Jigsaw
Properties of Water
Polarity
Polarity simply means that a molecule has both a positively and a
negatively charged end. One important property of water is that it is
composed of these polar molecules (molecules that have a positive
charge on one end and a negative charge on the other). Water has a
simple molecular structure; it is composed of one oxygen atom and two
hydrogen atoms (its chemical formula is H2O). The two hydrogen atoms
and one oxygen atom within a water molecule form covalent bonds,
meaning they share electrons. While there is no net charge to a water
molecule, the polarity of water creates a slightly positive charge on the
hydrogen side and a slightly negative charge on the oxygen side; this
contributes to water's properties of attraction.
As a result of water's polarity, each water molecule attracts
other water molecules because of the opposite charges between
them, forming hydrogen bonds. Water also attracts, or is attracted
to, other polar molecules such as sugars, salts, and acids.
Universal Solvent
A solvent is any substance, typically a liquid, which is used to dissolve another, different
substance. Water is capable of dissolving a variety of different substances, which is why it is such a good
solvent. In fact, water is called the "universal solvent" because it dissolves more substances than any
other liquid. This is important to every living thing on earth. It means that wherever water goes, either
through the air, the ground, or through our bodies, it takes along valuable chemicals, minerals, and
nutrients.
It is water's chemical composition and physical attributes that make it such an excellent solvent.
Water molecules have a polar arrangement of oxygen and hydrogen atoms—one side (hydrogen) has a
partial positive electrical charge and the other side (oxygen) has a partial negative charge. This allows
the water molecule to become attracted to many other different types of molecules. Water can become
so heavily attracted to a different compound, like salt (NaCl), that it can disrupt the attractive forces that
hold the sodium and chloride in the salt compound together, thus dissolving it.
Jigsaw
Properties of Water
Density
Density is a characteristic property of a substance. The density of a substance is the relationship
between the mass of the substance and how much space it takes up (volume). The mass of atoms, their
size, and how they are arranged determine the density of a substance. The more mass an object
contains in a given space, the more dense it is. Mathematically, you can determine the density of an
𝑚𝑎𝑠𝑠
𝑀
object by using the formula 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 =
or 𝐷 = .
𝑣𝑜𝑙𝑢𝑚𝑒
𝑉
Water can exist as a gas (water vapor), liquid, or solid (ice). In liquid form, water has a density of
1 g/mL (1 gram per milliliter), and it is used as a way to measure the density of other objects. However,
the density of water depends on its temperature. The density of most substances increases when a
liquid becomes a solid, so the solid form of most substances is denser than the liquid form; thus, a block
of most solids will sink in the liquid. However, a block of ice floats in liquid water because ice
is less dense. Solid water (colder temperature) is actually less dense than liquid water (warmer
temperature) because the molecules in ice are spread farther apart than those in water.
Buoyancy
Have you ever wondered why massive boats and ships weighing hundreds of tons float while
small objects like rocks sink? Have you ever wondered why when you inhale in a pool you float and
when you exhale you sink to the bottom even though you weigh the same? This phenomenon can be
explained by the scientific principle called buoyancy. Buoyancy is the upward force that an object feels
from a fluid, like water. When compared to the weight of the object, buoyancy is what makes an object
float, sink, or remain neutrally buoyant in the water.
When an object is placed in water, it displaces an
amount of water equal to its own volume. Volume is the
amount of space something takes up. Whether the object
floats or not depends on its density, or how much mass it
has, compared to the density of water. Objects that are
denser than water sink. Objects that are less dense than
water float.
When an object floats, the upward buoyant force
exerted by the water (or other liquid) is greater than the
downward force of gravity acting on the object. If an object’s
density is less than water’s density (1 g/cm³), it will float.
When an object sinks, the weight of the object is greater
than the upward buoyant force exerted by the water and its
density is greater than 1 g/cm³. When an object is neutrally
buoyant, meaning it neither sinks nor floats, then the weight
of the object is equal to the upward buoyant force exerted
by the water.
Jigsaw
Properties of Water
Specific Heat
When was the last time you sat down and thought about what your life would be like if water
did not have such a high specific heat capacity? Probably never, right?
Lucky for you and me, water does indeed have a very high specific heat capacity. The specific
heat of water is the amount of heat needed to raise 1 gram of water by 1° Celsius. One of water’s most
significant properties is that it takes a lot of heat to it to make it get hot.
Metals have a much lower specific heat capacity than water. If you've ever held onto a needle
and put the other end in a flame (don’t try that at home!) you know how fast the needle gets hot, and
how fast the heat is moved through the length of the needle. Not so with water.
The high specific heat capacity of water has a great deal to do with regulating extremes in the
environment. The heat capacity of the water means the temperature of bodies of water will stay
relatively the same from day to night. Oceans and lakes help regulate the temperature ranges that
billions of people experience in their towns and cities. Water surrounding or near cities take longer to
heat up and longer to cool down than do land masses, so cities near the oceans will tend to have less
change and less extreme temperatures than inland cities. This property of water is one reason why
states on the coast and in the center of the United States can differ so much in temperature patterns. A
Midwest state, such as Nebraska, will have colder winters and hotter summers than Oregon, which has a
higher latitude but has the Pacific Ocean nearby.
Capillary Action
Even if you've never heard of capillary action, it is still important in your life. Capillary action is
important for moving water (and all of the things that are dissolved in it) around. It is defined as the
movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and
surface tension.
Capillary action occurs because water is sticky, thanks to the forces of cohesion (water
molecules like to stay close together) and adhesion (water molecules are attracted and stick to other
substances).
Not only does water tend to stick together in a drop, it sticks to glass, cloth, organic tissues, soil,
and, luckily, to the fibers in a paper towel. Dip a paper towel into a glass of water and the water will
"climb" onto the paper towel. In fact, it will keep going up the towel until the pull of gravity is too much
for it to overcome.
Capillary Action in Action:
 When you spill your glass of BubblyBerryPowerGo (which is, of course, mostly water) on the
kitchen table you rush to get a paper towel to wipe it up. First, you can thank surface tension,
which keeps the liquid in a nice puddle on the table, instead of a thin film of sugary goo that
spreads out onto the floor. When you put the paper towel onto your mess, the liquid adheres
itself to the fibers in the paper towel and the liquid moves to the spaces between and inside of
the fibers.
 Plants and trees couldn't thrive without capillary action. Plants put down roots into the soil
which are capable of carrying water from the soil up into the plant. Water, which contains
dissolved nutrients, gets inside the roots and starts climbing up the plant tissue.
 Capillary action is also essential for the drainage of constantly produced tear fluid from the eye.