2. INTRODUCTION
• Water has several other unique physical properties. These
properties are:
1. Water has a high specific heat. Specific heat is the amount of energy
required to change the temperature of a substance. Because water
has a high specific heat, it can absorb large amounts of heat energy
before it begins to get hot.
2. Water conducts heat more easily than any liquid except
mercury. This fact causes large bodies of liquid water like
lakes and oceans to have essentially a uniform vertical
temperature profile.
3. 3. Water molecules exist in liquid form over an important range
of temperature from 0 - 100° Celsius. This range allows water
molecules to exist as a liquid in most places on our planet.
4. Water is a universal solvent.
5. Water has a high surface tension. In other words, water is
adhesive and elastic, and tends to aggregate in drops rather
than spread out over a surface as a thin film. This
phenomenon also causes water to stick to the sides of vertical
structures despite gravity's downward pull.
4. OSMOSIS
• Osmosis is the passage of water from a region of high water
concentration through a semi-permeable membrane to a region of
low water concentration.
• Osmosis , transfer of a liquid solvent through a semi-permeable
membrane that does not allow dissolved solids (solutes) to pass.
6. SURFACE TENSION
• Surface tension is a phenomenon in which the surface of a liquid,
where the liquid is in contact with gas, acts like a thin elastic sheet.
This term is typically used only when the liquid surface is in contact
with gas (such as the air). If the surface is between two liquids (such
as water and oil), it is called "interface tension."
• Water has a greater surface tension than
most other liquids because hydrogen
bonds among surface water molecules
resist stretching or breaking the surface.
• Some animals can stand,walk, or run on
water without breaking the surface.
7. Causes of Surface Tension
• Various intermolecular forces, such as Van der Waals forces, draw the
liquid particles together.
• Surface tension (denoted with the Greek variable
gamma) is defined as the ratio of the surface force F to
the length d along which the force acts:
gamma = F I d
• Units of Surface Tension
• Surface tension is measured in SI units of N/m (newton per
meter), although the more common unit is the cgs unit dyn/cm
(dyne per centimeter).
8. Examples of Surface Tension
• Drops of water.
• Insect walking on water.
• Needle floating on water.
9. water temperature
• Water temperature, of course,expresses how hot or cold the water
is. Technically,heat is an indicator of the kinetic energy of water,or
energy of motion. Increasing temperature indicates increasing
energy, or molecular motion, of water.
• Temperature Measurement Technology –
• Water temperature can be measured with a thermistor, which is a
metallic device that undergoes a predictable change in resistance in
response to temperature changes. This resistance is measured and
converted to a temperature reading in Celsius, Fahrenheit, or Kelvin.
10. Why is water temperature
important?
• Water temperature affects the growth and reproduction
of living organisms. Many animals use temperature as a
signal for when to reproduce and when to migrate.
Generally, animals and plants grow faster at warmer
temperatures, although all organisms have an upper
temperature limit.
• Water temperature has a tremendous impact on water
density. Differences in water temperature and density
cause stratification.
