Unit 1 Topic 1 Packet
Summary
TLDRThis lesson provides an introduction to the structure of water and hydrogen bonding, starting with a chemistry review of matter, elements, compounds, and the periodic table. It covers atomic structure, the Bohr and Lewis dot models, and the types of chemical bonds, including covalent, ionic, and hydrogen bonds. The video emphasizes water's unique properties such as cohesion, adhesion, high specific heat, evaporative cooling, and its role as a versatile solvent. Additionally, the lesson highlights how water's structure supports life, especially in plants and marine environments.
Takeaways
- 💧 Matter includes anything that takes up space and has mass, such as liquids, solids, and gases.
- 🧪 An element cannot be broken down into another substance by chemical reactions, while a compound consists of two or more elements combined in a fixed ratio.
- ⚛️ Essential elements like carbon, hydrogen, oxygen, phosphorus, and nitrogen (CHOPIN) make up 96% of living matter, while trace elements are required in small amounts.
- 🔢 The periodic table is organized by groups (vertical columns) that have the same number of valence electrons and periods (horizontal rows) with the same number of electron shells.
- 🔬 The Bohr model shows electrons orbiting the nucleus in energy levels, while the Lewis dot model focuses only on valence electrons.
- 🔗 Chemical bonds form based on the octet rule, where elements gain, lose, or share electrons to complete their valence shells, leading to stability.
- 🧲 Covalent bonds involve the sharing of electrons between atoms, which can be polar (unequal sharing) or non-polar (equal sharing).
- ⚡ Ionic bonds are formed by the transfer of electrons between oppositely charged ions, typically between metals and non-metals.
- 🌊 Hydrogen bonds are intermolecular attractions, not actual bonds, occurring between polar covalent molecules like water.
- 🌡️ Water has unique properties due to hydrogen bonding, including cohesion, adhesion, capillary action, temperature control, and solvent capabilities.
Q & A
What is the difference between matter, elements, and compounds?
-Matter is anything that takes up space and has mass, such as liquids, solids, gases, or living organisms. An element is a substance that cannot be broken down into simpler substances by chemical reactions, while a compound consists of two or more elements combined in a fixed ratio, like water (H2O) or sodium chloride (NaCl).
What are essential elements, and why are they important?
-Essential elements, such as carbon, hydrogen, oxygen, phosphorus, and nitrogen (abbreviated as 'CHOPN'), make up 96% of living matter. These elements are crucial for various biological processes, like forming biomolecules (proteins, lipids, DNA).
What are trace elements, and what role do they play in organisms?
-Trace elements are required by organisms in very small quantities. Examples include iron (important for oxygen transport in blood) and iodine (needed for thyroid hormone production). Despite their small presence, they are vital for maintaining healthy biological functions.
How do you interpret the atomic number and atomic mass of an element?
-The atomic number represents the number of protons in an atom, while the atomic mass is the combined total of protons and neutrons, averaged across all isotopes of the element.
What is the difference between covalent, polar covalent, and ionic bonds?
-Covalent bonds involve the sharing of electrons between two non-metals. Polar covalent bonds are a type of covalent bond where electrons are shared unequally, leading to partial charges (e.g., in water). Ionic bonds occur when one atom transfers electrons to another, typically between a metal and non-metal, resulting in oppositely charged ions (e.g., sodium chloride).
What is the octet rule, and how does it relate to chemical bonding?
-The octet rule states that atoms tend to gain, lose, or share electrons to complete their valence shell with eight electrons, resembling the stable configuration of noble gases. This rule drives the formation of chemical bonds between atoms.
What are hydrogen bonds, and how do they differ from other types of bonds?
-Hydrogen bonds are weak attractions between a partially positive hydrogen atom in one polar covalent molecule and an electronegative atom (like oxygen or nitrogen) in another polar covalent molecule. Unlike covalent and ionic bonds, hydrogen bonds are intermolecular attractions, not true bonds.
Why is water considered a polar molecule, and how does this contribute to hydrogen bonding?
-Water is polar because of the unequal sharing of electrons between oxygen and hydrogen atoms, with oxygen having a partial negative charge and hydrogen having a partial positive charge. This polarity allows water molecules to form hydrogen bonds with each other, contributing to water's unique properties.
