Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 1
Atoms, Molecules, and Seawater Chemistry Lecture Notes
We will learn about the “Atomic Theory of Matter” – all of chemistry – in just a few hours!
Of course, we will focus on what we will need to know about the chemistry of water and
seawater for the rest of the semester.
Atoms & Molecules
All materials are composed of incredibly tiny objects called “atoms.”
Air, wood, water, oil, steel, plastic, etc. – just about anything you can think of is made of atoms.
What is a molecule?
Give an example of a molecule.
The special properties of a material depend on which atoms it is made of
AND how its atom or molecules:
• “bond” with one another and other atoms and molecules (“bond” = “join together” or “link”)
• are moving: fast or slow, flying around or vibrating or spinning, etc.
In other words, water is not only different from oil because it is made from different atoms;
water is also different from oil because of how water molecules bond with other atoms and
molecules and how the water molecules are moving.
Materials change when their atoms bond or break their bonds, speed up or slow down, etc.
In general, atoms are NEVER destroyed when materials change: they are just rearranged.
(Exceptions include the extreme conditions inside stars and radioactive atoms.)
Give an example of how atoms are “recycled.”
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 2
Structure of an Atom (Lab Station #8 – pages 17 and 18)
Proton
Neutron
Where?
Weight
Electric Charge
What force holds atoms together?
How does the force work? In other words,
what are the rules of attraction and repulsion?
nucleus
electron
What force holds molecules together?
Electron
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 3
Review Questions
What force “bonds” atoms together?
______
What force “bonds” molecules together?
______
a. Charge
b. Covalent
c. Electric
d. Gravity
e. Hydrogen
f. Ionic
What would happen if two electrons were brought close together?
a. pulled together strongly
b. pulled together weakly
c. pushed apart strongly
d. pushed apart weakly
What missing from or “not quite right” in the following statement?
Water molecules are stronger than alcohol molecules.
What missing from or “not quite right” in the following statement?
Water bonds are closer together than alcohol bonds.
Practice Questions
1. Are atoms “used up” by our bodies
or can they be “re-used” again and again?
“Used Up” / “Re-used”
2. Which of the following are “heavy” atomic particles?
(Circle all that apply.)
Electron / Neutron / Proton
3. Which of the following are found in the nucleus of an atom? Electron / Neutron / Proton
(Circle all that apply.)
4. What kind of electric charge does a proton have?
Positive / Negative / No Charge
What kind of electric charge does an electron have?
Positive / Negative / No Charge
What kind of electric charge does a neutron have?
Positive / Negative / No Charge
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 4
Bonding Strength
Based on your own experience, which would you expect to have the strongest bonds
between its atoms (or molecules), a solid or a gas? Why?
Bonds between Atoms
Bonds with
Water Molecules
Bonds between
Non-Water Molecules
What are the bonds formed by water molecules called?
Are these bonds unusually strong or weak? 1
Water molecules are “dipolar.” What does this mean?
1
Unusually “strong or “weak” compared to the bonds formed by other small molecules like water.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 5
Adhesion, Cohesion, & Surface Tension (Lab Station #1: pages 3 and 4)
Because water molecules have both a positive side and a negative side,
they are attracted to nearly everything.
Consider the experiment in which we observed drops of water and alcohol on slides.
What did this experiment indicate about the relative strength of the bonds formed by water
molecules and alcohol molecules? In other words, are the bonds formed by water molecules
stronger or weaker than the bonds formed by alcohol molecules? Explain your reasoning.
In a drop of water, the molecules of the liquid are constantly resisting
the force of (A)______________________ which is trying to pull them downwards and apart.
The drop of (B)__________________ was higher than the drop of (B)___________________.
The drop of (B)__________________ spread out more than the drop of (B)_________________.
The molecules of (B) ____________________ did NOT remain together as well as
the molecules of (B) ____________________, because the (C)____________________ bonds
that existed between the alcohol molecules were more easily “broken.”
A: give the name of the force
B: alcohol, water
C: stronger, weaker
Consider the experiment in which we observed how liquids like alcohol and water naturally
climb up thin tubes which are inserted into them.
What did this experiment indicate about the relative strength of the bonds formed by water
molecules and alcohol molecules? In other words, are the bonds formed by water molecules
stronger or weaker than the bonds formed by alcohol molecules? Explain your reasoning.
We can see that the molecules of liquids in the thin tubes were attracted to the molecules
of the (A)_____________________, because the liquids rose upwards against the force of
(B)___________________________.
