Transcript 2-2 Properties of water

2-2 Properties of water
What is polarity?
polarity: a compound’s
uneven distribution of
electrons.
Polarity acts like magnets.
polarity: a compound’s
uneven distribution of
electrons.
The hydrogens are attracted to the oxygens of another molecule.
polarity: a compound’s
uneven distribution of
electrons.
What does polarity do?
Causes water to expand when it freezes.
ice
What are hydrogen bonds?
hydrogen bond:
a hydrogen of a compound
is attracted to
another compound’s
negative part.
What is cohesion? Water to water
What is adhesion?
Water to glass (etc.)
What is capillarity?
The adhesion, cohesion and
(air pressure outside the tube) making water go up against gravity.
Water…just like all
matter has a
certain amount of
molecular motion.
At any given moment,
¼ of the molecules
are moving ( or
pushing) up.
Double click on this↓ to see diffusion.
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animations/diffusionV8.html
What is buoyancy?
buoyancy: competition
between molecules
pushing up and gravity
pulling down.
http://www.nisd.net/secww/science/scienc
e-taks/quiz11/fluids%20quiz.htm
8 good questions about buoyancy.
Allow pop-ups for answers to be given.
buoyancy: competition
between molecules
pushing up and
gravity pulling down.
What is viscosity?
viscosity: how thick or
thin a liquid is.
The bigger the number the
thicker (more viscose it is.)
What is a mixture?
Vinegar and baking soda
are not a mixture because
they react.
Vinegar and water
are a mixture
because they
do NOT react.
Magnified salt crystals.
What are solutions?
A homogeneous mixture
solute: the salt alone
solvent: the water alone
solution: the salt and water together
ClCl-
Na+
Na+
Water
Water
http://www.chem.iastate.edu/group/
Greenbowe/sections/projectfolder/fl
ashfiles/thermochem/solutionSalt.ht
ml
Double click on this ↑ to see salt dissolving.
solute: the salt alone
solvent: the water alone
solution: the salt and water together
ClCl-
Na+
Na+
Water
Water
Salt ions being separated by collisions of
water molecules.
suspension: the stuff that
will not dissolve, but
rather sinks or floats.
Blood is partly a suspension.
A glass of river water
is partly a suspension.
What are some solubility tricks?
• Grind large pieces of solute into small
pieces, thereby increasing surface area for
the water molecules to collide into.
• Raise the temperature to increase
collisions of H2O’s into solute.
• Stir or shake which increases the
collisions.
surface area: smaller
particles have more
surface area compared to
one large particle.
surface area: smaller
particles have more
surface area compared to
one large particle.
How much solute can dissolve in
the solvent?
It depends on the conditions
and the properties of the solution being made.
What does supersaturated mean?
There is so much solute,
that there aren’t enough
water molecules
to surround the solute.
How does temperature affect
solubility?
Usually, the warmer, the better.
But gases dissolve better at
lower temperatures.
How does pressure affect solubility?
The more pressure (lid on) the better
the dissolving of a gas in a liquid.
http://www.nisd.net/secww/science/scienc
e-taks/quiz4/solubility_factors_quiz.html
Take this 12 question quiz over solubility.
Allow pop-ups for answers to be given.
Are all solutions liquids?
No
Can electricity go through water?
If it has salts…yes.
If it has sugars or proteins…no.
http://ull.chemistry.uakron.edu/genobc/animations/electrolyte.mov
conduction of electricity:
what ions do in water
Which has the greatest solubility?
CaCO3 or FeS or HgCl2 or
KClO4
Which liquid makes the light shine brighter?
A. A dilute solution of water and ammonia
B. A dilute solution of water and sulfuric acid
The unique properties of water enable life to
exist on Earth. Which of these is a
property of pure water?
F Its solid form is more dense than its liquid.
G It has a low heat absorption capacity.
H It is slightly more acidic than air.
J It dissolves many substances.
According to the law of conservation of
mass, how much zinc was present in the
zinc carbonate?
A student pours mineral salts into a bottle of cold water.
Which of the following best explains why shaking the
bottle will affect the dissolving rate of the salt?
A. Shaking exposes the salts to the solvent more quickly.
B. Shaking helps more water to evaporate.
C. Shaking causes more ions to precipitate out of solution.
D. Shaking equalizes the water temperature.
http://www.glencoe.com/sec/science/le
p_science/physical_science/tutor/quizz
es/test15.html Take this 25 question
quiz to check your understanding of
solubility.
