0:11 thank you
0:13 chemistry at its most fundamental level
0:16 is the study of matter and when we say
0:18 matter we are talking about the material
0:20 that makes up the world around us
0:21 whether you are looking at another human
0:25 an airplane or at the Atlantic Ocean all
0:26 of these things are made out of
0:28 something they are made out of matter
0:30 which is a substance that has mass and
0:33 takes up space even if we can't directly
0:35 see it like the air around us we can
0:36 feel it and breathe it to know it's
0:38 there and therefore it has to be made
0:40 out of something after extraordinary
0:42 scientific research and experimentation
0:44 branching all the way back to the early
0:47 days of chemistry we acknowledge the
0:48 fact that all of the substances around
0:51 us and within us are based on building
0:53 blocks called atoms we're going to talk
0:55 more about atoms in the next video but
0:57 for now we just need to know that atoms
0:59 are the smallest unit of matter that
1:01 retain specific properties that we can
1:03 observe in the natural world and if we
1:06 take these properties and organize them
1:08 we call them elements taking a look at a
1:10 periodic table we can see that chemists
1:12 have classified provide and organized
1:14 many elements that make up our universe
1:17 the basic idea of an element is that it
1:19 is a pure substance that cannot be
1:21 broken down further and still retain its
1:23 properties with one atom of an element
1:25 being the smallest unit that can hold
1:27 those properties let's use carbon and
1:29 water as an example to help us
1:31 illustrate this carbon is an element
1:33 that can exist purely in a few different
1:35 ways the lead you use to write in your
1:38 school notebook called graphite is made
1:39 out of pure carbon if you try to break
1:42 the graphite into smaller pieces each
1:43 smaller piece would still retain the
1:45 same properties and even if you broke
1:48 apart each atom within the structure all
1:49 of the atoms would still contain the
1:51 same properties because they are all
1:53 carbon atoms so for this reason we can
1:55 say that the graphite within your pencil
1:58 is made out of the Pure Element carbon
2:00 that cannot be broken down any further
2:02 and still retain its properties now we
2:04 can contrast this example with something
2:06 like water if we were to break water
2:08 down we would find that the atoms within
2:09 a water molecule have different
2:12 properties and as I I'm sure you know
2:13 water is made out of two different
2:16 elements which are hydrogen and oxygen
2:18 breaking apart the atoms of a water
2:19 molecule you will find that the
2:21 properties between hydrogen and oxygen
2:24 are different but the hydrogen atoms and
2:26 the oxygen atom cannot be broken down
2:28 any further and still retain their
2:30 properties so in this scenario we cannot
2:32 say that water is an element because it
2:34 can be broken down into hydrogen and
2:37 oxygen hydrogen and oxygen would be
2:39 considered elements as we also see here
2:41 on the periodic table each element that
2:43 we know of has its own symbol and spot
2:46 on the periodic table we learned on the
2:48 last slide that elements and their atoms
2:50 have their own unique properties but a
2:51 cool thing about these atoms of
2:53 different elements is that they can
2:55 chemically interact with each other to
2:57 form larger molecules called compounds
2:59 remember that water was made out of
3:01 atoms from the elements hydrogen and
3:04 oxygen and when these atoms bond
3:06 together in a specific ratio of one
3:09 oxygen atom to two hydrogen atoms it
3:11 creates the compound that we call water
3:13 compounds have unique names that are
3:15 tied to specific element combinations at
3:18 specific ratios so we call a molecule
3:20 that has two hydrogen atoms and one
3:22 oxygen atom water and a molecule with
3:25 two hydrogen atoms and two oxygen atoms
3:27 hydrogen peroxide they are both made out
3:30 of the same two elements hydrogen and
3:32 oxygen but at different ratios one to
3:35 two to two to two the ratios that make
3:37 up compounds are fixed which means if
3:39 they change then the compound itself
3:41 changes and this happens all the time
3:43 with chemical reactions but more on that
3:46 later compounds along with elements are
3:48 also classified as pure substances
3:49 because they have a uniform composition