Since the molecules of (C)_________________________ were better able to overcome this
force and rose up higher than the molecules of (C)_________________________, molecules
of water must form (D)___________________________ bonds than molecules of alcohol.
A: air, tube
B: give the name of the force
C: alcohol, water
D: stronger, weaker
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 6
Water, The Universal Solvent: Dissolving Solids (Lab Station #2 – pages 5 through 8)
How is a “dissolved” salt atom different from a salt atom in a grain of salt?
(Hint: Discuss the bonding and motion of the salt atom.)
A dissolved salt atom is bonded to a group of ____________________ molecules.
while in a grain of salt, salt atoms are bonded to other __________________ atoms.
Which are stronger, the bonds between salt atoms or the bonds between water molecules?
Why? (How can you tell? Why do you think so?)
The bonds between ________________ are stronger than the bonds between ______________,
because it is harder to break ____________________ substances.
How does water dissolve other substances? Describe what the water molecules do.
The __________________________ attraction of a ___________________ of water molecules
is stronger than the attraction of a single salt atom. The water molecules pull salt atoms away
from their neighbors and surround them.
Why didn’t the saltwater dissolve as much salt as the fresh water?
In saltwater, many of the water molecules are already ______________ to salt atoms,
so they are unable to go bond with new salt atoms that are added to the water.
Why didn’t the alcohol dissolve as much salt as the fresh water?
Alcohol molecules form ______________________ bonds than water molecules,
so a ______________ group of alcohol molecules is needed to pull salt atoms away from their
neighbors. Since more alcohol molecules are needed to dissolve each atom of salt, more alcohol
than water is also needed to dissolve salt.
Why don’t salts and nutrients fall to the bottom of the ocean?
Salts and nutrients are dissolved in ocean water, so their atoms or molecules are
____________________ to groups of water molecules. They stay with their group,
which floats or sinks to the appropriate depth according the overall density of the group.
Salt atoms typically weigh ______________ than water molecules, so a dissolved salt atom
typically ___________________ the density of the group of water molecules surrounding it.
Molecules of dissolved gases like oxygen and carbon dioxide are also bonded with water
molecules. So long as they are surrounded by and bonded water molecules, it is difficult for them
to escape the ocean.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 7
Review Question
Water molecules dissolve salt, because their bonds are stronger than the bonds between the salt atoms.
a. True
b. False
Practice Questions
1. Is it easier to break the bond between two atoms in a molecule or is it easier to break the bond
between two molecules? In other words, which can be separated more easily, the atoms or molecules?
It is easier to break the bond between (separate) the two Atoms / Molecules.
2. Is water an excellent solvent or a poor solvent?
Can water dissolve all substances?
Excellent / Poor
Water dissolves All / Most / Few Substances
3. Which bonds are stronger, the bonds between salt atoms or the bonds formed by water molecules?
How is water able to dissolve salt?
● bonds formed between salt atoms:
water molecules’ sharp, triangular shape helps them separate salt atoms
● bonds formed between salt atoms:
only a group of water molecules pulling together are strong enough to pull salt atoms apart
● bonds formed between water molecules:
water molecules have very strong bonds that can easily pull salt atoms apart
● bonds formed between water molecules:
because water molecules are dipolar, so both positive and negative salt atoms are attracted to them
4. Why is fresh water able to dissolve more salt than salt water?
● fresh-water molecules are dipolar
● fresh-water molecules can form more bonds in more directions than salt-water molecules
● fresh-water molecules form stronger bonds than salt-water molecules
● in fresh water, there are more water molecules which have not bonded with salt atoms (yet)
● in fresh water, there are many more water molecules (10 times more) than in salty water
● in fresh water, there is more room for atoms and molecules to move around
● in fresh water: easier for a group of water molecules to surround salt atoms (less salt in the way)
5. Which dissolves more salt, alcohol or fresh water?
Why is one able to dissolve more salt?
● Alcohol: alcohol molecules can form more bonds in more directions than water molecules
● Alcohol: alcohol molecules form stronger bonds than water molecules
● Alcohol: alcohol molecules are smaller, allowing more of them to surround & pull on the salt atoms
● Water: water molecules can form more bonds in more directions than alcohol molecules
● Water: water molecules form stronger bonds than alcohol molecules
● Water: water molecules’ sharp, triangular shape helps them separate salt atoms
6. Do salts and nutrients dissolved in ocean water slowly sink towards the bottom of the ocean?
Why or why not?
