Anomalous Expansion of water.docx - Diana B. Buis BSED 2A...

Diana B. Buis
BSED 2A
SCI 157 THERMODYNAMICS
ANOMALOUS EXPANSION OF WATER
Anomalous expansion of water is an abnormal property of water whereby it
expands instead of contracting when the temperature goes from 4°C to 0°C,
and it becomes less dense. The density becomes less as it freezes because
molecules of water normally form open crystal structures when in solid form.
Water is denser than ice while almost all the other substances are denser in
solid form than in liquid form.
Normally, liquids contract on cooling & the density increases. However,
water is special. It contracts when cooled, down to a temperature of 4°C but
thereafter begins to expand as it reaches 0°C and turns into ice. Water attains
its maximum density at 4°C. This is caused by the hydrogen bonding between
the oxygen atoms that are negatively charged and the hydrogen atoms that are
positively charged, from two different molecules of water. The density of ice is
lower, and so it floats on water
SCIENTIFIC REASON
Anomalous expansion of water takes place because when water is heated to
277K hydrogen bonds are formed. Though ice is supposed to expand when it