• http://vimeo.com/37064053

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

• 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)

• Atoms in non-polar covalent bonds share their electrons evenly

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 throughout – (it is homogeneous) SALT WATER

Ice tea
• Which is the solute??
• Which is the solvent?

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.

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

• 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!
– Polar
– Solute
– Molecule
– Hydrogen bond
– Hydrogen atom
- solution -surface tension
-solvent -properties of water
- adhesion
- cohesion
-covalent bonds
-nonpolar
- capillary action
– Oxygen atom
– Electrons
- dense
-solid
– Universal solvent -liquid