SalinityUnderstanding, Calculating, and Observing

Salinity

Testing the Waters• There are many different types of bodies of water

– Oceans– Lakes– Creeks– Rivers– Ponds– Puddles

• What are some of the similarities and differences between these bodies of water?

• One main difference between different bodies of water is the SALINITY.

What is Salinity?• Salinity is defined as the total

amount of minerals (also known as salts) that are dissolved in water.

• Salts can be made of sodium chloride [NaCl] or other minerals such as potassium [K], calcium [Ca] or magnesium [Mg].

• Salinity is commonly measured in parts per thousand (‰).

Salinity Classification

Body of Water ‰

Red Sea 40

Mediterranean Sea 38

Average Seawater 34.7

Black Sea 18

Baltic Sea 8

Water SalinityFresh Water

Brackish Water

Saline Water

Brine

<.5 ‰ .5-30‰ 30-50‰ >50‰

This table compares the salinities of several different bodies of water

This table shows how water samples with different salinities are classified. Brine has the most salt, with over 50 parts per thousand! That amount of

salt would taste like adding salt instead of sugar to your Kool-Aid!

Salinity and Density• Density = mass/volume or M÷V. • Saltwater has a higher density than

freshwater; – Salt adds more mass to the water

without changing the water’s volume even though the salt dissolved!.

• Saltwater is DENSER than freshwater. This allows objects to float much easier.

• Salinity is also affected by temperature. The warmer saltwater becomes, the more its volume increases, which lowers the density (thermal expansion). As water temperature decreases, volume decreases, increasing the density.

Density Demonstration• Questions to ask:• Before Demo:

– What will happen when the eggs are dropped?

• After Demo– In which water sample did the egg float?

• Why?– In which did it sink?

• Why?

The Dead Sea• The salt content of water affects the

distribution of animal and plant species according to the amount of salinity they can tolerate. Many species can survive

only within certain salinity levels. Changes in salinity can have a

detrimental effect on organisms.• Also called the Salt Sea, the Dead Sea is a

salt lake bordering Jordan to the east, and Israel and the West Bank to the west.

• The Dead Sea is 378 m (1,240 ft) deep, the deepest hyper saline lake in the

world. It is also one of the world's saltiest bodies of water. It is 8.6 times more salty

than the ocean. • This salinity makes for a harsh environment where animals cannot

flourish, hence its name.

The water in the Dead Sea is so dense that it

makes floating essentially

effortless for swimmers. They can even sit back

and read the newspaper.

Calculating Salinity• Salinity may be calculated by measuring the

specific gravity of a sample of water using a hydrometer.

• The greater the salinity, the higher the hydrometer will float.

• Salinity can also be calculated with a chemical titration (chemical rxn), evaporation, conductivity meter (passes electricity through a sample measuring the speed), or with a refractometer (based on light bending from dissolved salts).

Conductivity meter

Titration

Refractometer

Hydrometer