Page 33 - (DK) Ocean - The Definitive Visual Guide

THE PROPERTIES OF WATER 31

LAND AND SEA Heat Capacity
Water’s high heat capacity
means that the Sun warms A second property of liquid water that can be attributed to hydrogen
the sea more slowly than land.
In this satellite-generated bonding is its unusually high heat capacity, which exceeds that of nearly
temperature map of south all other known liquids (see table, left). When heat is added to water,
California during a heat wave, most of the heat is used to break hydrogen bonds linking the molecules.
much of the land (red) is 122ºF Only a fraction of the energy increases the vibrations of the water
(50ºC) or more, but the sea (left) molecules, which are detected as a rise in temperature. This means that
is cool, at 50ºF (10ºC).
areas of ocean can absorb and release huge amounts of heat energy with
little change in temperature. It also means that movements of water—
SPECIFIC HEAT CAPACITY ocean currents—transfer enormous
amounts of heat energy around the
Specific heat capacity (SHC) is the energy (in joules) needed to raise the
temperature of 1 gram of a substance by 1ºC. Listed below are the SHCs planet. This role of ocean currents is
of 13 liquids, measured at room temperature unless otherwise stated. vital to Earth’s climate (see p.66).
SUBSTANCE JOULES/GRAM ºC
Liquid ammonia at –40ºF (–40ºC) 4.7
Fresh water 4.19 HEAT ON THE MOVE
In this temperature map
Seawater at 35ºF (2ºC) 3.93
of part of the northwest
Glycerin 2.43
Atlantic, the water surface
Ethanol (ethyl alcohol) 2.4 ranges from about 41ºF (5oC)
Acetone 2.15 (blue) to 77ºF (25ºC) (red).
A warm current, the Gulf
Kerosene 2.01
Stream is visible in red.
Olive oil 1.97
Benzene 1.8
Turpentine 1.72
Freon 12 refrigerant at -40ºF (-40ºC) 0.88
Bromine 0.47
Mercury 0.14

WATER TWISTER
The effects of surface tension can cause moving
sheets, jets, and streams of water to assume or
hold together in some surprising forms, as in this
slightly spiral-shaped water jet.

Three States of Water
The temperatures at which water changes between its three states—
melting point (ice to liquid water) and boiling point (liquid water to
water vapor)—are both high compared with substances having similarly
sized molecules. For ice to melt and water to vaporize, high levels of
energy are needed to break all the hydrogen bonds. Water is also unusual
in that its solid form is slightly less dense than its liquid form, so ice
floats in liquid water. The reason for this is that the molecules in ice
are loosely packed, whereas those in liquid water move around in snugly
packed groups. The fact that ice floats on liquid water is important
because it allows the existence of large areas of polar sea ice (see pp.
198–199). These affect heat flow between ocean and atmosphere
and help stabilize ocean temperatures and Earth’s climate.

SIDE BY SIDE
Water is the only natural INTRODUCTION
SOLID, LIQUID, AND GAS substance found in all three
In ice, hydrogen bonds hold the water states at Earth’s surface.
ICE LIQUID WATER WATER VAPOR molecules together in a rigid structure. In Sometimes, ice, liquid water,
Hexagonal Small clumps Widely spaced liquid water, the bonds hold the molecules and condensing water vapor
crystal of bonded unbonded in small, moving clumps. In water vapor, can be seen side by side, as
lattice molecules molecules there are no hydrogen bonds. here at the fjord in Spitsbergen.