice.
Evaporation:
When a liquid transforms into a gas, for example when we have a hot shower or
we boil water.
Boiling:
When a liquid is at very high temperature >100 C and it evaporates fast.
Melting:
When a solid is in a hot place and it transforms into a liquid, for example an
ice-cream under the sun.
Condensation:
When a gas that enters a cold place or touches a cold surface transforms into liquid.
EUREKA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Video ONE
Video TWO
Video THREE
Video FOUR
Video FIVE
3
THE
WATER CYCLE
It is
raining. Have you ever thought of how the water got up to the clouds? Have you
ever thought why it suddenly rains or stops raining? Have you ever thought
about why sometimes it snows? The water cycle explains this. Click me and me.
It is
hot. The sun hits hard on everything. As we have seen, the energy from the sun
changes the state of some materials. So the sun beams hit on the water of the
sea, rivers, lakes and swimming pools. Little amounts of water change into a
gas (water vapour). This gas is made of two elements H and O that float up into
the clouds just like a balloon full of Helium (He). We call this EVAPORATION
When it
reaches the cloud level, as it's cold there, another change of state occurs.
The elements H and O at a cold temperature join together to form water again.
This change from gas to liquid is called CONDENSATION.
As the
liquid is heavy, it is pulled down by gravity, so it rains.
But if
the temperature of the clouds is really, really cold, the liquid formed will go
through another change before it falls: it will freeze! This is what happens
when it snows.
This is
the complete diagram (year 7):
TO
FINISH
Try
these 6 interactive games (thanks Claudia
for the link). Which of these are important for the exam? I´m not telling you.
A. Reversible
and Irreversible Changes and Complete this Quiz
B. Changing
States and Complete this Quiz
C. Material
Properties and Complete this Quiz
D. Rocks
and Soils and Complete this Quiz
E
Solids,
Liquids and Gasses and Complete this Quiz
Enjoy!