● sink: the surface area of salt atoms and nutrient molecules is too large
● sink: salt atoms and nutrient molecules More / Less dense that water molecules
● do not sink: salt atoms and nutrient molecules are bonded to the water molecules
● do not sink: salt atoms and nutrient molecules are More / Less dense than water molecules
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 8
Calculating Salinity
About 3.5% of seawater is “salt;” the other 96.5% is water. (Remember: “salt” means all the substances
dissolved in ocean water which include gases like oxygen and nutrients like phosphate, not just the
components of ordinary salt, sodium and chlorine.) Oceanographers typically describe salinity in terms of
“parts per thousandth” (‰ or ppt), not percentages, so oceanographers would say that the ocean has an
average salinity of 35 “parts per thousandth.”
Why do oceanographers do this? Scientists use the metric system (mathematically, it is a lot easier, and
doing science is hard enough without making the math harder). If they report their measurements in parts
per thousandth, then they can quickly determine how much salt is in the water: 1 part per thousandth is
about 1 gram of salt per liter of seawater. (A liter is half of a large bottle of soda. A gallon is a little less
than 4 liters.) So, if the ocean’s salinity is typically about 35‰, then there is about 35 grams of salt in
each liter of seawater.
It is very easy to convert from percentages (“parts per hundredth”) to parts per thousandth: just move the
decimal point to the right by one place. So, 2.0% is 20‰, 3.1% is 31‰, 4.7% is 47‰, and so on. This
works because 2 out of 100 (2/100 = 0.02) is the same as 20 out of 1000 (20/1000 = 0.02).
Water is rarely “pure.” Good tasting tap water, for example, has a salinity below 0.6‰. In coastal areas
which get lots of “fresh” water runoff, salinities may be as low as 10‰. We call this water “brackish.”
places with little rainfall and lots of evaporation, the seawater salinity be over 40‰, and we say the water
“hypersaline” or “briny.”
To calculate the salinity of a solution, just divide the amount of salt by the total amount of salt water that
is made. For example, suppose that we mixed 2.5 grams of salt with 100 grams of water. The total
amount of salt water would be 102.5 grams. So,
2.5 grams of salt / 102.5 grams of salt water = 0.0243
To make this into a percentage, we need to multiply by 100, so we’d get a salinity of 2.43%.
To make this into parts per thousandth, we need to multiply by 1000, so we’d get a salinity of 24.3‰.
To make it easier to measure ocean salinity, in 1978 oceanographers changed from using “parts per
thousandth” to “practical salinity units” (psu). 1 psu is about 1‰, so I am not going to worry about the
difference, and will use parts per thousandth just like your textbook does. The change was made because
oceanographers typically determine seawater’s salinity by measuring its conductivity (salts are
electrically charged atoms – ions – so they conduct electricity). Psu is determined by comparing the
conductivity of a sample of seawater to the conductivity of a specially made salty solution.
Practice Questions
How salty is the ocean? (Answer in parts per thousandth.)
______________
How salty is the ocean? (Answer in parts per hundredth.)
______________
Suppose some water has a salinity of 51‰.
What is its salinity in parts per hundredth (%, a percentage)?
______________
Suppose some water has a salinity of 0.2%.
What is its salinity in parts per thousandth (‰)?
______________
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 9
pH: Acids, Bases (Alkalines), and Buffering (Lab Stations #5 and 6 – pages 11 through 14)
Acidic
Neutral
Basic (Alkaline)
pH
In general, is ocean water a little acidic or a little basic?
Which became more acidic when you added acid to it, fresh water or seawater?
Why did fresh water and seawater react differently when acid was added to them?
If ocean water becomes too acidic, bicarbonate and carbonate molecules dissolved in
ocean water will absorb the acid, which brings the pH of the ocean back towards neutral.
When they absorb acid, the bicarbonate molecules become carbonic acid molecules,
and the carbonate molecules become bicarbonate molecules.
If ocean water becomes too basic, carbonic acid and bicarbonate molecules in ocean water
will release acid. The acid combines with the bases and become water, which is neutral.
When they release acid, the carbonic acid molecules become bicarbonate molecules, and
the bicarbonate molecules become carbonate molecules.
