Chemical and Physical Features of

SeawaterChapter 3

Figure 3.01

The charged ends of the water molecule (hydrogen bonds) gives it unique properties.

• Water is cohesive, it sticks together.

• Water is adhesive, it sticks to other things.

• It expands when it freezes.

• Water is the universal solvent, it dissolves most solids.

Water molecules

Figure 3.02

Evaporation occurs when molecules break free of hydrogen bonds and enters the gaseous state.

Figure 3.03

Water molecules are spaced further apart when frozen, making it less dense than liquid water. Why is that important

to a Marine Biologist?

WATER PHASES

Figure 3.05

Water the universal solvent weakens the bonds of the sodium chloride, causing it to dissociate.

Figure 3.06

Ions enter the ocean via weathering of rock and volcanic activity.

Solutes in seawater

Sodium and chlorine account for 85% of the solutes in seawater.

• Salinity is defined as the amount of salt dissolved in water. Salinity is expressed as the number of grams of salt left when 1,000 grams of sea water is evaporated. If 35 grams of salt remains and 965 grams of water evaporated, the salinity would be 35 parts per thousand, or 35 0/00. Sea water is about 3.5 percent salt. Most marine organisms die in fresh water.

• When salt water freezes the ions are not included in the ice. consequently the surrounding water increases in salinity and the ice is all most pure water. Salt water freezes at a colder temperature than pure water.

Figure 3.07

This Niskin bottle is used to sample water at various depths

Figure 3.08

Thermocline is where the temperature drops rapidly as it gets deeper.

Figure 3.09a

Many collection bottles can be arranged along with other instruments and lowered by cable. Temperature, salinity, light,

water clarity, and other data can be collected.

Figure 3.09b

Figure 3.11

Different colors of light penetrate to different depths in the ocean.

Figure 3.12

Red colors are filtered out first.

Figure 3.13

The secchi disk is a simple device used to detect water clarity.

Figure 3.14

At sea level there is 1 ATM atmosphere (14.7 psi). With each 10m or 33ft of depth another ATM of pressure is added.

Figure 3.15

This fish was brought up to fast from depth, and the swim bladder expanded filling with air.

Figure 3.10

Satellite image shows ocean temperatures coldest is blue and warmest in red. Why is it warmer in the middle?