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.

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animations/diffusionV8.html

Double click on this↓ to see diffusion.

What is buoyancy?

buoyancy: competition between molecules pushing up and gravity pulling down.

http://www.nisd.net/secww/science/science-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 sodaare not a mixture because they react.

Vinegar and water are a mixture because they do NOT react.

What are solutions?

Magnified salt crystals.

A homogeneous mixture

Cl-

Water

Cl-

Na+

Water

Na+

solute: the salt alone

solvent: the water alone

solution: the salt and water together

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/thermochem/solutionSalt.html

Double click on this ↑ to see salt dissolving.

Cl-

Water

Cl-

Na+

Water

Na+

solute: the salt alone

solvent: the water alone

solution: the salt and water together

Salt ions being separated by collisions of water molecules.

Blood is partly a suspension.

A glass of river water is partly a suspension.

suspension: the stuff that will not dissolve, but rather sinks or floats.

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/science-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/lep_science/physical_science/tutor/quizzes/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%20Assignments/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-

H+OH-

What are acids?

Water molecules exist in equilibrium with hydrogen ions and hydroxide ions.

H2O ↔ H+ + OH-

H+OH-

or

What are acids?

Water molecules exist in equilibrium with hydrogen ions and hydroxide ions.

H2O ↔ H+ + OH-

H+OH-

=

Just a proton

What are acids?

Water molecules exist in equilibrium with hydrogen ions and hydroxide ions.

H2O ↔ H+ + OH-

H+OH-

Hydrogen ions wish they had their electron back.They feel naked without an electron.

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

element nearby.HCl

H2SO3

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 indicatorspH paper tells pH numbersLitmus paper tells acid or base

Approximate the pH of the

WaterApplesBeansMilkShrimp

pH and its effect on reactions

http://www.glencoe.com/sec/science/lep_science/physical_science/tutor/quizzes/test17.html

Take this 25 question quiz to check your understanding of pH.

What is the difference between: strong acid and a weak acid?

3 out of 3transferred

1 out of 3transferred

6 out of 6transferred

2 out of 6 transferred

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animations/HCl(aq).html Double click this↓ to see hydrogens transferring.

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 dark-colored 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 ß-galactosidase functions best at which pH?

A.5B.7 C.9D.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