When humans burn fossil fuels like oil and coal, we release large amounts of carbon dioxide
from the atmosphere. The ocean absorbs about half of this carbon dioxide which is good for us,
because by removing so much of our carbon dioxide pollution from the atmosphere, it keeps the
carbon dioxide from enhancing the greenhouse effect even more and further warming the planet.
Unfortunately, though,…
When carbon dioxide enters the ocean, how does it affect the pH of ocean water?
How does the change in pH affect ocean life?
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 10
Practice Questions
When this carbon dioxide (CO 2 ) enters the ocean,
does the ocean become more acidic or more basic (alkaline)?
________________________
Does the carbon dioxide raise or lower the pH of ocean water?
________________________
Which changes the most when acids & bases are added,
the pH of ocean water or the pH of fresh water?
_______________________
How is ocean life affected by the extra carbon dioxide?
Studies have shown that it:
● burns animal’s ears
● burns animal’s eyes
● dissolves calcium carbonate shells
● dissolves silica shells
● makes it harder to breathe
● promotes photosynthesis
● has no measurable effect on ocean life
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 11
Temperature, Heat, and Phases (Solids, Liquids, and Gases) (Station #4 – page 10)
How are hot molecules different from cold molecules?
What evidence of this did we observe during the lab?
If you wanted to transform liquid water into water vapor (a gas), what would you do?
Why does this cause the water molecules to fly apart?
In other words, why does this cause the bonds between water molecules to “break”?
Water molecules are bonded (held together) by _______________________ attraction.
When heat is added to water, the water molecules move (A)______________________
and this motion carries them (B)__________________________________________,
which makes the attraction between the molecules (C)_______________________.
If they move far enough apart, the attraction will weaken enough for them to break free
of one another and fly apart. (weak or no attraction = broken bond, no bond)
A: faster, slower
B: closer together, farther apart
C: stronger, weaker
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 12
Solid
Liquid
Gas
Is it better to wash your “crusty” dishes in hot water or cold water? Why?
Explain by describing the behavior of their atoms and molecules.
Will “delicate” clothing bleed if you wash it in hot water or in cold water? Why?
Explain by describing the behavior of their atoms and molecules.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 13
Practice Questions
1. If you heat an object, do its atoms (or molecules) move faster or slower?
____________
What evidence have you seen that supports your belief that adding or removing heat
changes the speed of the atoms (or molecules) of an object?
(Choose ONE observation below that best supports your belief.)
● The boiling point of water is 100oC.
● The water appeared to be boiling at less than 100oC.
● Drop of dye spreading out in a tank of water without stirring
● Drops of dye spreading out in warm and cold water: warm dye spread out faster
● Drops of dye spreading out in warm and cold water: cold dye spread out faster
● Looked at hot and cold molecules using a microscope.
● Steam comes out of water before it reaches the boiling point.
● Steam does not come out of water until it reaches the boiling point.
2. For a given material, how would you rank the strength of the attractive forces (bonds)
between atoms and molecules in the gas, liquid, and solid states?
The ____________ state has the particles which are most strongly attracted to one another.
The ____________ state has the particles which are most weakly attracted to one another.
3. For a given material, how would you rank the average speed of the atoms and molecules in
the gas, liquid, and solid states?
The ___________________ state has the particles with the highest average speed.
The ___________________ state has the particles with the lowest average speed.
4. In which state – gas, liquid, or solid – are there no bonds between the atoms and molecules
of a material?
● gas
● liquid
● solid
● There are bonds between the atoms and molecules in all 3 states.
5. Describe the motion of the atoms and molecules of a gas.
● do not move
● constantly vibrate in place
● constantly move from place to place
Describe the motion of the atoms and molecules of a liquid.
● do not move
● constantly vibrate in place
● constantly move from place to place
Describe the motion of the atoms and molecules of a solid.
● do not move
● constantly vibrate in place
● constantly move from place to place
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 14
Latent Heat (Lab Station #3 – pages 8 and 9)
Latent heat is the amount of heat that must be added to a substance to make it transform from a
solid to ________________ or a liquid to a ________________, or the amount of heat that must
be lost by (removed from) a substance to make it transform from a gas to a ________________
or a liquid to a ________________.
Possible Answers: gas, liquid, solid
What words indicate that latent heat has been added or removed?
Situation: “Water evaporates off your skin.”
The ________________________________ is gaining latent heat.
The ________________________________ is losing heat.
Bonds between the molecules of water and skin are ___________________________.
Situation: “A raindrop forms in the atmosphere.”