3:52 two or more elements chemically bound
3:54 together form a compound so what happens
3:56 if multiple compounds combine we call
3:59 this a mixture now we need to be careful
4:00 with this term because combining
4:02 compounds to make a mixture is different
4:05 from combining elements when elements
4:07 form a compound they do so with a
4:09 chemical change linking the atoms of one
4:11 element to the atoms of another other in
4:14 a fixed ratio giving the structure new
4:16 unique properties if two compounds come
4:18 together to form a mixture they do not
4:21 chemically change in any way instead
4:23 they can simply mix and exist next to
4:25 each other with each compound retaining
4:27 their original composition and
4:29 properties there is no chemical change
4:31 that happens a simple example of this
4:34 could be sugar water and sugar are both
4:36 compounds that have their own unique
4:37 properties and when you put them
4:39 together they create a mixture of the
4:41 two and spread out next to each other
4:43 neither of them change at the chemical
4:45 level which means that it is easy to
4:47 separate them if needed there are only
4:49 two types of mixtures that are commonly
4:51 seen in the chemistry world called
4:54 homogeneous and heterogeneous mixtures a
4:57 homogeneous mixture is one that has a
4:59 uniform composition meaning everything
5:01 is spread out evenly and therefore has
5:04 uniform properties salt water is an
5:06 example of a homogeneous mixture if you
5:08 put salt in water it will dissolve into
5:10 sodium and chloride ions and spread out
5:13 to be be a uniform composition within
5:15 the solution this means that if you were
5:17 to take a random sample of the mixture
5:19 at any point you would find roughly the
5:21 same amount of water sodium and chloride
5:24 within the sample this results in the
5:25 salt water having the same properties
5:28 throughout an example of a heterogeneous
5:30 mixture could be a container of muddy
5:32 water while there are many compounds
5:34 contained within the mud if you let it
5:36 sit it will eventually settle at the
5:38 bottom of the container so if we were to
5:40 take a random sample of this we could
5:42 take a collection from the top which
5:44 could be mostly water or a collection
5:46 from the bottom which would be less
5:48 water and more common compounds found
5:50 within dirt or soil now the cool thing
5:51 about mixtures is that because the
5:53 components are not chemically bound to
5:55 each other and retain their own
5:57 properties they can be separated
6:00 relatively easily the common idea behind
6:01 separating mixtures is understanding
6:03 their properties and using that
6:05 information to Aid the separation
6:07 filtering is a common way to separate
6:09 some mixtures that don't completely
6:10 dissolve like some of the particles in
6:13 the mud here but that is only one method
6:14 other methods can be used like
6:17 separating a magnetic substance from a
6:19 non-magnetic substance via a magnet
6:21 distillation or evaporation of liquids
6:23 with different boiling points paper
6:26 chromatography crystallization and
6:28 others your teacher should go over these
6:30 methods in detail with you but for now
6:32 always remember that these substances
6:34 within mixtures can be separated by
6:36 physical means because they are not
6:38 chemically bound together and therefore
6:52 another important aspect of studying and
6:54 understanding matter is learning
6:57 information about its state there are
6:59 three General states of matter in which
7:01 all substances can exist which are solid
7:04 liquid and gas take a look around the
7:06 world and you can see examples of these
7:08 all over the place the water you drink
7:10 is a liquid the air you breathe is a gas
7:13 and the paper you are currently writing
7:15 your notes on is a solid let's stick
7:17 with water as our sample substance to
7:18 carry through the rest of the slide
7:22 solid water or ice can turn into liquid
7:24 water through the process of melting and
7:27 liquid water can turn into gaseous water
7:30 by evaporating we can also go the other
7:33 way and say that gaseous water vapor can
7:35 condense into liquid water and liquid
7:38 water can then freeze into solid ice but
7:40 why does this happen what makes the same
7:43 liquid water molecules freeze or
7:45 solidify that is where the kinetic
