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IB Chemistry S1.1 - Into to the Nature of Matter [SL/HL] - Interactive Lecture 2025-2033
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chemistry at its most fundamental level
is the study of matter and when we say
matter we are talking about the material
that makes up the world around us
whether you are looking at another human
an airplane or at the Atlantic Ocean all
of these things are made out of
something they are made out of matter
which is a substance that has mass and
takes up space even if we can't directly
see it like the air around us we can
feel it and breathe it to know it's
there and therefore it has to be made
out of something after extraordinary
scientific research and experimentation
branching all the way back to the early
days of chemistry we acknowledge the
fact that all of the substances around
us and within us are based on building
blocks called atoms we're going to talk
more about atoms in the next video but
for now we just need to know that atoms
are the smallest unit of matter that
retain specific properties that we can
observe in the natural world and if we
take these properties and organize them
we call them elements taking a look at a
periodic table we can see that chemists
have classified provide and organized
many elements that make up our universe
the basic idea of an element is that it
is a pure substance that cannot be
broken down further and still retain its
properties with one atom of an element
being the smallest unit that can hold
those properties let's use carbon and
water as an example to help us
illustrate this carbon is an element
that can exist purely in a few different
ways the lead you use to write in your
school notebook called graphite is made
out of pure carbon if you try to break
the graphite into smaller pieces each
smaller piece would still retain the
same properties and even if you broke
apart each atom within the structure all
of the atoms would still contain the
same properties because they are all
carbon atoms so for this reason we can
say that the graphite within your pencil
is made out of the Pure Element carbon
that cannot be broken down any further
and still retain its properties now we
can contrast this example with something
like water if we were to break water
down we would find that the atoms within
a water molecule have different
properties and as I I'm sure you know
water is made out of two different
elements which are hydrogen and oxygen
breaking apart the atoms of a water
molecule you will find that the
properties between hydrogen and oxygen
are different but the hydrogen atoms and
the oxygen atom cannot be broken down
any further and still retain their
properties so in this scenario we cannot
say that water is an element because it
can be broken down into hydrogen and
oxygen hydrogen and oxygen would be
considered elements as we also see here
on the periodic table each element that
we know of has its own symbol and spot
on the periodic table we learned on the
last slide that elements and their atoms
have their own unique properties but a
cool thing about these atoms of
different elements is that they can
chemically interact with each other to
form larger molecules called compounds
remember that water was made out of
atoms from the elements hydrogen and
oxygen and when these atoms bond
together in a specific ratio of one
oxygen atom to two hydrogen atoms it
creates the compound that we call water
compounds have unique names that are
tied to specific element combinations at
specific ratios so we call a molecule
that has two hydrogen atoms and one
oxygen atom water and a molecule with
two hydrogen atoms and two oxygen atoms
hydrogen peroxide they are both made out
of the same two elements hydrogen and
oxygen but at different ratios one to
two to two to two the ratios that make
up compounds are fixed which means if
they change then the compound itself
changes and this happens all the time
with chemical reactions but more on that
later compounds along with elements are
also classified as pure substances
because they have a uniform composition
two or more elements chemically bound
together form a compound so what happens
if multiple compounds combine we call
this a mixture now we need to be careful
with this term because combining
compounds to make a mixture is different
from combining elements when elements
form a compound they do so with a
chemical change linking the atoms of one
element to the atoms of another other in
a fixed ratio giving the structure new
unique properties if two compounds come
together to form a mixture they do not
chemically change in any way instead
they can simply mix and exist next to
each other with each compound retaining
their original composition and
properties there is no chemical change
that happens a simple example of this
could be sugar water and sugar are both
compounds that have their own unique
properties and when you put them
together they create a mixture of the
two and spread out next to each other
neither of them change at the chemical
level which means that it is easy to
separate them if needed there are only
two types of mixtures that are commonly
seen in the chemistry world called
homogeneous and heterogeneous mixtures a
homogeneous mixture is one that has a
uniform composition meaning everything
is spread out evenly and therefore has
uniform properties salt water is an
example of a homogeneous mixture if you
put salt in water it will dissolve into
sodium and chloride ions and spread out
to be be a uniform composition within
the solution this means that if you were
to take a random sample of the mixture
at any point you would find roughly the
same amount of water sodium and chloride
within the sample this results in the
salt water having the same properties
throughout an example of a heterogeneous
mixture could be a container of muddy
water while there are many compounds
contained within the mud if you let it