What are cohesion and adhesion, and how do they contribute to water's movement in plants?
-Cohesion refers to water molecules sticking to each other due to hydrogen bonding, while adhesion refers to water molecules sticking to other surfaces, like plant cell walls. Together, these properties facilitate capillary action, allowing water to move against gravity in plants from roots to leaves.
How do hydrogen bonds contribute to water's high specific heat and evaporative cooling?
-Hydrogen bonds in water require heat to be absorbed to break and release heat when they form, stabilizing water's temperature (high specific heat). During evaporative cooling, water molecules with the highest kinetic energy leave as gas, cooling the surface they evaporate from, like during sweating or transpiration in plants.
Outlines
🔬 Introduction to Chemistry: Matter, Elements, and Compounds
The first paragraph introduces the concepts of matter, elements, and compounds. Matter is defined as anything that takes up space and has mass. Elements are substances that cannot be broken down by chemical reactions, while compounds consist of two or more elements in a fixed ratio, like water (H2O) and sodium chloride (NaCl). Essential elements such as carbon, hydrogen, oxygen, phosphorus, and nitrogen (CHOPN) make up 96% of living matter, while trace elements are needed in small quantities. The paragraph ends with a quick exercise, asking learners to review the role of essential and trace elements in the body.
🧬 Reading the Periodic Table: Groups, Periods, and Atomic Structure
This section explains how to read the periodic table. The atomic number represents the number of protons, while the atomic mass is the number of protons plus neutrons. Elements in the same group (vertical column) have the same number of valence electrons, important for chemical bonding. The horizontal rows, or periods, represent the number of electron shells. Valence electrons are explained in detail, and the paragraph reviews how elements are grouped in the periodic table based on these properties.
🔄 Bohr Model and Lewis Dot Model
This part introduces the Bohr model and Lewis dot model. The Bohr model shows electrons orbiting the nucleus in defined energy levels (shells), with specific electron capacities per shell. An example using lithium is provided, demonstrating its electron configuration. The Lewis dot model simplifies the Bohr model by showing only valence electrons around the element symbol. Both models are important for understanding electron arrangements and bonding.
💡 Chemical Bonding: Octet Rule and Covalent Bonds
The paragraph explains why elements form bonds based on the octet rule, which states that atoms will gain, lose, or share electrons to fill their valence shell. Covalent bonds are introduced as bonds formed by sharing electrons between two non-metals. These can be single, double, or triple bonds, depending on the number of shared electron pairs. The paragraph distinguishes between non-polar covalent bonds, where electrons are shared equally, and polar covalent bonds, where electrons are unequally shared, like in water (H2O).
⚛️ Ionic and Hydrogen Bonds
Ionic bonds are introduced as bonds formed through the transfer of electrons between atoms, usually between metals and non-metals, leading to the creation of oppositely charged ions (cations and anions). An example of sodium chloride (NaCl) demonstrates this process. The paragraph also explains hydrogen bonds as attractions between partially positive hydrogen atoms and electronegative atoms (like oxygen or nitrogen) in polar molecules, clarifying that these are attractions rather than actual bonds.
💧 Hydrogen Bonding in Water and Its Properties
This section dives deeper into hydrogen bonding in water molecules. It explains how hydrogen bonds cause water molecules to be attracted to each other, contributing to water's unique properties. Water molecules are constantly moving, with hydrogen bonds forming and breaking frequently, which gives water its structured nature. The paragraph emphasizes that hydrogen bonds occur between different water molecules and are responsible for water's liquid structure.
🌊 Water Properties: Polarity and Cohesion
The paragraph outlines key properties of water, starting with polarity. Water is a polar molecule, meaning it has unequal sharing of electrons, leading to hydrogen bonding. Cohesion is the attraction between water molecules, which is vital for the movement of water and nutrients in plants. The hydrogen bonds between water molecules are responsible for cohesion and surface tension, allowing water to resist external forces.
🪶 Adhesion and Capillary Action
This section discusses adhesion, the attraction between water molecules and different substances. Adhesion, along with cohesion, enables water to travel upwards through plant tissue, specifically the xylem. This movement is known as capillary action, a process where water climbs against gravity due to a combination of cohesion, adhesion, and surface tension, which is critical for nutrient and water transport in plants.
