OCEANOGRAPHY
NAME______________
SEA WATER CHEMISTRY
DATA REPORT
Introduction:
When compared to terrestrial environments, the ocean is a
relatively stable medium in which to live. Temperature and salinity
fluctuate little when compared to temperature and humidity on land.
Dissolved oxygen can vary, and at times in Long Island Sound, the
waters can lose all dissolved oxygen, becoming HYPOXIC. Only
anaerobic organisms can survive. In this investigation you will
investigate how these parameters are measured. Most of the tests
are called FIELD TESTS because they are designed to be performed
in the field.
We will be using the water from our salt water tank(s). Each
station (1-6) is a separate activity, and you can do them in any order
you wish.
SALINITY BY EVAPORATION:
One way to determine the salinity is to evaporate a known
mass of seawater, and determine the mass of “salt” left behind.
Since this takes a day or two, perform this activity first.
Determine the mass of a clean, dry evaporating dish:
MASS OF DRY DISH
_________gm
Mark the dish so you can identify it.
Carefully add some of sea water, and determine the mass of
the dish and the sample.
MASS OF DISH + SAMPLE _________gm
Set the dish aside to evaporate
After evaporation, determine the mass of the dish and the salt:
MASS OF DISH AND SALT _________gm
You now have enough information to determine how much
SEAWATER you started with, and how much SALT you ended up
with:
Work space:
Now you can calculate SALINITY:
MASS OF SALT
SALINITY
=
MASS OF SEAWATER
1000
DATA REPORTS:
STATION 1 - DIRECT DENSITY
MASS OF FLASK + SAMPLE _________gm
MASS OF DRY FLASK
_________gm
MASS OF 100 ml OF SEA WATER ______gm
DENSITY CALCULATION:
STATION 2 - THE HYDROMETER AND T-S-D DIAGRAM
DENSITY FROM HYDROMETER ________gm/ml
TEMPERATURE
________C
SALINITY FROM T-S-D DIAGRAM ________o/oo
STATION 3 – REFRACTOMETER
DENSITY ___________gm/ml
SALINITY ___________o/oo
STATION 4 - SALINITY METER
TEMPERATURE _________C
SALINITY
_________o/oo
STATION 5 - TEST KIT
DISSOLVED OXYGEN ________ppm
STATION 6 – D.O. METER
TEMPERATURE ___________C
DISSOLVED OXYGEN ________ppm
QUESTIONS:
1. What was you lowest density reading?_________ Which method
gave you that reading?
What was your highest density reading?________ Which method
gave you that reading?
Decide which method you think was most accurate and explain
why:
2. What was your highest salinity reading?________Which method
gave you that reading?
What was your lowest salinity reading?________Which method
gave you that reading?
Decide which method was most accurate and explain why:
3. Using your chosen “most accurate” temperature and salinity
readings, determine the solubility of your water sample:
temperature__________c
salinity __________o/oo
solubility _________ppm
How do your dissolved oxygen readings (meter / kit) compare to the
solubility? Is your sample highly oxygenated? Explain:
STATION 1
TO FIND THE DENSITY, WE NEED MASS AND VOLUME.
THE VOLUMETRIC FLASKS AT THIS STATION ARE HAND
CALIBRATED TO EXACTLY 100 ml.
1. FIND THE MASS OF THE EMPTY FLASK
2. ADD EXACTLY 100 ml OF SEAWATER – USE THE
DROPPERS FOR PRECISION – REMEMBER YOUR
MENISCUS:
3. FIND THE MASS OF THE FLASK AND WATER
4. SUBTRACT TO GET THE MASS OF 100 ml OF
SEAWATER
5. DETERMINE THE DENSITY
STATION 2
THE HYDROMETER WILL TELL YOU THE DENSITY OF
THE SAMPLE. FLOAT THE HYDROMETER IN THE WATER,
AND WHEN IT STABILIZES, RECORD THE READING ON
THE NECK WHERE THE WATER LEVEL IS:
USE THE THERMOMETER
TO DETERMINE THE
WATER TEMPERATURE,
AND THE T-S-D DIAGRAM
FOR THE SALINITY.
1.016 g/cc
STATION 3
THE REFRACTOMETER IS AN OPTICAL DEVICE.
PLACE A THIN FILM OF WATER ON THE GLASS, CLOSE
THE COVER, AND VIEW THE READINGS THROUGH THE
EYEPIECE.
*** DRY THE GLASS COMPLETELY WHEN YOU ARE
DONE ***
STATION 4
THE SALINITY METER USES THE CONDUCTIVITY OF
THE WATER TO MEASURE SALINITY.
1. MAKE SURE THE PROBE IS IN THE WATER
2. FROM THE OFF POSITION, TURN THE SWITCH ONE
STEP CLOCKWISE TO “RED LINE”
3. IF THE METER DOES NOT GO TO THE RED LINE ON
THE SCALE, ADJUST THE RED LINE KNOB
4. TURN ONCE MORE TO TEMPERATURE. READ THE
TEMPERATURE AND SET THE TEMPERATURE DIAL TO
THE CORRECT NUMBER
5. TURN ONCE MORE TO SALINITY AND READ THE
SALINITY IN o/oo
6. TURN METER OFF
STATION 5
DISSOLVED OXYGEN CAN BE DETERMINED USING A
TITRATION. THE KITS AT THIS STATION ARE DESIGNED
TO GIVE YOU A STEP BY STEP RECIPE FOR
DETERMINING THE DISSOLVED OXYGEN.
FOLLOW THE INSTRUCTIONS FOR SEAWATER IN THE
KIT IN ORDER. REMEMBER TO CLEAN YOUR MATERIALS
BEFORE YOU RETURN THEM TO THE KIT.
WEAR SAFETY GLASSES, AND WASH YOUR HANDS
WHEN DONE.
STATION 6
THIS STATION USES A METER TO DETERMINE
DISSOLVED OXYGEN. WHEN YOU TAKE YOUR READING,
GENTLY MOVE THE PROBE BACK AND FORTH IN THE
WATER TO KEEP THE SAMPLE “FLOWING”