Changing States of Matter

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Changing States of Matter
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PART ONE
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What states of matter do you know?
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We are going to analyse just three of them, the
main ones Solid Liquid Gas
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Now, name at least two examples for each of the
three states.
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Materials can be changed from one state to
another by adding ...

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And what's the easiest energy around?
energy
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Probably heat!
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But matter changes if you take away heat from it,
too.
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Adding energy is HEATING Taking away energy is
COOLING
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Heating Heat can change solids into liquids or
gases. Most solids melt into liquid when they
are heated. A liquid evaporates into a gas
when it is heated. Let's see what happens to
water.
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If ice (solid) is heated, it changes to water
(liquid). This change is called
melting. Water (liquid) can change to water
vapour (gas). This is called evaporation. If
water (liquid) is heated until it boils, it
changes to water vapour (gas) very quickly.
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Cooling Cold can change gases and liquids.
Gases may change to liquids. This change is
called condensing. Liquids may change to
solids. This change is called freezing.

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Cooling If water vapour (gas) is cooled, it
changes to water (liquid). This change is called
condensing. If water (liquid) is cooled, it
changes to ice (solid). This change is called
freezing.
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Different solids melt at different temperatures,
some high, some low. These are called their...
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melting points.
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Different liquids freeze at different
temperatures.
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Scientists use something called a freezing point
to measure when that liquid turns into a solid
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Finally, different gases turn to liquids at
different condensation points.
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Sublimation This is when a solid, on heating,
directly changes into a gas without melting, AND
the gas on cooling re-forms a solid directly
without condensing to a liquid. They usually
involve just a physical change BUT its not always
that simple!
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Chemical vs. Physical Changes It is important to
understand the difference between chemical and
physical changes. The two types are based on
studying chemical reactions and states of
matter. Physical changes are about energy and
states of matter. Chemical changes happen on a
molecular level.
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When you melt an ice cube you have forced a
physical change (adding energy). That example
caused a change in the state of matter. You can
cause physical changes with forces like motion,
temperature, pressure.
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Now, we know matter can change from one state to
another. But what happens inside matter when
such changers occur?
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Pressure
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Let's start it all over agian... What is a
solid? Solids are usually hard because their
molecules have been packed together. The closer
your molecules are, the harder you are. Solids
also can hold their own shape. A rock will
always look like a rock unless something happens
to it.
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Even when you grind up a solid into a powder, you
will see little tiny pieces of that solid under a
microscope. Liquids will move and fill up any
container. Solids like their shape.
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In the same way that a solid holds its shape, the
atoms inside of a solid are not allowed to
move around too much. This is one of the
physical characteristics of solids.
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Atoms and molecules in liquids and gases are
bouncing and floating around, free to move where
they want. The molecules in a solid are stuck.
The atoms still spin and the electrons fly
around, but the entire atom will not change
position.
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The second state of matter we will discuss is a
liquid. Solids are hard things you can hold.
Gases are floating around you and in bubbles.
What is a liquid? Water is a liquid.
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Liquids are an in-between state of matter. They
can be found in between the solid and gas states.
They do not have to be made up of the same
compounds. If you have a variety of materials in
a liquid, it is called a solution.
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One characteristic of a liquid is that it will
fill up the shape of a container. It fills the
bottom first because of gravity. The top part of
a liquid will usually have a flat surface. That
flat surface is because of gravity too.
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A special force keeps liquids together. Solids
are stuck together and you have to force them
apart. Gases bounce everywhere and they try to
spread themselves out. Liquids actually want to
stick together.
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There will always be the occasional evaporation
where extra energy gets a molecule excited and
the molecule leaves the system. Overall,
liquids have cohesive (sticky) forces at work
that hold the molecules together.
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A special force keeps liquids together. Solids
are stuck together and you have to force them
apart. Gases bounce everywhere and they try to
spread themselves out.
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Liquids actually want to stick together. There
will always be the occasional evaporation where
extra energy gets a molecule excited and the
molecule leaves the system. Overall, liquids
have cohesive (sticky) forces at work that hold
the molecules together.
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PART TWO AFTER THE SIMULATION
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All matter is made up of tiny particles called
atoms. These particles are always moving and
are attracted to one another. A material's state
of matter is determined by the movement of the
particles. The more energy they have, the
further apart they want to get from each other.
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Solids A solid is the state of matter that has
the least amount of energy. It has a definite
shape and volume. The particles of a solid are
packed close together. The particles of a solid
are moving, vibrating back and forth, but they
don't have enough energy to break away from one
another.
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A liquid is matter that has a definite volume but
no definite shape. A liquid takes the shape of
its container but keeps the same volume. The
particles in a liquid move more freely than those
in a solid, but do not have enough energy to move
apart from one another
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Gas is matter that does not have a definite shape
or volume. The particles in a gas are far apart
and move quickly in all directions. A gas can
expand or be compressed much easier than a liquid
and a solid. Think of a balloon filled with
air. What happens if you squeeze the air into a
smaller part of the balloon? The gas particles
or random groups of atoms, get closer together.
Most gases are invisible, such as the air you
breathe.
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Plasma, the 4th state of matter, only happens at
very high temperatures. Plasma is a lot like a
gas, except for the fact that electrons get
stripped from neutral atoms of the element. It
does not occur naturally on Earth, but can be
found in neon signs, fluorescent lights, plasma
tv's, and lightening. Most of the visible
universe is in the state of plasma, such as
stars, which are big balls of gases (hydrogen
helium) at really high temperatures.
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What happens when I add energy to a solid?
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Physical Change A Physical Change is a change in
the way an object looks, but not in what the
object is made of. Changing of state, such as a
pond freezing in the winter is an example of a
physical change. The appearance of the pond has
changed, but the composition of the water has not
changed, it is still made of hydrogen and oxygen.
Changing shape is also a physical change. Like
crumpling paper, cutting a banana, or slicing an
apple are all examples. When you cut, tear,
grind, or bend matter, you cause a physical
change.
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Dissolving sugar in iced tea is a physical
change, which is often misconceived as a chemical
change. Salt in water is also another example.
When you not sure whether it is physical or
chemical you can always ask yourself did the
substance change composition after the change.
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Chemical Change In a Chemical Change substances
are changed into different substances. Fireworks
are a prime example of a chemical change. The
explosions and colors are evidence of changes in
compostion. Chemical changes are often hard to
spot, but there are some signs to look when
determining if it is a change in
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compostion. The easiest to spot is a color
change. Have you ever seen an apple slice turn
brown? A chemical change occurs when an apple
reacts with oxygen in the air. This occurs with
other fruits as well. Leaves changing colors in
the fall is also a good example. Energy is
another sign of a chemical change. Many
substances must absorb energy to have a chemcial
change. For example, what do you add to pancake
batter to make it turn into a pancake? Energy in
the form of heat is added. The energy is absorbed
by the pancake batter as it undergoes a chemcial
change and a solid pancake is the result.
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Conservation of Mass The Law of Conservation of
Mass state that the total mass of matter is the
same before and after physical or chemical
changes. So, matter cannot be created or
destroyed.