🔥 Water’s Role in Temperature Regulation
Water has a high specific heat, meaning it can absorb and release large amounts of heat without drastically changing temperature. This property helps regulate air and ocean temperatures and maintain stable conditions for marine life. Additionally, evaporative cooling—when water molecules with the highest kinetic energy leave as gas—helps prevent overheating in organisms and plants through processes like sweating and transpiration.
❄️ Ice Formation and Density
The paragraph explains how water's density changes when it freezes. As water cools, hydrogen bonds slow down, locking water molecules into a crystalline structure, which causes ice to expand and become less dense than liquid water. This property allows ice to float, creating an insulating layer that enables marine life to survive in freezing environments.
💧 Water as a Universal Solvent
The final paragraph highlights water's ability to dissolve many substances due to its polar nature, earning it the title of 'universal solvent.' Water molecules are attracted to ions and other polar molecules, forming hydrogen bonds that break apart solutes like sugars and salts. The process of dissolving ionic compounds is demonstrated using sodium chloride as an example, showing how water molecules separate ions into solution.
Mindmap
Keywords
💡Matter
💡Element
💡Compound
💡Essential Elements
💡Atomic Structure
💡Bohr Model
💡Covalent Bonds
💡Ionic Bonds
💡Hydrogen Bonding
💡Properties of Water
Highlights
Introduction to the structure of water and hydrogen bonding.
Review of chemistry concepts: matter, elements, and compounds.
Essential elements for life: Carbon, Hydrogen, Oxygen, Phosphorus, Nitrogen (CHOPN), making up 96% of living matter.
Explanation of trace elements and their importance in small quantities for organisms.
Overview of the periodic table: atomic number, atomic mass, groups, and periods.
Bohr model of an atom: electrons orbit the nucleus in specific shells, with examples like lithium.
Lewis dot model: Simplified Bohr model focusing on valence electrons around the element symbol.
Formation of chemical bonds based on the octet rule: elements gain, lose, or share electrons to complete their valence shells.
Types of bonds: Covalent (polar and non-polar), Ionic, and Hydrogen bonds.
Explanation of electronegativity and its role in bond formation, with fluorine being the most electronegative element.
Hydrogen bonding between water molecules and its role in water's unique properties.
Cohesion and adhesion in water, allowing for capillary action in plants.
Temperature control in water: high specific heat helps moderate air temperature and stabilizes marine life environments.
Ice density: water becomes less dense when frozen, forming a crystalline structure, allowing marine life to survive under ice.
Water as a universal solvent: able to dissolve ions and polar molecules due to hydrogen bonds.
Transcripts
welcome to unit one topic one today
we're going to be discussing the
structure of water and hydrogen bonding
but let's go ahead and get started first
with a quick review on chemistry
and let's start with what's the
difference between matter elements and
compounds so firstly matter remember
this is anything that takes up space and
has
mass so liquid solids gases you and i
rocks metals right all that that's all
matter
an element is something that cannot be
broken down
into another substance by chemical
reactions so think the periodic table of
elements right we have
lots of elements that occur in nature
and they can't be broken down into
another substance
compounds on the other hand are a
substance consisting of two or more
elements combined in a fixed ratio so
like
water h2o sodium chloride nacl
that's an example of a compound now
of all of our elements we have certain
ones that are considered essential
these are carbon hydrogen oxygen
phosphorus and nitrogen
or you can say chop it these make up 96
of living matter and then off of
essential elements we have things called
trace elements and these
are required by organisms but in very
small
quantities
so let's go ahead and take a minute i
want you to look up what are some
essential elements
why are they essential we went through
choppin so why don't you take
a second look at what each of those or
what role each of those plays in the
body
and then look up trace elements and try
to find some trace elements and what
what are
their roles in the body as well maybe
one to two trace elements
all right let's do a quick chemistry or
let's continue with our quick chemistry
review
i'm looking at this we this is our
element symbol here then we have the
atomic number
and then our atomic mass this is the
number of protons
plus neutrons averaged over all of our
isotopes so
looking at each element on the periodic
table
that's how to read this now going off of
this let's look at our groups and
periods so
groups elements in the same vertical
column
or in the same group have the same
number of valence electrons
now for the ap biology exam you only
need to know groups 1
2 and then we skip over 13 through 18.