Soda water is a solution of carbon dioxide in
water. This solution is composed of a
F gaseous solute in a gaseous solvent
G liquid solute in a liquid solvent
H gaseous solute in a liquid solvent
J liquid solute in a gaseous solvent
http://www.roomd116.com/Taks%20
Assignments/Solutions.pdf Take this
6 question quiz to check your
understanding of solubility.
Solid KNO3 was added to each beaker.
Each beaker was stirred at the same
rate until all of the solid dissolved. The
table shows the solubilities of KNO3 at
different temperatures. How will the
rates of dissolving compare?
A. KNO3 will dissolve faster in Beaker B
because of increased surface area.
B. KNO3 will dissolve faster in Beaker A
because the water molecules are
farther apart.
C. KNO3 will dissolve faster in Beaker B
because the overall kinetic energy is
increased.
D. KNO3 will dissolve at the same rate in
Beaker A and Beaker B because the
concentrations are the same.
A solution which has a concentration that
exceeds its predicted solubility at a certain
temperature and pressure would be:
A unsaturated.
B saturated.
C supersaturated.
D dilute
What are acids?
Water molecules exist in equilibrium with
hydrogen ions and hydroxide ions.
H2O ↔ H+ + OH-
OH-
H+
What are acids?
Water molecules exist in equilibrium with
hydrogen ions and hydroxide ions.
H2O ↔ H+ + OH-
or
OH-
H+
What are acids?
Water molecules exist in equilibrium with
hydrogen ions and hydroxide ions.
H2O ↔ H+ + OH-
Just a proton
=
OH-
H+
What are acids?
Water molecules exist in equilibrium with
hydrogen ions and hydroxide ions.
H2O ↔ H+ + OH-
Hydrogen ions wish
they had their electron back.
They feel naked without an electron.
OH-
H+
These are all acids because the
hydrogens all transfer their
electron to the other elements, then
are left as a solitary proton that
would like any electron from any
HCl
element
nearby.
H SO
2
3
HNO2
H3PO2
HNO4
H2SO5
HI
Even though these compounds have
hydrogens, none of them are acids
because none of the hydrogens
“transferred” the electron.
They are all sharing electrons and
therefore do not feel naked.
Acid: naked hydrogen ions,
pH of 0 → 6.9
Base: OH ions searching for
another hydrogen,
pH of 7.1 → 14
What is the pH scale?
Concentrated acid
can be diluted by adding more water.
What are buffers?
Weak acids or bases that can react
with strong acids or bases
to prevent sharp, sudden changes in pH.
pH indicators
Litmus paper tells acid or base
pH paper tells pH numbers
Approximate the pH of the
Water
Apples
Beans
Milk
Shrimp
pH and its effect on reactions
Take this 25 question quiz to check your understanding of pH.
http://www.glencoe.com/sec/science/lep_sci
ence/physical_science/tutor/quizzes/test17.
html
What is the difference between:
strong acid and a weak acid?
Double click this↓ to see hydrogens transferring.
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animations/HCl(aq).html
3 out of 3
transferred
1 out of 3
transferred
6 out of 6
transferred
2 out of 6
transferred
Water is the
universal
solvent
because of
its amazing
properties
which are
mostly due to
its polarity.
The table below shows the pH values of
samples of substances.
According to the table, which of these
substances is basic?
A. rainwater.
B. drain cleaner.
C. distilled water.
D. soda water.
The water from hot springs near the Ebeko
volcano in the Pacific Ocean has a very
low pH. A low pH indicates which of the
following about the water?
A. It has no detectable H+ or OH- ions.
B. It has equal concentrations of H+ and
OH- ions.
C. It has high concentrations of H+ ions.
D. It has equal numbers of positive and
negative ions.
A student was assigned to take water
samples from a lake near his home. He
measured the pH of one of the water
samples to be 6.0. Which of the following
best describes this sample of water?
A. highly acidic
B. slightly acidic
C. highly basic
D. slightly basic
A patient has chronic indigestion due to an
overproduction of stomach acid. Which foods
should the patient avoid until the condition is
resolved?
A. vegetables.
B. citrus.
C. dairy/egg.
D. starches.
The reaction catalyzed by the
bacterial enzyme
ß-galactosidase forms a darkcolored end-product when the
cells are grown on a particular
agar medium.
As more product is formed, the
cells become darker. Students
performed an experiment to
determine the optimum pH for
activity of this enzyme.
Their results are shown in the
illustration of bacterial
colonies.
Based on these data,
the students should
conclude that ßgalactosidase
functions best at
which pH?
A.5
B.7
C.9
D.11
If a lab group were using hydrochloric acid
to perform a substitution reaction, which
precaution would not be a concern?
A Flammability
B Health
C Reactivity
D Contact