The ________________________________ is gaining heat.
The ________________________________ is losing heat latent heat.
Bonds between the molecules of water are ___________________________.
Does water have a high or low latent heat compared to other substances?
What does this mean? In other words, how does it react differently to being heated?
Why is water’s latent heat different from the latent heat of other substances?
Water has a _____________________ latent heat than other substances which means that
______________ heat must be added to water molecules to make them evaporate or melt, and
______________ heat must be removed from water molecules to make them condense or freeze.
It is harder to make water transform than other substances, because liquid water molecules
form unusually _________________ bonds, and it takes more heat to break strong bonds and
more heat must be removed to create strong bonds.
All living things 2 need liquid water. Compared to other small, simple, and abundant molecules,
water stays solid until it reaches a much higher temperature, remains a liquid over a large range
of temperatures, and stays in a liquid form until a much higher temperature.
2
At least, all known living things need liquid water.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 15
Thermal Expansion & Contraction
If you heat an object, it does not immediately
transform (evaporate or melt). First, it expands.
Why does heating an object make it expand
(get larger)? Explain by describing the
behavior of its atoms or molecules.
Warm Atoms
Cold Atoms
Does this make the object’s density higher or lower?
Why does cooling an object make it contract (get smaller)?
Explain by describing the behavior of its atoms or molecules.
When an object loses heat, the molecules wiggle (A)_______________________________,
so the (D)_____________________________________ attraction they feel for one another
is then able to pull them (B)___________________________________________________.
This (C)___________________ the strength of the attraction that they feel for one another.
A: faster, slower
B: farther apart, closer together
C: increases, decreases
O
D: give the name of the force that bonds the molecules together
O
Freezing water into ice is an exception to the rule that cooling an object will make
it smaller. Unlike just about every other substance, when water is cooled to the
O Empty
freezing point, it expands, which is why ice floats in water. Water molecules can
Space
O
only form strong bonds in certain, specific directions (away from each atom, like
the points of a triangle). Thus, a “gap” or “hole” is left in the middle of the
molecules when water molecules bond strongly with one another at these angles in a
“ring.” (You can see evidence for this in the shape of a snowflake.) In a liquid form, water
molecules are moving around and can move through this space, so liquid water takes up less
space (is smaller) than solid water (ice).
O
O
Freezing Seawater
Salt atoms “get in the way” when seawater freezes; they do not fit into the ice crystal (cannot
bond in the correct directions) so much of the salt remains in the ocean when seawater freezes.
Seawater has a ____________________ freezing point than fresh water.
In other words, it is easier to freeze ____________ water than to freeze ____________ water.
The salt that is “rejected” by the ice stays in the ocean, making the ocean water _______________.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 16
Heat Capacity (Lab Station #7 – pages 15 and 16)
Which is warmer on a hot afternoon at the beach, the sand or the water?
Which gained more heat from the Sun?
The ___________________ is warmer than the ____________________
even though both gained the ______________ amount of heat from the Sun.
This suggests that different substances may react differently when they absorb heat
(their temperatures change by different amounts given the same amount of heat).
Describe how water’s reaction to heating and cooling differs from that of other substances.
When water gains heat, its temperatures goes up ______________
than the temperature of most substances.
When water loses heat, its temperatures goes down ______________
than the temperature of most substances.
We describe this behavior by saying that water has a _______________ heat capacity
than most substances.
Why? These observations indicate that water “holds” more heat than other substances
at the same temperature, because it took more heat to raise water to that temperature.
In what ways is the climate “better” near the coast than farther inland?
The climate near the coast is ____________________________ than the climate farther inland.
Possible Answers: warmer, cooler, more moderate (less extreme)
Why is the climate “better” near the coast?
Winds blow air that has been heated or cooled by the (A) _______________ to the coast
whereas the air inland is heat or cooled by the (A) _______________.
During the summer, the (A) _______________ is warmer than the (A) _______________ ,
so ocean breezes make the coastal climate (B) _________________ than farther inland.
During the winter, the (A) _______________ is colder than the (A) _______________ ,
so ocean breezes make the coastal climate (B) _________________ than farther inland.
A: land, ocean
B: warmer, cooler
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 17
Practice Questions
1. What is gaining heat in the following situation? What is losing heat?
“Water freezes into ice at the surface of a lake.”
The lake water is ______________________________ heat, and
the atmosphere is ______________________________ heat.