7:47 molecular theory comes in along with
7:49 other things like atmospheric pressure
7:50 but we'll talk about that in a later
7:52 video the term kinetic describes the
7:55 energy an object has due to its motion
7:57 and in this case the object is a
7:58 molecule which is where we get the
8:00 molecular part from the kinetic
8:02 molecular theory of matter is a model
8:05 that explains the behavior of matter it
8:07 states that all matter is made out of
8:09 small particles that are in random
8:11 motion and have space between them
8:13 particles are attracted to each other
8:15 and so they tend to pull together and
8:17 can move apart only if they have enough
8:19 kinetic energy to overcome the force of
8:22 attraction so if we have solid ice and
8:24 add energy to it by heating it up the
8:26 molecules will vibrate and move faster
8:28 until some of them start to break off
8:30 and are able to freely move around in a
8:33 liquid state and then we can continue to
8:34 add energy until those liquid water
8:37 molecules move so much that they can
8:39 break off into a gaseous State the term
8:41 endothermic describes a change of state
8:43 from more compact to less compact
8:45 because energy is taken up for the
8:47 physical change to take place and
8:49 exothermic describes when energy is
8:51 released or taken away from the
8:53 substance to cause the state change two
8:55 other important state changes to know
8:57 about are sublimation and deposition
9:00 sublimation occurs when a solid state
9:03 changes directly into a gas and
9:05 deposition occurs when a gas State
9:07 changes directly into a solid both
9:09 processes skip the liquid phase and
9:11 therefore have a larger EXO and
9:13 endothermic swing in energy compared to
9:16 just condensing or melting we have
9:18 talked a lot about energy heat and
9:20 temperature but have yet to put a solid
9:22 definition on how we measure it in
9:24 chemistry we often measure temperature
9:26 which in equations is written as a
9:29 capital T using units called Kelvin the
9:31 unit for Kelvin is represented with a
9:33 capital K and describes the average
9:35 kinetic energy of particles this is one
9:37 of seven base units of the International
9:40 System of Units abbreviated s i that are
9:43 wide accepted and used by scientists all
9:45 over the world Kelvin measures the
9:46 temperature of a substance on an
9:48 absolute scale meaning there are only
9:50 positive measurements within the system
9:53 and the lowest the scale can go is zero
9:54 this differs from using the Celsius
9:57 scale because temperature and Celsius
9:59 can go into the negatives so what does
10:01 this actually mean with a Kelvin
10:02 temperature of zero which we call
10:05 absolute zero means that there is
10:07 absolutely no kinetic energy between the
10:09 particles being measured meaning that
10:11 there is no movement at all between the
10:13 particles and therefore has no
10:16 collisions and no heat this is the
10:17 absolute coldest measurement that
10:20 particles can take completely void of
10:22 all heat and movement contrast that to
10:24 zero degrees Celsius which is the
10:25 temperature at which liquid water
10:28 freezes into ice we would say that this
10:30 is cold but the molecules in the ice
10:31 still contain kinetic energy and are
10:33 moving and vibrating next to each other
10:35 in the solid state and this goes for all
10:38 other solids as well there is always a
10:39 bit of movement between particles within
10:42 a solid state scientists have come close
10:43 to reaching absolute zero but have never
10:45 actually achieved it because the massive
10:48 amount of energy needed to be removed to
10:50 eliminate all heat from an object When
10:52 comparing the Kelvin scale to the
10:54 Centigrade scale they increase by a one
10:56 to one equivalent meaning that a
10:57 temperature change of one Kelvin is
10:59 equal to a temperature change of 1
11:02 degree celsius the difference again is
11:04 the scale and to convert between the two
11:06 we can use the conversion of zero
11:08 degrees Celsius is equal to
11:11 273.15 Kelvin so we can calculate that
11:14 water boils at 100 degrees Celsius which
11:18 is 373.5 Kelvin and absolute zero would
11:21 be written as zero Kelvin or negative
11:24 273.15 Celsius make sure to know how to
11:26 convert between the two by either adding
11:56 [Music] foreign
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