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TRANSCRIPT
The Hydrosphere
Chapters 2 – 4
Holt Science
“AHA Question”
Pages 142 – 143
“If water is one of the most common
substances on Earth, what makes it so
unique?”
Page 145
CO: SWBAT identify and describe the
properties of water.
LO: SWBAT compare cohesion and
adhesion.
Imagine
Picture yourself
canoeing down a
gentle stream on a
beautiful sunny
afternoon.
You can see the
gravelly stream
bottom through the
crystal blue water.
All of a sudden, the
silence is broken by
the sound of rushing
water.
You notice that the
current has picked up
and the water is
moving much faster.
What is happening?
In the distance you see
some large boulders
and a waterfall.
Unexpectedly, the
canoe hits a rock and
nearly topples over.
What forces of nature could
cause the stream to
change so drastically?
Essential Questions
What are the properties of water?
How does moving water shape the Earth?
How does erosion and deposition shape
the land?
From where does our drinking water
come?
How do humans impact the water supply?
Brainstorming
What do you know about water?
From where does your drinking water
come?
How do you impact the water supply?
Video Clip
What did you learn?
Water
Covers nearly 70% of Earth’s surface
Most abundant substance on Earth
Most important substance to organisms
Unique properties that help to support life
on Earth
Water Molecules and Polarity
Made up of two hydrogen and one oxygen
Hydrogen shares an electron with oxygen
Oxygen attracts electrons more strongly than
hydrogen
Oxygen pulls the shared electrons closer to its
nucleus
Makes charges unequal, called polarity
Polarity
Causes water molecules to attract each
other
Like weak magnets
Positive pole on hydrogen attracts negative
pole on oxygen
Forms temporary bonds that form and break
easily – called a hydrogen bond
Helps water stick together
Cohesion and Adhesion
Cohesion is the tendency for water
molecules to form weak bonds and stick
together
Surface tension – a force that acts on the
particles at the surface of the liquid
Forms a kind of skin on the water
Water Strider
Jesus Lizard
Adhesion
The tendency of
water to stick to other
substances
Universal Solvent
A solvent is a substance in which another
substance dissolves
Water is called the universal solvent
because it can dissolve more substances
than any other known substance
Due to its polarity
Density
Measure of the mass of a substance per
unit volume
Changes with temperature
Pour cold water into hot water
Cold water sinks to bottom
Changes with change in state
Ice floats in water
Buoyancy
Ability of a fluid to exert an upward force,
called the buoyant force, on an object that
is immersed in the fluid
Property that allows organisms to float
Boats
If metals sink in water, why is a metal
boat able to float?
Boats
It is able to float because its shape
provides areas that can fill with air, which
is less dense than water. The air helps to
lower the density of the entire boat, which,
in turn, allow the buoyant force of the
water to keep the boat afloat.
Specific Heat
The amount of energy needed to raise the
temperature of 1 kg of a substance by 1°C
Specific heat of water --- 4184 J/kg · °C
Allows lakes, streams, and ocean
ecosystems to maintain stable
temperatures
Helps your body to maintain a constant
internal environment
Capillary Action
The tendency of water to rise
Paper towel absorbency
Straw
Review
Which form of water has the highest
density?
A. Ice
B. Warm water
C. Cold water
D. Water vapor
Question 2
How are nutrients transported in water?
A. As compounds
B. As ions
C. As molecules
D. As solids
Question 3
Which of the following describes the
tendency of a water molecule to stick to
other water molecules?
A. Cohesion
B. Density
C. Adhesion
D. Buoyancy
Question 4
The diagram below shows a water
molecule.
Question 4, cont.
What do the charges on either end of the
molecule indicate about the molecule?
A. Water is a polar molecule.
B. Water is a nonpolar molecule.
C. Water is an ionic compound.
D. Water is an ion.