and remember valence electrons this has
one two
and then we go to 13 for three four five
six seven eight and these are
noble gases here in group 18.
okay and then period this is going to be
the horizontal row um and anything in a
horizontal row will have the same number
of electron
shells okay what else do you remember
about the periodic table go and go ahead
take a minute think about
what you've learned in a previous
bio or chem class what do you remember
about the periodic table
okay let's go ahead and look at the bohr
model bohr models show electrons
orbiting the nucleus of an atom
and electrons will be placed on shells
around the nucleus
and remember each shell is a different
energy level and can hold up to a
certain number of electrons
first shell can hold two electrons
second shell
eight and third shell is 18 but for the
ap bio exam
we're not going to look at anything in
the third shell that can hold
more than eight electrons
all right so let's go ahead and look at
an example of a bohr model using
lithium so here's lithium on the
periodic table we can see it's in group
one period two um period two would mean
it has two
shells then group one means we have one
valence electron
i has three protons three electrons
um so how would we draw this well we
would put these shells or two shells
around the nucleus
the first shell remember can hold up to
two second shell can hold up to eight
but we would only have one left over so
we put that uh
final one on the second shell or our
valence electron our one valence
electron goes on that outermost shell
all right next let's look at our lewis
dot model a lewis dot model is a
simplified board diagram
it does not show energy levels it only
shows electrons in the valence shell or
the outermost shell
electrons are simply placed around the
element symbol and then we'll look at
lithium again in just a second
all right so lithium same thing as
before um so we would draw our element
symbol and then we would just draw our
valence electron in this case we have
one
so there we go there's our element
symbol and we drew the one
valence electron usually you start at
the top and then work your way
around clockwise so we start with the
first one at the very top and we only
have one
so we finish there
all right go ahead take a minute to
practice by going through the chart
in your packet
all right next let's go through the type
of types of bonds that we have
so elements want to be stable and
because they want to be stable they're
going to
go through the formation of chemical
bonds with other
elements and this is based upon the
octet rule
so it says that elements will gain lose
or share electrons to complete their
valence shell
and become stable like our noble gases
down at the bottom we have co2 and we
can see that
carbon and two oxygens are sharing
electrons
so that they become stable
now going off of the formation of bonds
chemical bonds this is based off of an
attraction between
two atoms resulting from the sharing or
transferring of valence electrons and
how are atoms attracted well it has to
do with their electronegativity which is
a measure of an atom's ability to
attract electrons to itself
so when you look at the periodic table
electronegativity
increases going to the right and going
up
so as you go to the right and up you
have these
most electronegative elements which
would mean
fluorine right here that's going to be
our most electronegative element on the
periodic table
all right so what types of bonds do we
have well firstly we have covalent bonds
and this is when you have two or more
atoms sharing electrons and it's usually
between
two non-metals these will form molecules
and compounds
and it can form up to three bonds a
single bond is
one uh pair of shared electrons
double bond is two pairs of shared
electrons
and then a triple bond is three pairs of
shared
electrons
now there are two types of covalent
bonds we have nonpolar
and polar non-polar covalent bonds is
when you have electrons sharing
being shared equally between two atoms
so for example
two oxygen atoms so here we have the
lewis dot structure for two
oxygens well what's going to happen
we'll see these unpaired electrons
they're going to now be shared equally
between our two
oxygen and so we can now see that that
formed a double bond
because we have two pairs of shared
electrons
all right next we have the polar
covalent bond this is when electrons are
not shared equally between the two atoms
so a good example is water
so here we have oxygen bonded to two
hydrogen because oxygen is more
electronegative it's going to be pulling
on the hydrogen
or pulling on the electrons more which
is why it has a partial
negative charge the hydrogen since
they're less electronegative are going
to have a partial
positive charge
and again this is due to that unequal
sharing of electrons
between our elements
all right next we have ionic bonds this
is the attraction between
oppositely charged atoms or ions and
it's usually between a metal and a
non-metal and it's when a metal
transfers electrons to
the non-metal this is going to form
ionic compounds
and salts a good example
is nacl or sodium chloride or lithium
fluoride now like i said this occurs
when there's a transfer
of electrons so there's a transfer of
electrons from one atom to another atom
forming our ions we have two types of
ions we have a cation which is a