2. Compared to other substances, do you have to add or remove a lot of heat or only a little heat
to make water vapor (i.e., steam, a gas) transform into liquid water?
● add a lot of heat
● add a little heat
● remove a lot of heat
● remove a little heat
Compared to other substances, do you have to add or remove a lot of heat or only a little
to make ice transform into liquid water?
● add a lot of heat
● add a little heat
● remove a lot of heat
● remove a little heat
3. “Most of our drinking water was originally in the ocean.”
● True: salt evaporates from the ocean,
leaving behind fresh water that we take from the ocean
● True: water evaporates from the ocean, leaving the salt behind,
and then falls as rain and snow
● True: we use “desalinization” plants to remove the salt
● False: most of our water comes from snow melting up in the mountains
● False: most of our water comes from aquifers (underground water, “groundwater”)
4. When seawater freezes into ice, what happens to the salt in the seawater that freezes?
Is the salt inside the ice, or does it get left behind in the ocean water?
The salt is ________________________________________________________.
How does the freezing of seawater affect the salinity of the nearby ocean water (the water that
does not freeze)? Does the ocean water get saltier or less salty?
The ocean water that does not freeze gets ________________________________.
Does salt make it easier or harder for water to freeze?
In other words, does salty water freeze at a higher or lower temperature than fresh water?
Salt makes it _______________________________ for water to freeze.
In other words, salty water has a _____________________ freezing point that fresh water.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 18
Practice Questions
5. If you heat an object or substance, does it get larger or smaller?
__________________
If you add heat to an object (“warm it”), will the bonds between its molecules become
stronger or weaker? Why would this cause bonds to grow stronger or weaker?
The bonds between the object’s molecules become (A)________________________
because the molecules wiggle (B)_________________________________
so they (C) ___________________________________________________.
This (D) ____________________________________________the strength
of the (E) ________________________________________________ force.
6. If you cool an object or substance, does it get larger or smaller?
__________________
If you remove heat to an object (“cool it”), will the bonds between its molecules become
stronger or weaker? Why would this cause bonds to grow stronger or weaker?
The bonds between the object’s molecules become (A)________________________
because the molecules wiggle (B)_________________________________
so they (C) ___________________________________________________.
This (D) ____________________________________________the strength
of the (E) ________________________________________________ force.
A: stronger, weaker
B: faster, slower
C: get bigger, get smaller, move closer together, move farther apart, spin faster, spin slower
D: increases, decreases
E: give the name of the force that bonds the molecules together
7. Land and ocean both warm and cool the air above them. Unlike farther inland, the climate by
the coast is affected by air that has been in contact with the ocean, because winds blow ocean
air to the coast.
The climate inland is (A)____________________ than the coastal climate during the summer
and climate inland (A)____________________ than the coastal climate during the winter.
because the (B)_____________________________ of ocean water is
(C) _________________________ the (B)_____________________________ of the land.
A: warmer, cooler, about the same
B: boiling point, density, heat capacity, latent heat, solubility, surface tension, viscosity
C: higher than, lower than, about the same as
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 19
Atoms & Molecules Never Stop Moving (Lab Station #4 – page 10)
What is diffusion?
Atoms and molecules in liquids and gases naturally tend to spread out over time.
How did we observe diffusion during the lab?
Why is this observation good evidence that atoms & molecules never stop moving?
The water was left to “rest.” In other words, the water molecules were given time
to slow down and stop.
The water was quite calm and still, yet we could see the dye ________________ in water
that appeared to be motionless, so the water molecules themselves were still moving.
Note: “Friction” between objects causes objects we can see to slow down. However, “friction”
does NOT exist at the level of atoms and molecules. They simply hit one another, which causes
one to speed up and another to slow down; no energy is “lost.” Objects we can see “slow
down” because the organized motion of the atoms and molecules (all of them are moving in the
same direction) breaks down and becomes disorganized, random motion (heat) because atoms
and molecules of one object are rubbing and bumping against those of another object.
Why Heat Flows from Hot Objects to Cold Objects
What IS “heat”?
Heat is the motion of atoms and molecules. Hot molecules have ________________ heat and
move _______________________ than cold molecules.
How is “heat” transmitted from one atom or molecule to another atom or molecule?
After most collisions, the faster-moving object slows down and the slower-moving object speeds up.
Why does heat flow from hot objects to cold objects?
When “hot” objects are put next to cold objects, their molecules bump into one another.