sit it will eventually settle at the
bottom of the container so if we were to
take a random sample of this we could
take a collection from the top which
could be mostly water or a collection
from the bottom which would be less
water and more common compounds found
within dirt or soil now the cool thing
about mixtures is that because the
components are not chemically bound to
each other and retain their own
properties they can be separated
relatively easily the common idea behind
separating mixtures is understanding
their properties and using that
information to Aid the separation
filtering is a common way to separate
some mixtures that don't completely
dissolve like some of the particles in
the mud here but that is only one method
other methods can be used like
separating a magnetic substance from a
non-magnetic substance via a magnet
distillation or evaporation of liquids
with different boiling points paper
chromatography crystallization and
others your teacher should go over these
methods in detail with you but for now
always remember that these substances
within mixtures can be separated by
physical means because they are not
chemically bound together and therefore
another important aspect of studying and
understanding matter is learning
information about its state there are
three General states of matter in which
all substances can exist which are solid
liquid and gas take a look around the
world and you can see examples of these
all over the place the water you drink
is a liquid the air you breathe is a gas
and the paper you are currently writing
your notes on is a solid let's stick
with water as our sample substance to
carry through the rest of the slide
solid water or ice can turn into liquid
water through the process of melting and
liquid water can turn into gaseous water
by evaporating we can also go the other
way and say that gaseous water vapor can
condense into liquid water and liquid
water can then freeze into solid ice but
why does this happen what makes the same
liquid water molecules freeze or
solidify that is where the kinetic
molecular theory comes in along with
other things like atmospheric pressure
but we'll talk about that in a later
video the term kinetic describes the
energy an object has due to its motion
and in this case the object is a
molecule which is where we get the
molecular part from the kinetic
molecular theory of matter is a model
that explains the behavior of matter it
states that all matter is made out of
small particles that are in random
motion and have space between them
particles are attracted to each other
and so they tend to pull together and
can move apart only if they have enough
kinetic energy to overcome the force of
attraction so if we have solid ice and
add energy to it by heating it up the
molecules will vibrate and move faster
until some of them start to break off
and are able to freely move around in a
liquid state and then we can continue to
add energy until those liquid water
molecules move so much that they can
break off into a gaseous State the term
endothermic describes a change of state
from more compact to less compact
because energy is taken up for the
physical change to take place and
exothermic describes when energy is
released or taken away from the
substance to cause the state change two
other important state changes to know
about are sublimation and deposition
sublimation occurs when a solid state
changes directly into a gas and
deposition occurs when a gas State
changes directly into a solid both
processes skip the liquid phase and
therefore have a larger EXO and
endothermic swing in energy compared to
just condensing or melting we have
talked a lot about energy heat and
temperature but have yet to put a solid
definition on how we measure it in
chemistry we often measure temperature
which in equations is written as a
capital T using units called Kelvin the
unit for Kelvin is represented with a
capital K and describes the average
kinetic energy of particles this is one
of seven base units of the International
System of Units abbreviated s i that are
wide accepted and used by scientists all
over the world Kelvin measures the
temperature of a substance on an
absolute scale meaning there are only
positive measurements within the system
and the lowest the scale can go is zero
this differs from using the Celsius
scale because temperature and Celsius
can go into the negatives so what does
this actually mean with a Kelvin
temperature of zero which we call
absolute zero means that there is
absolutely no kinetic energy between the
particles being measured meaning that
there is no movement at all between the
particles and therefore has no
collisions and no heat this is the
absolute coldest measurement that
particles can take completely void of
all heat and movement contrast that to
zero degrees Celsius which is the
temperature at which liquid water
freezes into ice we would say that this
is cold but the molecules in the ice
still contain kinetic energy and are
moving and vibrating next to each other
in the solid state and this goes for all
other solids as well there is always a
bit of movement between particles within
a solid state scientists have come close
to reaching absolute zero but have never
actually achieved it because the massive
amount of energy needed to be removed to
eliminate all heat from an object When
comparing the Kelvin scale to the
Centigrade scale they increase by a one
to one equivalent meaning that a
temperature change of one Kelvin is
equal to a temperature change of 1
degree celsius the difference again is
the scale and to convert between the two
we can use the conversion of zero
degrees Celsius is equal to
273.15 Kelvin so we can calculate that
water boils at 100 degrees Celsius which
is 373.5 Kelvin and absolute zero would
be written as zero Kelvin or negative
273.15 Celsius make sure to know how to
convert between the two by either adding
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