Name _______________________________________
Seawater Chemistry Pre-Lab Exercise
Seawater Chemistry – Salinity Portion
1) Average ocean salinity is about ___________ percent (0/0). This means that if you had a tub of
seawater that weighed 100 pounds and you let it evaporate, __________ pounds of salt would be left
behind, and __________ pounds of water molecules would go into the air. In oceanography, we
usually use parts per thousand instead of percent, and the average salinity of ocean water expressed
this way is __________ parts per thousand (0/00).
2) Your measurements of salinity in water samples in the lab may range as low as ________0/00 to as
high as _________0/00.
3) What are the two main variables that control the density of seawater?
4) What did the demonstration with the salt water and fresh water on the balance scale show?
5) What did the demonstration with the cool water and the warm water on the scale show?
6) What did the demonstration with the light bulb apparatus show?
7) In lab, we will measure water salinity in two ways: by conductivity (how well the water conducts an
electric current) and by refraction (how much light bends as it passes through the water).
a) As water salinity increases, conductivity will (circle one answer):
increase
decrease
b) As water salinity increases, the amount of refraction will:
increase
decrease
c) What’s the point of making the same scientific measurement using two different techniques?
Seawater Chemistry – Dissolved Oxygen Portion
1) The procedure we will use to measure oxygen in water samples is called ___________________.
2) When we conduct this procedure, the more chemical solution (sodium thiosulfate) that we use to
complete the reaction the
more
less
oxygen is in the water. (Circle the correct
answer).
3) What is the number one error students make when making oxygen measurements with this
procedure? How will this error affect your oxygen results?