WATER

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WATER

• When you look at water, taste water and smell
  water - well, what could be more boring?

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Boring Water!

• Colorless
• No taste
• No smell
• Its the hidden qualities of water that make it
• an interesting subject to learn about
• So get excited!

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Properties of Water

• Structure of the Water Molecule
• Polarity
• Cohesion
• Adhesion
• Universal Solvent
• Density
• Buoyancy
• Specific Heat

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Water Basics

• Freezing Point
• Fahrenheit
• Celcius
• Boiling Point
• Fahrenheit
• Celcius

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Water Basics

• Freezing Point
• Fahrenheit 32 degrees
• Celcius 0 degrees
• Boiling Point
• Fahrenheit 212 degrees
• Celcius 100 degrees

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Three States of Matter
Water is the only natural substance that can
exist in all three states of matter!
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The Water Molecule H20

• 1 oxygen atom
• 2 hydrogen atoms
• This arrangement
• makes it possible for
• water to have properties
• unlike any other
• substance on Earth!

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Polarity

• The hydrogen side of the water molecule has a
  slight positive charge
• On the oxygen side of the molecule a negative
  charge exists.
• Water molecules are attracted to each other
  because of their shape and these
• opposite charges.
• These opposite charges make water
• a polar molecule
• The earth has two poles at opposite ends
• The water molecule has two poles as well

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See how they line up?
Hydrogen Oxygen
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Cohesion

• The force that holds molecules of a single
  material together
• All of the attraction between water molecules
  makes them clump together
• We call these clumps drops

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Adhesion

• Because of their shape, water molecules are
  attracted to other substances too
• like you
• or this leaf
• This is why there are drops of water on your skin
  when you get out of the pool
• The drops can stick to a vertical structure
  despite the force of gravity pulling them down

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Cohesion Adhesion

• These forces work together to form drops of water
  on your skin or a leaf.
• Water sticks to something because of adhesion.
• Water forms drops because of cohesion.
• It is not in a thin film all over your body

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Drops on a Penny

• Cohesion
• The force that held the water molecules together
• Surface Tension
• Surface of any liquid acts like a thin, elastic
  film
• Molecules near the surface are attracted to the
  rest of the liquid

Drop of Water on Penny
Penny
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Adhesion Capillary Action

• Adhesion is responsible for capillary action
• Water and its dissolved substances move through
  the roots of plants and the tiny blood vessels in
  our bodies.
• Also allows groundwater to move from wet areas of
  an aquifer to dry areas

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Ex Capillary Action

• Paper Towel
• Sponge
• Absorb liquid through capillary action allowing a
  fluid to be transferred from a surface to the
  sponge or towel.
• The small pores of a act as capillaries, causing
  them to absorb a comparatively large amount of
  fluid

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Water is called the Universal Solvent

• WHY?
• Water dissolves more substances than any other
  liquid on Earth!
• Wherever water goes it
• takes along valuable
• chemicals, minerals,
• and nutrients.
• Like in the ground
• or in our bodies

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Why is this important?

• Pretty much every substance that we know about
  has been found dissolved in Earth's waters at one
  point in time.
• ?Salt ?Alcohol
• ?Sugar ?Corn Syrup
• ?Minerals
• Waters ability to act as the universal solvent
  allows for life on Earth.
• Without it life could not exist because water
  transfers nutrients vital to life in both animals
  and plants.

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Rain Water

• A drop of rain water falling through the air
  dissolves atmospheric gases.
• When rain reaches the earth, it affects the
  quality of the land, lakes, and rivers
• Bad.think of air pollution that is transferred
  into our water by rain
• Goodthink about pollen that is removed or
  cleaned from the air when it rains

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Ever heard of hard water?

• Water's has so many things dissolved in it that
  the water we use is rarely pure.
• It usually has several minerals dissolved in it.
• The presence of these minerals is the difference
  between hard water and soft water.
• Hard water is not dangerous. It just contains a
  lot of calcium and magnesium, but may also
  contain metals.
• Soap will not lather well in hard water
• It can cause Lime scale deposits in pipes,
  water heaters and toilets, spots on your dishes,
  and build up on tiles in your shower

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Water Softeners

• Many of you probably have a softener hooked up to
  your water supply at home.
• This way you prevent spots or your dishes and it
  feels better on your skin.

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Specific Heat

• The specific heat of water is the amount of
  energy required to raise the temp. of 1 gram of
  water by 1º Celsius.
• This means that water can absorb a lot of heat
  before it begins to get hot.
• It also means that it takes a long time for some
  materials with water in them to cool down Apple
  Pie vs. Aluminum Foil
• Water is valuable to industries and your car's
  radiator as a coolant.

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Water has a high specific heat when compared with
other common substances... especially metals.
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Main Idea

• The higher the specific heat of a substance, the
  more energy it takes to increase its temperature.
• Water has a high specific heat.
• It takes a lot of energy to make water warm up!

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Specific Heat

• In other words, it takes a lot of
• energy to change the temperature
• of water.
• This resistance to abrupt changes in temperature
  protects aquatic organisms from harsh temperature
  extremes.
• It also means that water is often at a very
  different temperature than the surrounding air
  think about our ocean water in the winter time.
• It also helps regulate the rate at which air
  changes temperature.
• The temperature change between seasons is gradual
  rather than sudden, especially near the oceans.

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What is the relevance of waters high specific
heat to life on Earth?