positively charged ion and then an anion
which is a negatively charged ion
and here's an example of sodium chloride
so we can see
that sodium is going to transfer its
electron to chlorine
so it gives up its electron so it's now
n a
plus because it gave up an electron and
then chlorine gained an electron so it's
minus negative
all right and then lastly we have
hydrogen bonds
hydrogen bonds occur when the partially
positive hydrogen
atom in one polar covalent molecule will
be attracted to
an electronegative atom in another polar
covalent molecule
and this even though it's called a bond
isn't actually a bond
it's really an attraction and so it's an
intermolecular think
attraction that forms between molecules
even though it's called a
bond all right so why does this happen
well when a hydrogen atom is bonded to
an electronegative atom think like
oxygen
nitrogen fluorine those really
electronegative atoms
the electrons will not be shared equally
like we saw
in the example of water previously and
remember this is a polar covalent bond
right so we have this unequal sharing of
electrons
so this will cause hydrogen to have a
partial positive charge
and then the electronegative atom will
have a partial
negative charge just like we saw in
water
so let's look at water one more time to
see how these polar covalent bonds will
contribute to hydrogen bonding
all right so we can see that the solid
black lines here these are our polar
covalent bonds
and because we have these partial
positive charges
water molecules would be attracted to
each other so
here for example i'm going to look right
here so here we have one
partial positive hydrogen and we can see
that it's being attractive to the
partial negative oxygen
of another water molecule so again
hydrogen bonding is intermolecular
bonding
between molecules so in the water
molecule itself
so if we were to look at one water
molecule itself
let's say just this right here there's
no hydrogen bonding right we're looking
at polar covalent bonds
but then when you have multiple water
molecules coming together
that's where we see that attraction and
again that attraction
comes from these partial charges due to
the polar covalent bonds
so the partial char positive hydrogen of
one molecule
will be attracted to the partial
negative charge of
another molecule
now one thing to note about water is
that water molecules move a lot
hydrogen bonds form break and reform
with great frequency
and the hydrogen bonds between water is
what makes water more structured than
most
liquids right so let's go ahead
and look at the properties of water now
all right so here's a little overview of
the properties of water we have seven
properties that we're going to cover you
don't need to write this
but let's go ahead and look at polarity
first so this is something that we
already touched on so
again water is a polar molecule we have
unequal sharing of electrons and that's
what makes water
polar and that's also going to
contribute to the intermolecular
hydrogen bonds that form between water
molecules
all right our next property is cohesion
this is an attraction of molecules for
molecules of the same
kind i like to think cooperate
co-cooperate you cooperate
with other people water is cooperating
with other
water molecules why does this happen
well
the hydrogen bonds hydrogen bonds
between water molecules hold them
together
and increase cohesive forces
this is going to be what actually allows
for the transport of water and nutrients
against
gravity in plants it's also going to be
partially responsible for surface
tension which is a property of water
allowing
water to resist external force it's a
property
we see in things besides water too but
in this case we're just focusing on
water
all right and there you go there's
cohesion in that picture there we can
see that hydrogen bond or the dashed
line
between our water molecules causing them
to stick together
all right the next property of water is
adhesion i want you to think add we're
adding something else now so now this is
a cleaning of
one molecule to a different molecule
because we're adding a different
molecule now
this is still due to the polarity of
water but now it's going to be
causing it to be attracted to to
something besides water
now in plants this allows water to cling
to cell walls or in this case
to the xylem which is plant tissue it's
going to allow it to move
still against gravity and it can also
allow it to cling to cell walls
to travel up from root to leaves
all right and there we go there's those
hydrogen bonds forming between
water and the xylem in this case
all right here's a nice image to show
adhesion cohesion together
so again cohesion is water to water
which we can see right here
and then adhesion there's our our water
molecule sticking to
the xylem and each of these together is
going to be
partially contributing to that upward
flow of water through
the xylem now something else that's
going to
also allow for that upward movement of
water through the xylem is capillary
action
so when we have capillary action it's
actually
sort of a combination of forces so it's
cohesion adhesion surface tension all
sort of working together
to create this upward movement now
specifically this will occur when
adhesion is
greater than cohesion so water is more
attracted to the xylem
than it is to other water molecules
