Chapter 3 Flashcards
Water is the only common substance on Earth to … Furthermore, the solid form of water …
exist in the natural environment in
all three physical states of matter.
floats on the
liquid form, a rare property emerging from the chemistry of the water molecule.
. In the Arctic, warmer waters and the smaller ice pack are resulting
in blooms of
phytoplankton (microscopic aquatic photosynthetic organisms), seen
from space as the “cloudy” seawater in
. Organisms that depend on Arctic
ice, however, are suffering. For instance,
a population of black guillemots in Alaska is
declining due to the warming climate and reduction of Arctic sea ice.
what ability of water makes it cool
the structure of a water molecule allows it to
interact with other molecules, including other water molecules n hydrgrogen bonding ofcccc
polar covalent bonds and polarity of water
; these are polar covalent bonds (see Figure 2.11).
This unequal sharing of electrons and water’s V-like shape
make it a polar molecule, meaning that its overall charge
is unevenly distributed. In water, the oxygen of the molecule
has two regions of partial negative charge (δ-), and each
hydrogen has a partial positive charge (δ+).
where do the properties of water come from in terms of attractions
The properties of water arise from attractions between oppositely charged atoms of different water molecules: The partially
positive hydrogen of one molecule is attracted to the partially
negative oxygen of a nearby molecule. The two molecules are
thus held together by a hydrogen bond
what happens with hydrogen bonds in water
When
water is in its liquid form, its hydrogen bonds are very fragile,
each only about 1/20 as strong as a covalent bond. The hydrogen bonds form, break, and re-form with great frequency. Each
lasts only a few trillionths of a second, but the molecules are
constantly forming new hydrogen bonds with a succession of
partners. Therefore, at any instant, most of the water molecules are hydrogen-bonded to their neighbors
the properties of water emerge from
s. The extraordinary
properties of water emerge from this hydrogen bonding, which
organizes water molecules into a higher level of structural order.
cohesion
. Collectively, the hydrogen bonds hold
the substance together, a phenomenon called cohesion.
importance of cohesion
Cohesion due to hydrogen bonding contributes to the
transport of water and dissolved nutrients against gravity in
plants. Water from the roots reaches the leaves through a network of water-conducting cells (Figure 3.3). As water evaporates from a leaf, hydrogen bonds cause water molecules
leaving the veins to tug on molecules farther down, and the
upward pull is transmitted through the water-conducting
cells all the way to the roots
adhesion and importance
Adhesion, the clinging of one
substance to another, also plays a role. Adhesion of water by
hydrogen bonds to the molecules of cell walls helps counter
the downward pull of gravity
suface tension d and what is it related t
Related to cohesion is surface tension, a measure of how
difficult it is to stretch or break the surface of a liquid.
arangement of water and air at the surface of a liquid and its significance
At the
interface between water and air is an ordered arrangement of
water molecules, hydrogen-bonded to one another and to the
water below, but not to the air above. This asymmetry gives water an unusually high surface tension, making it behave as
though it were coated with an invisible film. You can observe
the surface tension of water by slightly overfilling a drinking glass; the water will stand above the rim
how do hydrogen bonds relate to surface tension
. The high surface tension
of water, resulting from the
collective strength of its hydrogen
bonds
kinetic energy
Anything that moves has kinetic energy, the energy of
motion. Atoms and molecules have kinetic energy because
they are always moving, although not necessarily in any particular direction
thermal energy
The faster a molecule moves, the greater its
kinetic energy. The kinetic energy associated with the random
movement of atoms or molecules is called thermal energy.
temp v thermal energy
. Temperature represents the average kinetic energy
of the molecules in a body of matter, regardless of volume,
whereas the thermal energy of a body of matter reflects the
total kinetic energy, and thus depends on the matter’s volume.
swimming pool and coffee pot- which has more temp n which has more thermal en
e. Note, however, that although
the pot of coffee has a much higher temperature than, say, the
water in a swimming pool, the swimming pool contains more
thermal energy because of its much greater volume.
Whenever two objects of different temperature are b
how does ice cool a drink
Molecules in
the cooler object speed up at the expense of the thermal energy
of the warmer object. An ice cube cools a drink not by adding
coldness to the liquid, but by absorbing thermal energy from
the liquid as the ice itself melts
heat
Thermal energy in transfer
from one body of matter to another is defined as heat
calorie
One convenient unit of heat used in this book is the calorie
(cal). A calorie is the amount of heat it takes to raise the temperature of 1 g of water by 1°C. Conversely, a calorie is also the
amount of heat that 1 g of water releases when it cools by 1°C.
kilocal
A kilocalorie (kcal), 1,000 cal, is the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1°C
specific heat
. The specific heat of a substance
is defined as the amount of heat that must be absorbed or lost
for 1 g of that substance to change its temperature by 1°C.
water and temperature change
Water resists changing its temperature; when it does change
its temperature, it absorbs or loses a relatively large quantity
of heat for each degree of change.
