water – chapter 11. properties of water polar molecule cohesion and adhesion high specific heat...
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Water – Chapter 11
Properties of Water• Polar molecule• Cohesion and
adhesion• High specific heat• Density – greatest
at 4oC• Universal solvent of
life
Polarity of Water
• In a water molecule two hydrogen atoms form bonds with an oxygen atom. This gives water a positive side and a negative side like a magnet.– the part around oxygen has a partial negative charge.
–The part near the two hydrogen atoms has a partial positive charge.
Polarity of Water
•We say water is a POLAR molecule because it has a positive pole and a negative pole (like north and south poles)
•Cool Properties of Water
•Cool Properties of Water– Water’s “polar-ity” makes it sticky
Living things Depend on Water’s “stickiness”
• In plants, water can move against gravity.
• It helps move chemicals around inside your body.
• Water has a high “Surface tension”
–Water behaves as if covered by an invisible film.
– Some animals can stand, walk, or run on water without breaking the surface!
•Cool Properties of Water
– Water’s “polar-ity” makes it sticky
– Resists changes in temperature
So, water can absorb or release lots of heat with only a little change in its own temperature. It acts like a heat battery.
Degrees Celsius at Sea Level
100oC Water boils
37oC Human body temperature
23oC Room temperature
0oC Water freezes
What does altitude have to do with boiling & freezing?
The higher you are, the lower the air pressure is, so water molecules want to fly around.
•Cool Properties of Water– Water’s “polar-ity” makes it sticky
– Resists changes in temperature
– Takes a lot of heat to turn it into a vapor
•Cool Properties of Water– Water’s “polar-ity” makes it sticky
– Resists changes in temperature
– Takes a lot of heat to turn it into a vapor
– Expands when it freezes
So, ice floats!
•Cool Properties of Water– Water’s “polar-ity” makes it sticky
– Resists changes in temperature
– Takes a lot of heat to turn it into a vapor
– Expands when it freezes
– Lots of things can dissolve in it
Chapter 11, page 362
1. 71% of Earth’s surface is covered by water.
Chapter 11, page 362
1. 71% of Earth’s surface is covered by water.
2. 97% of Earth’s water is salt water.
Chapter 11, page 362
1. 71% of Earth’s surface is covered by water.
2. 97% of Earth’s water is salt water.3. 70% of freshwater is frozen.
Chapter 11, page 362
1. 71% of Earth’s surface is covered by water.
2. 97% of Earth’s water is salt water.3. 70% of freshwater is frozen.4. Your body is 2/3 water.
Page 365
The Water Cycle: page 365
The Water Cycle: page 365
1. Evaporation: Heat causes water molecules to spread out into a vapor.
When salt water evaporates, the salt is left behind (making fresh water vapor).
The Water Cycle: page 365
1. Evaporation: Heat causes water molecules to spread out into a vapor.
2. Condensation: As air cools, water molecules slow down and stick together.
The Water Cycle: page 365
1. Evaporation: Heat causes water molecules to spread out into a vapor.
2. Condensation: As air cools, water molecules slow down and stick together.
3. Precipitation: When enough water molecules stick together, they fall to the ground
The Water Cycle: page 365
1. Evaporation: Heat causes water molecules to spread out into a vapor.
2. Condensation: As air cools, water molecules slow down and stick together.
3. Precipitation: When enough water molecules stick together, they fall to the ground
Three-fourths of the earth is covered by water. The water serves as a large heat sink responsible for:
1. Prevention of temperature fluctuations that are outside the range suitable for life.
2. Coastal areas having a mild climate
3. A stable marine environment
Specific Heat is the amount of heat that must be absorbed or lost for one gram of a substance to
change its temperature by 1oC.
Evaporative Cooling• The cooling of a
surface occurs when the liquid evaporates
• This is responsible for:– Moderating earth’s
climate
– Stabilizes temperature in aquatic ecosystems
– Preventing organisms from overheating
Density of Water• Most dense at 4oC• Contracts until 4oC• Expands from 4oC to
0oC
The density of water:
1. Prevents water from freezing from the bottom up.
2. Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation.
3. Makes transition between season less abrupt.
– When water reaches 0oC, water becomes locked into a crystalline lattice with each molecule bonded to to the maximum of four partners.
– As ice starts to melt, some of the hydrogen bonds break and some water molecules can slip closer together than they can while in the ice state.
– Ice is about 10% less dense than water at 4oC.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 3.5
Solvent for Life• Many chemicals can dissolve in water.• Chemistry of life happens in water.