this is important for a transport of
water and nutrients in plants
because this is how water is going to
move upwards specifically from
roots to leaves and plants
all right next we have temperature
control firstly high specific heat so
water
can resist changes in temperature
because of hydrogen
bonds in order to break hydrogen bonds
heat has to be absorbed but then when
hydrogen bonds
form heat is released and this almost
stabilizes
the temperature of water so it really
resists changes in temperatures because
of these hydrogen bonds
and how they have to absorb but then
also release
heat now why is
a high specific heat important well it's
going to help mod
moderate air temperature so for example
large bodies of water
they absorb heat in the daytime but then
they release heat
at night it's also going to stabilize
ocean temperature which will benefit
marine life and then organisms can
resist changes in their own internal
temperature because we're
primarily made of water
all right next we have evaporative
cooling water has a very high heat of
vaporization
what that means is that molecules at the
surface
water molecules at the surface with the
highest kinetic energy
can leave as gas all right why is that
important in nature well
it's going to help moderate climate it's
going to stabilize temperatures
in lakes and ponds and then
animals and you know including humans
it's going to prevent us from
overheating right sweat which is
primarily water goes to the surface of
our skin
and those water molecules at the surface
with the highest kinetic energy will
leave as gas and when they do
we get that cooling sensation but it's
also important for
plants it's going to prevent leaves from
being becoming too warm in the sun
and this process is called transpiration
all right and then next we have density
or floating ice
and we know that when ice forms
as or as water solidifies it expands and
it becomes
less dense than liquid water again
everything is due to these hydrogen
bonds
so when cool water molecules move too
slowly
to break these hydrogen bonds remember
earlier i said these hydrogen bonds
break and reform at great frequency well
when water is cooled they can't
because they're moving too slow so they
can't break those hydrogen bonds
so now they get stuck and they form a
crystalline
structure and you can see look how much
space is between the water molecules and
that's because of the hydrogen bonds
forcing water molecules to maintain a
certain distance
from other water molecules and this is
important for
marine life specifically because they
can survive under
ice sheets um thinking like the
antarctic or in very very cold re
regions where water freezes marine life
can still
live under those ice sheets
all right so like i said hydrogen bonds
will help form that crystalline
structure so let's do a quick think fair
share or just think on your own
imagine we had a 3d crystalline
structure of ice how many hydrogen bonds
can
one molecule of water make with its
neighboring water molecules
go ahead go ahead try to work through
this one
well hopefully you said four so if you
think about water in a 3d structure it
can form four
bonds with neighboring water molecules
all right and our last property of water
is at its solvent properties
solvent means a dissolving agent in a
solution
and water is a very versatile solvent
sometimes it's called a universal
solvent
and its polar molecules are attracted to
ions and
other polar molecules that it can form
hydrogen bonds with
and here's a quick review of solution
solvent and solute
if you don't remember these terms just
pause it here so you can look at these
all right so remember water can dissolve
other like substances because life
dissolves light so water can interact
with things like
sugars or proteins that contain lots of
oxygen and hydrogen and what water will
do
so here's our water molecules right here
water will form bonds with the sugar
or the protein and it's going to
dissolve it so you can see it forming
all those little hydrogen bonds it's
gonna start pulling it apart
and eventually it will dissolve
all right what about like ionic
compounds well what will happen
is a partially negative oxygen of water
will interact with the positive
atom so in this case uh this will be
with sodium so oxygen will interact with
sodium so notice how all the
red which in this case that's oxygen
look how they're all oriented towards
sodium and then the partially positive
hydrogen will interact with the
the negative atom which in this case is
chlorine so notice here
look at how all the hydrogen are
interacting
with the chlorine or they orient
themselves
so that they're close to chlorine and
then by doing so we go from
this crystal structure of sodium
chloride
to now it being broken apart because of
water
pulling those ions apart
and eventually it will dissolve the ion
okay we're going to work on the water
properties
station lab in class that'll go through
and highlight some of the important
properties that we just covered
okay but before we do that let's go
ahead and look at a
concept check so i want you to pause the
video here
and i want you to try and work through
each of these
all right that's going to be it for this
video
um next video we'll come back and we're
going to start looking at the
elements of life
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