Transcript Properties of Water PP

Properties of Water
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Two Types of Covalent Bonds
There are two types of covalent bonds:
1.) polar covalent
2.) non-polar covalent bonds
What is the difference?
1.) Water is a polar molecule and has a
very unique structure
Polar covalent bonds = the unequal sharing of
electrons
Polar covalent bonds have a region of slight positive
charge and a region of slight negative charge.
**Atoms in polar
covalent bonds
share electrons
unequally
Hydrogen bonds
• Opposite charges of polar molecules can
interact to form hydrogen bonds.
• A hydrogen bond is an attraction between a
slightly positive and a slightly negative atom,
(often oxygen)
Non-Polar Covalent Bonds
• Atoms in non-polar covalent bonds share their
electrons evenly
2.) Water is the universal solvent
SALT
• Solute = a substance that dissolves
in a solvent
• Solvent = the substance that dissolves
another substance (solute)
WATER
• Solution = a mixture of substances that is the same
SALT WATER
throughout – (it is homogeneous)
Practice
Ice tea
• Which is the solute??
• Which is the solvent?
Answers
Ice Tea
Water is the solvent
Tea and sugar are the solutes (what is being
dissolved)
3.) Water has the properties of
adhesion and cohesion
• Cohesion- the attraction between molecules of the
same substance
– Water is attracted to other molecules because of polar
properties (hydrogen bonding!)
– Water molecules are clinging to each other
• As a result of cohesion:
– We have Surface tension = water is pulled together creating
the smallest surface possible
• Examples of cohesion: tear drop,
rain drop, drop of water coming
from the faucet
3.) Water has the properties of
adhesion and cohesion
• Adhesion- attraction of molecules of different
substances Water molecules stick to other
things
How do plants get water absorbed in
their roots to the rest of the plant?
4.) Water is important for capillary
action
• Because of water’s adhesive and cohesive
properties water can be transported from the
roots to the top of the plant = capillary action
• How can you explain this…
• Think water in a straw… water moves through
plants in a similar way
• Water is attracted to the walls of the tube, and
the water molecules are attracted to each other
5.) Water is less dense as a solid than a
liquid
• Why??
– Why can ice (water’s solid form) float on liquid
water?
ICE
LIQUID
• This is because the hydrogen bonds are stable in ice
– each molecule of water is bound to four of its
neighbors
– When water is frozen, the hydrogen bonds keep
molecules at “arms length” far enough a part to make
ice just dense enough to float on the liquid surface
– Solid – Water molecules are bonded together – space
between is fixed (not changing)
– Liquid – Water molecules are constantly breaking,
bonding and re-bonding – space is always changing
6.) Water has a strong surface tension
• The cohesive property of water (water molecules
attracting to other water molecules) gives it a high
surface tension
– Surface tension – the stickiness of water molecules of
the surface of water
– Due to the attraction of water
molecules to each other
• Enables a paper clip to float,
small insects on water, etc.
5 properties of water
1.) Water is a polar molecule
2.) Water is the universal solvent
3.) Water has the properties of adhesion and
cohesion
4.) Water is less dense as a solid than a liquid
5.) Water is important for capillary action
6.) Water has strong surface tension
Concept Map
• Create a concept map. Include ALL of the following
terms in your concept map. Provide examples,
draw pictures, include ANYTHING that will help
you to make connections and remember the
material!
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Polar
Solute
Molecule
Hydrogen bond
Hydrogen atom
Oxygen atom
Electrons
Universal solvent
- solution
-surface tension
-solvent -properties of water
- adhesion -covalent bonds
- cohesion -nonpolar
- capillary action
- dense
-solid
-liquid