• By warming up only a few degrees, a large body of
  water can absorb and store a huge amount of heat
  from the sun during the day especially in the
  summer.
• At night and during winter, the gradual cooling
  water can warm the air around it.
• Coastal areas generally have milder climates than
  inland regions.
• Because organisms are made primarily of water,
  they are more able to resist changes in their own
  temperatures than if they were made of a liquid
  with a lower specific heat.

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Density

• Density is the mass of an object divided by its
  volume (D m/v)
• Units kilograms per cubic meter (kg/m³)
• grams per cubic meter (g/cm³)
• Density of water is 0.997 g/cm³
• Density explains why some things float and others
  sink in water
• A rock at the bottom of a stream is denser than
  the water
• It has a greater mass per unit volume so it sinks
  
• A wooden stick is less dense than the water, so
  it floats
• Water is unique in that its solid form (ICE)
• is less dense than its liquid form.
• So ice floats.

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Ice

• If ice sank, then eventually all ponds, lakes,
  and even the oceans would freeze solid,
• This would make life as we know it impossible
• During summer, only the upper few inches of the
  ocean would thaw.
• Instead, when a deep body of water cools, the
  floating ice insulates the liquid water below,
  preventing it from freezing and allowing life to
  exist under the frozen surface.

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Salt Water vs. Fresh Water

• Dissolving a substance in water can increase its
  density.
• Example
• Salt water is denser than fresh water because
  of the dissolved salt. This increases the upward
  buoyant force that exerted on an object in salt
  water. An object will float better in salt water
  than it will in fresh water.

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Floating in the Dead Sea
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Buoyancy

• Less dense materials float in more dense
  materials because of buoyancy
• Buoyancy is the upward force that keeps things
  afloat.
• An object placed in water has 2 forces acting
  upon it
• Downward force is exerted on the object by
  gravity
• Upward force occurs because the pressure inside a
  body of water increases as water gets deeper
• An object will float when the upward force on
  the bottom of the object is more than the
  downward force on the top of the object
• Simply, when placed in water, an object will
  float if its buoyancy is greater than its weight.
  And it will sink if its weight is greater than
  its buoyancy.

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Buoyancy

• When you place a block of wood in a pail of water
  the block displaces some of the water, and the
  water level goes up
• If you could mass the water that the wood
  displaces, you would find that its mass equals
  the mass of the wood.
• Blocks of wood that are exactly the same size and
  shape may not displace the same amount of water.
• EX A block of wood made of oak sits deeper in
  the water (and therefore displaces more of the
  water) than does a block of pine.
• Why? It's heavier for its size, or
  denser.
• The molecules that make up the oak are more
  closely packed together than the molecules that
  make up the pine.

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Bouyancy

• If you could somehow keep increasing the density
  of a block, it would sink lower and lower into
  the water.
• When its density increased enough to displace an
  amount of water whose mass was equal to the mass
  of the block, it would, in a sense, become
  weightless in the water.
• Making the block just slightly denser would cause
  it to sink to the bottom.

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So what does buoyancy have to do with boats
sinking?

• The space within a boat fills up with water,
  either through the hull or over the boat's sides,
  causing the boat to lose its buoyancy.
• Basically, the added weight of the water causes
  the boat to sink because it weighs more than the
  amount of water it can displace.

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Activity with Density and Buoyancy

• One glass of fresh water
• One glass of salt water
• Compare several objects to see if they float,
• Sink, or flink in either glass.
• Create 2 columns on a piece of paper Fresh
• Water and Salt Water write sink, float or
  flink
• for each object

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Activity Two

• Two beakers (water,alcohol)
• Walk around and kids make observations
• two beakers with clear liquid
• Inference two beakers with water
• Place ice in each, sinks in alcohol
• What can they conclude based on obs. About
  density of this liquid (less than water)
• Guess what it is if they cant get it let one of
  them smell it to see

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Teacher FYI

• We can trace waters high specific heat, like
  many of its other properties, to hydrogen
  bonding. Heat must be absorbed in order to break
  hydrogen bonds, and heat is released when
  hydrogen bonds form. A calorie of heat causes a
  relatively small change in the temperature
  because must of the heat energy is used to
  disrupt hydrogen bonds before the water molecules
  can begin moving faster. And when the
  temperature of water drops slightly, many
  additional hydrogen bonds form, releasing a
  considerable amount of energy in the form of
  heat.
• The ability of ice to float because of the
  expansion of water as it solidifies is an
  important factor in the fitness of the
  environment. If ice sank, then eventually all
  ponds, lakes, and even the oceans would freeze
  solid, making life as we know it impossible on
  Earth. During summer, only the upper few inches
  of the ocean would thaw. Instead, when a deep
  body of water cools, the floating ice insulates
  the liquid water below, preventing it from
  freezing and allowing life to exist under the
  frozen surface.

United Streaming. The Biology of Water Water A
Miraculous Substance The Properties of Water and
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Quiz Practice

• 1.__ The ability to dissolve most substances
• 2.__The amount of energy required to raise the
  temp. of 1 gram of water by 1º Celsius.
• 3.__ The upward force that keeps an object afloat
• 4.__ Water has a positive and a negative end
• 5.__ Causes water to stick to another substance
• 6.__The upward movement of water against gravity
  (occurs in plants)
• 7.__ An objects mass divided by its volume
• 8.__Causes water molecules to be attracted to
  each other and make drops

• A. Buoyancy
• Cohesion
• Density
• Universal Solvent
• Capillary
• Action
• Adhesion
• Specific
• Heat
• Polarity