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chemistry of water.pptx
1. A 1.1 - Water
Guiding Questions
● What physical and chemical properties of
water make it essential for life?
● What are the challenges and opportunities
of water as a habitat?
5. Chemistry of a water molecule
Water molecules are polar and hydrogen bonds form between them.
6. Chemistry of a water molecule
Water molecules are polar and hydrogen bonds form between them.
7. Chemistry of a water molecule
Water molecules are polar and hydrogen bonds form between them.
- In a water molecule, there are covalent bonds between oxygen and
hydrogen atoms
- Sharing of electron is unequal → Polar covalent bond
8. Chemistry of a water molecule
Water molecules are polar and hydrogen bonds form between
them.
Positively charged particles and negatively
charged particles attract each other and form
ionic bonds
- Water molecules only partial attraction
between two water molecules → hydrogen
bond
9. Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and
solvent properties of water
12. Adhesion
Hydrogen bonding and dipolarity explain the
cohesive, adhesive, thermal and solvent properties
of water
- Water has the capacity to form intermolecular
associations with molecules that share common
properties
- Because water is polar it will be attracted to other
molecules that are polar or have an ionic charge
Cohesive Properties:
- Cohesion is the ability of like molecules to stick
together
- Water is strongly cohesive (it will form hydrogen
bonds)
13. Adhesion and Cohesion
Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and
solvent properties of water
- Two examples of how living organisms use cohesion
- Conduction of water in xylem and the use of water surfaces as a habitat
14. Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and
solvent properties of water
Adhesion and Cohesion - Conduction of water in xylem
Cohesion allows the transport of water under
tension in plants
- Water is “sucked” upwards from roots to leaves along
the xylem → forms a continuous column of water
- The column of water is “pulled” at both ends
- Root tension → soil particles and water
- Leaves tension → evaporation to the
atmosphere; attraction between cell walls and
water
Water moves up because the pulling forces in the
leaves are greater than those in the soil
16. Use of water surfaces as habitats
Transparency of water is important for aquatic plants to undergo
photosynthesis
17. Use of water surfaces as habitats
Transparency of water is important for aquatic plants to undergo
photosynthesis
18. Use of water surfaces as habitats
Surface tension → elastic membrane
- Water molecules are more attracted to each other than the air
- Surface tension makes it possible for many objects (organisms) to
float on water
19. Use of water surfaces as habitats
Living organisms make use of this property by using water surfaces as
habitats
- Water striders (pond skaters)
- Mosquito larvae
20. Adhesion
Hydrogen bonding and dipolarity explain the
cohesive, adhesive, thermal and solvent
properties of water
- Water has the capacity to form intermolecular
associations with molecules that share
common properties
- Because water is polar it will be attracted to
other molecules that are polar or have an ionic
charge
Adhesive Properties:
- Adhesion is the ability of dissimilar molecules to
stick together
- Water will form intermolecular associations with
polar and charged molecules
21. Adhesion
- Capillary action - water drawn
up a narrow glass tube
Hydrogen bonds can form between water and the surface of a solid
composed of polar molecules → causes water to stick to the surface of a
solid.
22. Adhesion
- Capillary action - water drawn
up a narrow glass tube
Hydrogen bonds can form between water and the surface of a solid
composed of polar molecules → causes water to stick to the surface of a
solid.
Editor's Notes
Water possesses many unique qualities that are essential to maintaining viable living conditions
Approximately 70% of the cell’s internal environment (i.e. cytoplasm) is water-based
It is the only substance occurring naturally in all three states (solid, liquid, gas) on the Earth’s surface
It is required for the anabolic construction of organic molecules (via condensation reactions)
Water is an important medium for metabolic reactions as it is essential to acid-base neutrality and enzyme function
The nucleus of an oxygen atom is more attractive to electrons than the nucleus of a hydrogen atom
Unequal sharing of electron in water molecules gives the hydrogen atoms a partial positive charge and the oxygen atom a partial negative charge
The molecules are bent rather than linear; the two H atoms are on the same side of the molecule and form a pole; the O atom form the opposite pole
Although H bonds is a weak intermolecular force, water molecules are small and so there are many of them per unit volume of water
There are also a large number of H bonds which collectively give water its unique properties.
Water is less dense as a solid than as a liquid (max density ~4C)
Ice floats on water
Prevents oceans from freezing as ice layer prevents exposure to cold temperatures
Like will always dissolve like
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients
Xylem is made up of tissues whose cells are dead at maturity
All liquids have surface tension but only a few (such as mercury) have stronger surface tension than water.
To break urface tension many hydrogen bonds must be broken simultaneously
All liquids have surface tension but only a few (such as mercury) have stronger surface tension than water.
To break surface tension many hydrogen bonds must be broken simultaneously
Water is attracted to many chemical substances in soil
If soil is porous, water is drawn by capillary action through dry soil.
This is how water can rise up from an underground source, even through gravity tends to pull it down.
