The Extraordinary Properties of
Water
Water
• A water molecule (H2O),
– one oxygen and two hydrogen.
•Boils at 100 °C
•Freezes at 0 °C
H
O
H
Hydrogen Bonds
• Formed between a polar
molecule and a Hydrogen
atom.
• One hydrogen bond is weak,
but many are strong.
Cohesion
•Attraction between particles of the
same substance.
o Water likes water!
•Causes
o Surface tension – a measure of the
strength of water’s surface (think
water striders!)
o cohesion
Adhesion
•Attraction between two different
substances.
o Condensation – on your
window or coke can.
o Dew on a leaf
Capillary Action
• Water molecules will “tow” each
other along in a thin tube
oRedwood trees…SOOOOO tall! How
do they get water all the way to the
top?!
oPaper towels soak up water
Water is Less Dense as a Solid
•Ice is less dense as a solid than as a
liquid.
•Air gets caught in between hydrogen
bonds and forms crystal-like structure.
•So ice floats!
Water is Less Dense as a Solid
•Which is ice and which is water?
Water is Less Dense as a Solid
Water
Ice
Water’s Importance
• Universal solvent
• Good coolant
• Floating ice protects living organisms
against temperature extremes.