As a result of the collisions between the molecules,
the “hot” molecules (A)__________________________ (which means they cool down) and
the “cold” molecules (A)__________________________ (which means they warm up).
A: speed up, slow down
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 20
Review Questions
Warm water molecules move faster than cold water molecules.
a. True
b. False
Molecules of water vapor (gas) move faster than molecules of liquid water.
a. True
b. False
Bonds between liquid water molecules are stronger than
the bonds between water molecules in ice.
a. True
b. False
If a solid is hot, its molecules are flying around very fast.
a. True
b. False
If you cool water molecules, they contract (i.e., shrink, get smaller).
a. True
b. False
Do atoms and molecules ever stop moving?
a. Yes, they can stop moving.
b. No, they never stop moving.
How do atoms & molecules transfer heat?
a. when they bond
b. when they break their bonds
c. when they bump into one another
d. when they give off latent heat
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 21
Practice Questions
1. Do atoms and molecules ever stop moving,
even those in a cube of ice, a tranquil pool of water, or calm air? ______________________
What evidence have you seen that supports your belief?
(Choose ONE observation below that best supports your belief.)
● Drop of dye spreading out in a tank of water without stirring
● Drops of dye spreading out in warm and cold water: warm dye spread out faster
● Looked at the molecules using a microscope.
● Steam comes out of water before it reaches the boiling point.
2. Why does heat always flow from a hot object to a cold object?
“Hot” molecules move (A) _______________________________ than “cold” molecules.
When “hot” molecules (B) ____________________________________ “cold molecules,”
the “hot” molecules (C)_________________________ (which means they cool down) and
the “cold” molecules (C)________________________ (which means they warm up).
A: faster, slower
B: bond with, break their bonds with, collide with, release latent heat to
C: speed up, slow down
3. Describe the molecules in the situation below using the atomic theory of matter.
“An iceberg melts in the ocean.”
Initially the water molecules of the ice are (A)___________________________________,
and the water molecules of the ocean are (A)_______________________________________.
The molecules of the ice are moving (B)______________ than the molecules of the ocean,
so when the water molecules of the ice (C)_______________________________________
the molecules of the ocean water, the water molecules of the ice (D)____________________.
As a result of this change in speed, the water molecules of ice:
(Mark all that apply.)
● break their bonds with the other water molecules of the ice
● break their bonds with the molecules of the ocean water
● loosen (weaken) their bonds with the other water molecules of the ice
● loosen (weaken) their bonds with the molecules of the ocean water
● form new bonds with the other water molecules of the ice
● form new bonds with the molecules of the ocean water
● form stronger bonds with the other water molecules of the ice
● form stronger bonds with the molecules the ocean water
A: moving around from place to place, vibrating in place, not moving at all
B: faster, slower
C: bond with, break their bonds with, collide with, absorb latent heat from
D: speed up, slow down
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 22
Applying the Atomic Theory of Matter to Everyday Situations
Explain what is happening in each situation using the atomic theory of matter. In other words,
you need to discuss the bonding between atoms and/or molecules, and the motion of the atoms
and/or molecules, and show how they produce the changes in the beverage.
Situation: Steam rises from a hot cup of coffee or tea. You pour some milk and
sugar crystals into the beverage; the sugar crystals sink to the bottom of the cup.
You get distracted and forget about the coffee or tea. The coffee or tea slowly
cools down and changes color: the lighter regions where the milk was poured
become darker and the dark regions become lighter, until the coffee or tea is
all one uniform color. Later, you notice the cup of coffee or tea, and take a sip;
it tastes sweet.
(a) Why does steam rise from hot beverage? In other words, which atoms and/or molecules are
rising from the drink? Why are they rising from the drink? Why do the other atoms and/or
molecules stay behind in the drink? As part of your answer, discuss how the molecules of a
gas are different from those of a liquid.
(b) Why does the beverage cool down over time? As part of your answer, discuss how hot
molecules are different from cold molecules, and explain how or why heat is transmitted
from one molecule to another one.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 23
(c) Why does the color of the beverage change over time? In other words, what are the atoms
and/or molecules doing that produces the change in color of all of the liquid in the cup?
(d) How or why did the beverage become sweet? In other words, what are the atoms and/or
molecules doing that produces the change in the taste of the drink? As a part of your answer,
discuss how the molecules of a solid are different from those of a liquid.
Atoms, Molecules, and Seawater Chemistry Lecture Notes (Topic 4A) – page 24
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