8/17/2015
Miss Kennedy
Properties of Water
Section 2-2 pgs 40-43
The Water Molecule
● Like all molecules, a water molecules is neutral, because it has 10 protons and 10
____________________ which balance each other out
● An ______________________ atom has a much stronger attraction for electrons than the
hydrogen atom
● This is because it has a greater number of protons.
● Therefore, there’s a higher chance of finding shared electrons near the oxygen atom than
near the hydrogen atom.
● The water molecule has a _____________ shape, meaning the oxygen atom is on one end
of the molecule and the hydrogen atoms are at the other.
● As a result, the oxygen end of the molecule has a slight _________________________
charge and the hydrogen end of the molecule has a slight
___________________________ charge.
● A molecule in which the charges are unevenly distributed is called a
______________________ molecule because it’s like a magnet with poles.
● The water molecule is polar because, due to the difference in the number of protons, there
is an uneven distribution of electrons between the oxygen and hydrogen atoms.
● The __________________________________________ is near the oxygen atom, and
the ____________________________________________ is near the hydrogen atoms.
● Because they have partial positive and negative charges, polar molecules such as water
can attract each other.
● The attraction between the hydrogen atom on one water molecule and the oxygen atom
on another is an example of a ______________________________________________.
● Hydrogen bonds aren’t as strong as covalent or ionic bonds, but water’s ability to form as
many as _____________________ hydrogen bonds at one time is responsible for many
of its special properties.
● Two of these properties are called __________________________ and
_________________________.
8/17/2015
Miss Kennedy
● _____________________________ is an attraction between molecules of the same
substance.
● Because of hydrogen bonding, water is extremely cohesive, causing molecules on the
surface of water to be drawn inward.
● This is why water forms beads on surfaces and also why many insects can walk on water.
● ___________________________________ is an attraction between molecules of
different substances.
● If you’ve ever looked at water in a narrow tube, the surface of the water dips slightly in
the middle.
● This is because the adhesion between the water molecules and _____________________
___ __ _ _ _ _______________________ is stronger than the cohesion between water
molecules.
● Adhesion can also cause water to rise in a narrow tube against the force of gravity.
● That effect is called __________________________________________________ and is
one of the forces that draw water out of the roots of a plant and into its stems and leaves.
● Cohesion is also a part of capillary action, as it holds the column of water together as it
rises.
Solutions and Suspensions
● Water isn’t always pure, but is often found as part of a mixture.
● A _____________________________________ is a material composed of two or more
elements that are physically mixed together but not chemically combined.
● Salt and pepper stirred together is an example of a mixture.
● Living things are in part composed of mixtures involving water.
● Two types of mixtures that can be made with water are
______________________________ and
___________________________________________.
● If a crystal of table salt is placed in a glass of water, sodium and chloride ions on the
surface of the crystal are attracted to the polar water molecules.
● Ions then break away from the crystal and are surrounded by water molecules.
8/17/2015
Miss Kennedy
● The ions gradually become dispersed in the water, forming a type of mixture called a
________________________________________.
● In a saltwater solution, the table salt is the ________________________________, or
substance that is dissolved, and the water is the ________________________________,
or the substance in which the solute dissolves.
● Water’s polarity gives it the ability to dissolve both ionic compounds and other polar
molecules, like sugar, making water the greatest solvent on Earth.
● However, some materials don’t dissolve when placed in water.
● Instead, these materials separate into pieces so small that they don’t settle out, and the
movement of water molecules keeps the small particles suspended.
● The mixtures of water and nondissolved material are known as
___________________________.
● Some of the most important biological fluids are both solutions and suspensions.
● The ________________________ that circulates through your body is mostly water,
which contains many
___________________________________________________________.
● However, blood also contains ________________________ and other
_____________________ __________________________________ that remain in
suspension as the blood moves through the body.
Acids, Bases, and pH
● A water molecule can react to form both positive __________________________ (H+)
and negative ______________________________ (OH-) ions.
● This happens with 1 molecule out of 550 million in pure water.
● Since the numbers of positive hydrogen ions produced is equal to the number of negative
hydroxide ions, water remains neutral.
● With other solutions, this isn’t always the case.
● Chemists devised a measurement system called the
__________________________________ to indicate the concentration of H+ ions in a
solution.
● This scale ranges from 0 to 14, where 7 is a neutral solution.
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Miss Kennedy
● Solutions with a pH below 7 are called ____________________________ because they
have more H+ ions than OH- ions.
● Solutions with a pH above 7 are called ____________________________ because they
have more OH- ions than H+ ions.
● Each step on the pH scale represents a factor of __________.
● For example, a liter of solution with a pH of 4 has 10 times as many H+ ions as a liter of
solution with a pH of 5.
● An ________________________ is any compound that forms H+ ions in a solutions.
● Acidic solutions contain higher concentrations of H+ ions than pure water and have pH
values below 7.
● Strong acids, like hydrochloric acid, have pH values that range from
______________________.
● A ___________________ is a compound that produces hydroxide (OH-) ions in solution.
● Basic, or ________________________________, solutions contain lower concentrations
of H+ ions than pure water and have pH values above 7.
● Strong bases, such as lye, tend to have pH values ranging from
__________________________.
● If the pH in the human body goes lower than 6.5 or higher than 7.5, it will affect the
chemical reactions that take place within the cells.
● Therefore, controlling pH is important for maintaining homeostasis.
● One of the ways that the body controls pH is through dissolved compounds called
________________________________.
● Buffers are ____________________ acids or bases that can react with
____________________ acids or bases to prevent sharp, sudden changes in pH.